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Antiferroelectric (AFE) materials are potentially useful for energy storage applications. Lead hafnate (PbHfO 3) is one of the prototypical AFE materials. However, its critical field (E cr) which is needed to induce the AFE to ferroelectric phase transition is close to the dielectric breakdown strength. To reduce E cr , we prepare the solid solutions of (1- x)PbHfO 3 – x BiAlO 3 (x = 0.00–0.04) via solid state synthesis. The crystal structures, dielectric behaviour, ferroelectric properties, and energy storage properties are investigated. A temperature-composition phase diagram is established. At room temperature, the crystal symmetry of all compositions is orthorhombic with the Pbam space group. Upon heating, the transition to the AFE orthorhombic Imma phase is observed at the temperature T C1 , which slightly decreases with increasing x , followed by the transition to the cubic phase at the temperature T C2 , which does not depend on x. Distinct dielectric anomalies are observed at T C1 and T C2. It is found that BiAlO 3 substitution reduces E cr and the polarization–electric field relations display characteristic double hysteresis loops. For x = 0.04, at a comparatively small applied field of 130 kV/cm, the values of recoverable energy density (W rec) and efficiency of 0.24 J/cm3 and 84 %, respectively, are obtained. At 190 °C, a W rec = 0.75 J/cm3 and a very high efficiency of 92 % are obtained at the field of 50 kV/cm. Thus, the prepared material can potentially be used in high-temperature pulsed power capacitors for energy storage applications within the temperature range from room temperature up to 190 °C. [ABSTRACT FROM AUTHOR]

In present work, a novel ceramic composition of (1- x)NaNbO 3 - x Bi 1/3 ZrO 3 was designed to break through the bottleneck that high energy density (W d) and power density (P D) are difficult to coexist for pulse discharge applications. The modified ceramics exhibited well-defined double P-E loops, a high P D of ∼22.5 MW/cm3 and a high W d of ∼0.22 J/cm3 simultaneously, superior to other published works. The structural analysis showed that the unstable antiferroelectric P phase gradually transforms into the stable R phase after Bi 1/3 ZrO 3 modification, mainly due to the great decrease of P–R transition temperature to 175 °C. In addition, P - E and I - E results under large signals further demonstrated the phase transition from P to R phase. Our work provides a significant way to regulate the phase transition of sodium niobate. [ABSTRACT FROM AUTHOR]

In the present work, the investigation of the structural, dielectric, ferroelectric and energy storage properties of polycrystalline samples of (1-x)BaTiO 3 – xEuTiO 3 (BT-ET) solid solution materials prepared by conventional solid-state reaction method has been carried out. X-ray diffraction analyses have revealed the formation of a single-phase tetragonal structure with the P 4 mm space group. Furthermore, the temperature dependence of the dielectric constants marked the presence of the following sequence of structural phase transitions, namely from rhombohedral to orthorhombic, from orthorhombic to tetragonal and from tetragonal to cubic phase transitions with the increase of temperature. A diffuse phase transition has been observed from the dielectric permittivity peak and has been analyzed using the modified Curie-Weiss law and the degree of diffuseness is found to be in the range of 1.16–1.76 due to the existence of different states of polarization. A phase diagram has been established based on the temperature-dependent dielectric permittivity studies. The room temperature ferroelectric properties point to a coercive field larger than that of BaTiO 3 ceramics. Broad dielectric peaks associated with diffuse phase transition appear in a wide temperature range (40–100 °C) with the highest dielectric permittivity ε' = 6498 found in the x = 0.05 ceramics. Moreover, an improved energy storage performance is obtained in the 0.95BaTiO 3 -0.05EuTiO 3 ceramic with a recoverable energy density of W rec = 0.797 J/cm3, coupled with an efficiency η = 73 % at 170 kV/cm and the highest storage energy density of W st = 1.571 J/cm3 is obtained for 0.90BaTiO 3 -0.10EuTiO 3 , which is superior to other lead-free BT-based ceramics. All these features demonstrate that the BT-ET ceramics can be widely used in energy storage applications and also in high-temperature multilayer capacitors for automotive, aerospace and related industries. [ABSTRACT FROM AUTHOR]

Lead-free Bi 0.5 Na 0.5 TiO 3 -SrTiO 3 (BNT-ST) thin films with various thicknesses were deposited on the Pt(111)/Ti/SiO 2 /Si(100) substrates employing a sol-gel technique with a two-step annealing process. Despite the variations in thickness, the films exhibited a consistent polycrystalline structure, evidenced by identical diffraction peaks, albeit with differences in intensity. An imprint became evident in micro-thick films, increasing with film thickness. Also, the emergence of self-polarization was observed in thicker films detected by piezoresponse force microscopy. Noteworthy is the pronounced influence of film thickness on strain response, with the 1.38 μm-thick films demonstrating a large strain of 1.18%. The outstanding strain response can be attributed to the notable contribution of electric field-induced phase transition and polarization dynamics. This work provides a promising potential application of micrometer-thick BNT-ST thin films in advanced actuator devices. [ABSTRACT FROM AUTHOR]

PbZrO 3 (PZO) possesses a unique antiferroelectric-ferroelectric (AFE-FE) phase transition under an external electric field and engages more attention in understanding and regulating the phase transition behavior. In this work, changing annealing temperature (600–750 °C) and ultralow content (5‰) ions doping are used to optimize the phase transition of PZO films via grain size engineering. As annealing temperature increases, the maximum polarization P max increases but forward/backward switching fields E F / E A reduce accompanied by the average grain size enhances from 622 to 686 nm. Following, 5‰ mol aliovalent ion La3+ or K+ doped PZO-650 films both enhance P max and E F / E A indicating the strengthened antiferroelectricity, and meanwhile the grain size enhances to ∼800 nm. A high discharge density of 31 J/cm3 is achieved for 5‰ mol La-doped PZO films at a low electric field of 1 MV/cm, which is ∼100 % higher than those of pure PZO films at different annealing temperatures. This work compares the phase transition characteristics changes in PZO films by changing annealing temperature and ultra-low content ion doping strategy, which would provide new thinking in grain size-engineered antiferroelectric materials for energy storage applications. [ABSTRACT FROM AUTHOR]

BiFeO 3 (BF) based ceramics are inspiring great interest in advanced pulsed power applications owing to their giant spontaneous polarization, meanwhile limited by the significant leakage current. In this work, Sr 0.7 Bi 0.2 TiO 3 (SBT) modified 0.7BiFeO 3 -0.3BaTiO 3 (BF-BT) ternary lead-free relaxor ferroelectric ceramics are investigated to elaborate the dielectric performances, including the impedance, relaxor behavior, ferroelectric and energy storage, and strain properties. The substitution of SBT induces a phase transition from an R 3 c to an average pseudo-cubic structure and forms a secondary phase at high dopants. Simultaneously, the resistivity, electrically homogeneous, and band gaps are increased significantly, related to the inhibition of oxygen vacancy formation. Besides, the ferroelectric long-range order is disrupted, which promotes the formation of local defect fields and polar nanoregions. The structural heterogeneity for the higher doped components leads to an increased relaxation behavior with an almost hysteresis-free polarization response to external electric fields. Excellent temperature-insensitive dielectric response and promising dielectric energy storage properties in low electric fields are achieved, respectively. These results indicate that the SBT modification is an effective route in regulating the dielectric performance of bismuth ferrite based relaxors. [ABSTRACT FROM AUTHOR]

While Mg–Mg 2 Ni composites are promising for hydrogen storage, their implementation is hindered by our incomplete understanding of absorption/desorption kinetics. Here, we combine in situ neutron diffraction with kinetic and microstructural analyses to uncover the sorption mechanism of deuterated hydrogen D 2 in a Mg–Mg 2 Ni composite processed by fast forging. Phase transitions upon first absorption are found to be different from subsequent absorptions. The first absorption involves rapid formation of Mg 2 NiD 0.3- x followed by simultaneous formation of MgD 2 and Mg 2 NiD 4. Kinetic modeling indicates that surface nucleation of the magnesium hydride is rate-limiting. Subsequent absorptions involve two phases, Mg and Mg 2 NiD 0.3- x , which promote absorption. Kinetic modeling and microstructure analysis indicate that (1) MgD 2 nucleation occurs at the Mg–Mg 2 NiD 0.3- x interface and (2) Mg 2 NiD 4 formation is kinetically controlled by deuterium diffusion through the growing Mg 2 NiD 4 plate. In all desorptions, deuterium release starts by rapid decomposition of Mg 2 NiD 4 into Mg 2 NiD 0.3- x , followed by slower MgD 2 decomposition. Please find enclosed the graphical abstract for the manuscript entitled "In situ observation and kinetic modeling of the fundamental mechanisms underlying hydrogen sorption in forged Mg–Mg 2 Ni composites" by Jing Wen, Patricia de Rango, Nathalie Allain, Marc Novelli, Thierry Grosdidier, and Laetitia Laversenne , which we would like to submit for publication in International Journal of Hydrogen Energy. [Display omitted] •Mg–Ni composites have a remarkably fast activation sequence for a bulk material. •The mechanisms of sorption are different from the first hydrogen absorption (activation) as compared to the following ones. •The rate-limiting processes differ depending on the type of reaction (activation, absorption or desorption). [ABSTRACT FROM AUTHOR]

The global community is currently grappling with two significant challenges: climate change and the depletion of non-renewable power sources. To address these issues, scientists are paying increased attention to hydrogen as a potential alternative energy carrier, as it is both ecologically favorable and has the potential to replace non-renewable energy sources. However, scientists face difficulties in storing and transporting hydrogen directly. Perovskite hydrides have gained considerable interest as they exhibit excellent ion exchangeability and high gravimetric hydrogen storage capacity. This study specifically examines the hydrogen storage capabilities of NaAlO 3-x H x perovskite using the famous DFT-based CASTEP simulation code. The research reveals that after hydrogen was inserted into the pristine material, the material's cubic structure along with lattice parameters manifests variation. The study also reveals that the hydrogen-incorporated compositions were structurally and thermodynamically stable, with Born's mechanical stability criteria being fulfilled by all compositions. The ductile or brittle nature of the compounds varied with the amount of hydrogen inserted, as shown by Cauchy's pressure and Poisson's ratio. Additionally, the continuous insertion of hydrogen into the pristine material significantly impacted the electronic states, as demonstrated by the density of states and plots of band gap. After the complete insertion of hydrogen, the band gap fell from 5.86 eV to 0 eV, making the final compound metal, it also affects the material's optoelectronic properties. This research provides detailed insights into optical parameters such as absorption, reflectivity, refractive index, extinction coefficient, complex dielectric function, and energy loss function. The gravimetric storage capacity of the material increased from 0.32 wt% to 5.4 wt% after inserting 100% hydrogen into it. NaAlH 3 is determined to be an excellent material for hydrogen storage based on our conclusions. • An innovative perovskite material for hydrogen storage has been presented. • GGA-PBE approximation was employed in DFT-based calculations. • The formation enthalpies of all compositions ensure their synthesizability. • The hydrogen storage capacity of 5.4% by weight is appropriate for advanced hydrogen storage techniques. • All the compounds are thermodynamically and mechanically stable. [ABSTRACT FROM AUTHOR]

In order to meet the sealing temperature of copper alloy below 1000 °C, a kind of Li 2 O-ZnO-SiO 2 -P 2 O 5 -(B 2 O 3 +Al 2 O 3 +K 2 O) (LZS) glass-ceramics with high expansion coefficient and high resistivity was synthesized via the melting method and then crystallized through controlled cooling. The network structure, thermal properties, crystal phase transition, thermal expansion coefficient, and high-temperature resistivity have been investigated. As the mass ratio of ZnO/Li 2 O increases, the network structure of the LZS glass is strengthened, leading to an increase in the glass transition and crystallization temperature. Moreover, the predominant crystal phases in LZS glass-ceramics transit from Li 2 SiO 3 to Zn[Zn 0.1 Li 0.6 Si 0.3 ]SiO 4 and subsequently to Zn 2 SiO 4. At a ZnO/Li 2 O ratio of 3, a cristobalite phase with a high expansion coefficient emerges. The change in crystal phase results in a variation in the coefficient of thermal expansion (CTE) of glass-ceramics, ranging from 13.2 to 11.2 × 10−6 K−1. At a ZnO/Li 2 O ratio of 3, the softening temperature of glass-ceramics is minimized. Moreover, as the ZnO/Li 2 O mass ratio increases, the resistance of crystallized glass decreases first and then increases. The maximum resistivity is achieved at a ZnO/Li 2 O mass ratio of 5. By optimizing the mass ratio of ZnO/Li 2 O, it is determined that when the mass ratio of ZnO/Li 2 O is 3, the CTE is 12.4 × 10−6 K−1, and the softening temperature (Ts) is 679.8 °C, which is the best material for sealing applications. [ABSTRACT FROM AUTHOR]

The present study is a continuation of our previous work, where we synthesized and characterized t-ZrO 2 nanocrystals through the combustion method. Further, t-ZrO 2 nanocrystals are annealed at 600, 900, 1200, and 1400°C and characterized through XRD, Raman, FESEM, XPS, photoluminescence (PL), and thermoluminescence (TL) techniques. XRD and Raman patterns reveal that the as-synthesized ZrO 2 nanocrystals exhibit a tetragonal phase, and annealing at different temperatures induces phase transformations. Annealing at 600 °C restores the metastable nature of the tetragonal phase, although monoclinic nucleation is visualized through Raman spectroscopy. Annealing at higher temperatures leads to a complete transformation into the monoclinic phase. FESEM micrographs reveal extensive crystal growth and consolidation upon annealing. XPS analysis shows a reduction in the binding energies of the Zr 3d doublet due to the removal of lattice oxygen and the formation of oxygen vacancies upon annealing. The annealing of the synthesized material at 1400 °C induced a transformation to ferromagnetic behaviour at 300 K, with increased saturation magnetization (Ms) and coercivity (Hc), reflecting the stabilization of magnetic ordering and residual defects in the grain boundary. PL responses confirm the formation of luminescent defects in the crystal lattice. The TL response varies with the crystalline phase, annealing temperature, and radiation dose, suggesting defect creation, migration, and localization in the lattice. Overall, the study provides valuable insights into the structural and optical properties of ZrO 2 nanoparticles annealed at different temperatures. [ABSTRACT FROM AUTHOR]

"Boro-mullite" is the name for mullites produced through the synthesis of boron-rich material and playing a critical role in producing high-performance materials. Also, the stability of the anatase phase in the glaze and against temperature has been addressed and improved by many studies. In situ boro-mullite crystals generated using various glass-ceramic glaze compositions that contain TiO 2 and their impact on the transformation of anatase into a rutile phase were examined in this study. Additionally, the samples' water absorption, bulk density, apparent porosity and shrinkage, Vickers hardness, and optical properties were evaluated at various Al 2 O 3 and B 2 O 3 amounts at 700 °C, 800 °C, 900 °C, 1000 °C and 1100 °C. X-ray diffraction analysis revealed that as the temperature and Al 2 O 3 ratio rose, it triggered the boro-mullite phase formation. On the other hand, increasing the Al 2 O 3 ratio led to a rise in the samples' sintering temperature and delayed the anatase to rutile phase transformation. Furthermore, the presence of corundum crystals retarded the anatase crystal size growth during the remodelling process of the conversion of anatase to rutile. While the increase in the B 2 O 3 ratio sharpened the peaks of albite crystals, the formation of rutile crystals accelerated with the increase in temperature and caused inhibition of albite formation. The albite phase's presence facilitated the creation of the liquid phase and achieved the 0.010 % water absorption and 0 % apparent porosity values as well the highest bulk density and microhardness with 2.476 g/cm3 and 550 H V. The yellowness (+b∗) values were found to be the highest at 1100 °C where the rutile crystals reached their maximum size. The anatase-rutile conversion is postponed and the increase in the yellowness value is prevented by the glaze's formation of boro-mullite. FESEM-EDS analysis showed that the temperature was the driving force in the transformation of acicular boro-mullite crystal into highly acicular prismatic needle crystal and spherical anatase crystals into the rod shape rutile. [ABSTRACT FROM AUTHOR]

Ceramic compounds BaTi 1-x Fe x O with x = 0–0.2 prepared by solid state reaction technique were studied using X-ray diffraction, Raman spectroscopy, and magnetometry methods focusing on the correlation between the structure and magnetic properties. Chemical doping with Fe ions leads to a concentration driven structural transformation from the single phase tetragonal (T-) structure to the hexagonal (H-) structure with a mixed structural state stable in the concentration range 0.06 < x ≤ 0.2. Increase in the Fe ions content causes a stabilization of weak ferromagnetic state driven by the exchange interactions Fe3+ – O – Fe3+ ions strongly dependent on the structural positions of the Fe ions. Increase of the dopant content above x = 0.08 leads to a decrease of the remnant magnetization which is mainly caused by a stabilization of Fe4+ ions as well as by the lattice defects associated with oxygen vacancies formed to keep electroneutrality of the compounds. The results of the structural and magnetization measurements allowed to itemize the type of exchange interactions between Fe ions residing different structural positions of the hexagonal lattice as well as to reveal structural instability of the T- and H- phases under ambient conditions and applied electric field which shows a possibility to control the structure and magnetic properties of the mixed compounds via external stimuli. [ABSTRACT FROM AUTHOR]

• Environmental responsible new materials. • Utilization of agricultural residues for refrigeration applications. • Computational simulation of avocado seed oil as a phase change material. • Performance analysis of the avocado seed oil as a phase change material. Bio-based phase change materials (BPCMs) derived from agro-industrial residues represent an ecofriendly alternative for refrigeration applications. In this work, a BPCM was obtained by steam extraction from avocado seed and studied as a suitable cold thermal energy storage system. First, differential scanning calorimetry was used to determine that the solid-liquid phase transition occurred from -27°C to 15°C. This temperature range is of interest for the conservation different food products. The study aimed to determine the best distribution of the material, which was stored in plastic packaging bags, and placed in an insulated polystyrene thermal container. Two configurations were evaluated: (i) four bags of 75 mL, (ii) two bags of 75 mL and one of 150 mL. The temperatures of the avocado seed oil, and of the air inside the container, were measured during 6 to 8 h. It was concluded that, despite working with the same amount of avocado seed oil (300 mL) in different experiments, there was a better performance when the same volume of material was distributed in each wall. Furthermore, the utilization of avocado seed oil allowed to maintain low temperatures, suitable for food preservation during two additional hours. In the same way, in a yogurt storage experimentation of 8 h, the utilization of the avocado oil enhanced the temperature preservation by 6°C on the phase change range from 4°C to 14°C. While compared to water, the temperature difference was evaluated showing a good performance of the BPCM and an important stability on the temperature heating rate. [ABSTRACT FROM AUTHOR]

Electrocaloric (EC) refrigeration offers superior energy-conversion efficiency, miniaturization, and environmental benefits compared to compression refrigeration. However, its practical application is limited by the challenge of aligning the adiabatic temperature change (Δ T) with the operational temperature range. In this study, we have tailored the EC characteristics of BaTiO 3 (BT)-based Ba(Ti 0.9 Sn 0.1)O 3 (BTS) ferroelectric ceramics using Bi(Mg 0.5 Ti 0.5)O 3 (BMT). We provide a comprehensive analysis of the microstructure, electrical properties, and EC behavior of the (1– x)BTS- x BMT system. Our results indicate that the incorporation of BMT establishes a broad platform in the dielectric spectrum while maintaining high polarization. This improvement potentially increases the electrocaloric effect (ECE) and expands the operating temperature range. Direct heat flux measurements reveal that the x = 0.02 composition achieves a maximum Δ T (Δ T max) of 0.41 K with a temperature span (T span) of 68 °C under an intermediate electric field of 50 kV/cm. Moreover, the x = 0.01 sample exhibits a room-temperature Δ T of 0.33 K and relatively good temperature stability within 30–130 °C. These findings indicate that chemical modification methods have the potential to optimize the cooling capacity of refrigerants. [ABSTRACT FROM AUTHOR]

In the case of low-temperature fabrication aiming at transparent polycrystalline YAG ceramics with fine grain size, it is easy to retain trace amounts of the intermediate YAP phase, thereby reducing the optical transmittance. To address this issue, adding a small amount of Al 2 O 3 to the starting YAG powder was found to promote the transformation of the residual YAP phase to the YAG phase at low temperatures. The study investigated the effect of sintering temperature and excess Al 2 O 3 amount on preparing transparent YAG ceramics by hot pressing. The transmittance of the Al 2 O 3 -aided single-phase YAG ceramic (2 mm thick) prepared using the two-step sintering reached 43.4 % at 400 nm and 71.8 % at 1064 nm, with a grain size of about 2 μm, while the transmittance of the multiphase YAG ceramic without Al 2 O 3 addition was less than 1 % at both wavelengths. [ABSTRACT FROM AUTHOR]

Antiferroelectric (AFE) materials have great potential for applications in large-strain actuators due to their unique field-induced phase transition properties. In particular, AFE ceramics that exhibit a high level of field-induced strain with reversible and "on/off" features at low electric fields are well suited for use in reliable actuators. In this study, we designed Pb 0.97 La 0.02 (Zr 0.72-x Sn 0.17+x Ti 0.11)O 3 (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) AFE ceramics with the components close to the morphotropic phase boundary (MPB). The polarized Pb 0.97 La 0.02 (Zr 0.60 Sn 0.29 Ti 0.11)O 3 AFE ceramics exhibit an excellent field-induced strain of 1.21 % at a low electric field (60 kV/cm). This phenomenon can be attributed to the more miniaturized and disordered domain structure, which provides an important contribution to its field-induced strain beyond the AFE-FE phase transition. This work not only provides an AFE ceramic candidate for actuators but also explains the origin of the excellent field-induced strain properties of AFE ceramics with components close to the MPB. [ABSTRACT FROM AUTHOR]

The enhanced high-power performance of 0.93 Pb(Zr 1-x Ti x)O 3 -0.05 Pb(Mn 1/3 Sb 2/3)O 3 -0.02 Pb(Sc 1/2 Nb 1/2)O 3 (x = 0.48, 0.50, 0.52, 0.54, 0.56) piezoelectric ceramics (PZT-PMS-PSN) has been achieved with notable improvement in the piezoelectric coefficient (d 33). The presence of the monoclinic phase (C c) has led to an increase in d 33 from 214 pC N−1 to 315 pC N−1. Therefore, the composition 0.93 Pb(Zr 0.48 Ti 0.52)O 3 -0.05 Pb(Mn 1/3 Sb 2/3)O 3 -0.02 Pb(Sc 1/2 Nb 1/2)O 3 exhibits excellent mechanical and electrical parameters: a d 33 value of 315 pC N−1, a high mechanical quality factor of 1578, an electromechanical coupling factor k p of 52 %, and a low dielectric loss tanδ of only 0.288 %. Additionally, this ceramic exhibits a significantly high Curie temperature (T c), reaching up to 328 °C which stabilizes its ferroelectric phase. Moreover, the phase transition of PZT-PMS-PSN ceramics from rhombohedral to tetragonal phase was investigated by X-ray diffraction, Raman scattering, Piezo-response force microscopy. [ABSTRACT FROM AUTHOR]

[Display omitted] This study introduces a novel artificial intelligence (AI) force field, namely a graph-based pre-trained transformer force field (GPTFF), which can simulate arbitrary inorganic systems with good precision and generalizability. Harnessing a large trove of the data and the attention mechanism of transformer algorithms, the model can accurately predict energy, atomic force, and stress with mean absolute error (MAE) values of 32 meV/atom, 71 meV/Å, and 0.365 GPa, respectively. The dataset used to train the model includes 37.8 million single-point energies, 11.7 billion force pairs, and 340.2 million stresses. We also demonstrated that the GPTFF can be universally used to simulate various physical systems, such as crystal structure optimization, phase transition simulations, and mass transport. The model is publicly released with this paper, enabling anyone to use it immediately without needing to train it. [ABSTRACT FROM AUTHOR]

The layered N-doped tungsten carbide (WC) with enhanced electrical conductivity was designed and fabricated via a facile molten-salt-chemistry-assisted strategy as electrocatalytic material for efficient hydrogen evolution reaction (HER), which is a prospective and feasible approach for green and carbon-neutral hydrogen energy storage. The layered WC structure was in situ formed via carbonization procedure utilizing the as-prepared WO 3 microspheres as substrates. The microstructure, physicochemical properties, and electrocatalytic HER performance of WC catalysts can be regulated by the treatment temperature ranging from 700 to 1000 °C during the molten-salt-chemistry-assisted processes with NaCl/KCl mixture as the molten salt. The engineered WC/C-900 catalyst with optimized components of W, C, and N elements, synergistic effect, and enhanced electrical conductivity provides high HER performance with an overpotential of 188 mV (684 mV of WO 3) and long-term 28 h stability at 10 mA cm−2 in acidic medium. Additionally, in-depth insights into the catalyst microstructure, temperature-dependent phase transition, surface/interface properties, structure-activity relationships, and HER mechanism of the versatile material on the basis of theoretical calculation and experimental discovery are also investigated. • The layered WC is fabricated by a facile molten-salt-chemistry-assisted strategy. • Carbonization temperatures can regulate physicochemical properties of WC catalysts. • WC/C-900 displays enhanced electrical conductivity and synergistic effect. • The WC/C-900 catalyst exhibits high HER performance and long-term stability. [ABSTRACT FROM AUTHOR]

Efficient hydrogen production via anion exchange membrane water electrolysis depends on hydrogen evolution reaction (HER) electrocatalysts with excellent kinetics in alkaline electrolytes. Amorphous alloys offer enhanced electrochemical properties and improved corrosion resistance, making them attractive candidates. Among these, the bimetallic nickel molybdenum (NiMo) alloy stands out as one of the most active transition-metal-based HER electrocatalysts, available in both amorphous and crystalline forms. This study investigates the influence of thermal annealing temperature in a reducing environment on the phase change and electrochemical properties of hydrothermally grown 1-dimensional (1D) NiMo nanorods. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that lower annealing temperatures resulted in a mixed amorphous and crystalline phase of NiMo, while higher temperatures led to increased crystallinity and a decrease in the amorphous fraction. Electrochemical analysis indicates that the amorphous NiMo annealed at 400 °C exhibits overpotentials as low as 31 and 115 mV at 10 and 100 mA cm−2, respectively, outperforming several similar electrocatalysts reported in the literature. This enhanced activity is attributed to improved electron and mass transport, along with increased exposure of active sites in the amorphous phase. Thus, there is a clear relationship between annealing conditions and the formation of amorphous NiMo, which exhibits excellent HER properties and durability. • Amorphous-crystalline NiMo alloy enhances HER kinetics in alkaline electrolytes. • Lower annealing temperatures yield amorphous characteristics of NiMo with superior HER activity. • NiMo annealed at 400 °C achieves 31 mV overpotential at 10 mA cm−2. • Amorphous state boosts electron transport and active site exposure. • Tailored annealing links to NiMo's excellent HER properties and durability. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are emerging as efficient oxygen evolution reaction (OER) electrocatalysts due to their structural advantages and compositional flexibility. Despite their promise, Mn-based LDHs are hampered by poor conductivity, limiting their OER efficacy. This research introduces a hydrothermal and chemical etching technique to fabricate NF/NiMn LDH@NiMnFe(OH) x structures, significantly improving OER performance. The study reveals that integrating Fe3+ into the NiMn LDH fosters a synergistic Ni–Fe interaction, markedly boosting electrocatalytic efficiency. The NF/NiMn LDH@NiMnFe(OH) x -90 shows a low overpotential of 250 mV at 10 mA cm−2 and a Tafel slope of 49.9 mV dec−1 in 1 M KOH, surpassing both its NM precursor and other Ni-based LDH catalysts, including commercial RuO 2. In situ, Raman spectroscopy indicates a pivotal phase transition in NF/NiMn LDH@NiMnFe(OH) x to NiOOH at elevated potentials, essential for OER activity. Raman peaks at 463 and 585 cm−1 confirm this structural evolution. The OER activity boost is attributed to increased oxygen vacancies and enhanced conductivity. Moreover, NF/NiMn LDH@NiMnFe(OH) x -90 maintains stability with negligible degradation after 24 h, underscoring its durability. These findings offer a strategic approach to designing high-performance OER electrocatalysts, leveraging nickel-based layered double-metal oxides for potential water-splitting applications, and emphasize the significance of surface engineering and compositional tuning. • The catalyst with high activity and stability was constructed by a simple method. • Important insights for the design of heterophase electrocatalysts is proposed. • In situ Raman reveals key phase transition to NiOOH at elevated potential. • Fe etching increases oxygen vacancy and conductivity, thus increasing OER performance. [ABSTRACT FROM AUTHOR]

This paper reports an extensive investigation on the structural, dielectric, ferroelectric and pyroelectric properties of 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 (x = 0.0, 0.5, 0.6, 0.7) ceramics synthesized via conventional solid-state reaction (SSR) technique. X-ray diffraction data confirms the presence of pure perovskite phase. The variation of lattice parameters with strontium concentration in 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 ceramics were evaluated using the Rietveld refinement of the XRD data. The variation of dielectric permittivity with temperature (ε' ∼ T) shows the diffused phase transition and all the parameters related to the relaxor ferroelectrics (relaxation coefficient, activation energy and freezing temperature) were evaluated. The energy storage properties of the as-prepared ceramics were evaluated using the room temperature PE loop. Amongst the as-prepared ceramics, the composition with x = 0.5 possesses the highest energy storage density of 0.46 J/cm3 with an efficiency of 90 %. The temperature dependent P-E loops were used to study the electrocaloric effect (ECE). The ECE calculations were performed using in-direct method based on Maxwell's thermodynamic relations. A maximum adiabatic temperature change of 0.32 K is achieved at 268 K under a small applied electric field of 25 kV/cm for the ceramic with Sr content x = 0.5. Additionally, electrocaloric responsivity ξ max = 0.13 K mm/kV was also found for the studied ceramics. The above results show that the ceramic 0.7Ba 1-x Sr x TiO 3 – 0.3Bi 0.5 Na 0.5 TiO 3 with the composition x = 0.5 is a viable lead-free option for application in solid state refrigeration. [ABSTRACT FROM AUTHOR]

The polycrystalline Sr 0.8 Sn 0.2 Bi 1.75 Nd 0.25 Nb 2 O 9 (NdSBN) was synthesized using the green synthesis microwave sintering method, which significantly reduced the processing parameters of the NdSBN ceramics. Orthorhombic crystal structure with A2 1 am symmetry was revealed by Rietveld refinement study, whereas the doping-induced strain and crystallite size was studied using the Williamson Hall method. Crossectional SEM micrographs confirm the plate-like structure, with an average grain size of 273.7 nm. A diffuse type of phase transition was observed at 345 °C, which usually arises due to compositional fluctuations and mobile oxygen vacancies; further, the diffusiveness of the NdSBN was studied using Uchino and Nomura function, a modified version of Curie-Weiss law (CW). The frequency and temperature-dependent dielectric study of NdSBN ceramics display a Maxwell-Wagner relaxation with a high loss in a low frequency regime, possibly due to the presence of leakage current in the solid solution. Frequency dependent AC conductivity obeys Jonscher's power law, whereas DC conductivity supports polaron assisted hopping in NdSBN composition with dual activation energies of 0.55 eV and 0.75 eV, which correspond to electrons and ions, respectively. The non-Debye type relaxation mechanism in conjunction with negative temperature coefficient of resistance (NTCR) behavior was demonstrated by temperature dependent impedance spectroscopy, while modulus spectroscopy confirmed the multiple relaxation processes in NdSBN ceramics. [ABSTRACT FROM AUTHOR]

This study establishes an optimization protocol to fabricate a stoichiometric VO 2 thin film onto the glass substrate using a single process step in RF magnetron sputtering. An interplay between the substrate temperature and the oxygen-to-argon ratio in process gas is shown to achieve a range of VO x composition (from oxygen-rich to oxygen-deficient phases). The re-sputtering phenomenon is found to be crucial at higher temperature (T ≥ 873 K), leading to a shift in stoichiometry from V 2 O 5 to V 2 O 3. Moreover, a process model for the fabrication of various VO x compounds in thin film form is also established in this study. The crystal structure transformation from M 1 to R phase for these VO 2 thin films deposited over a range of process conditions is found to be 339 ± 1 K, in close agreement with the reported value for the bulk VO 2. In spite of the microstructural variations, these films are found to show consistent phase transition behavior, excellent stability, and reliability in repeated thermal cycles. These films show a semiconductor-to-metal transition, which is correlated to their structural phase transformation temperature. Moreover, this study also establishes a correlation between various external stimuli, widening the usage of this material in a range of applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Bi 0.5 Na 0.5 TiO 3 -based ferroelectric ceramics have broad application prospects due to their excellent electrical properties and are considered to be one of the most promising functional materials to supersede lead-based materials. Here, 0.9Bi 0.5 Na 0.5 TiO 3 -0.1Bi 0.2 Sr 0.7 TiO 3 - x NaNbO 3 (BNT-BST- x NN) ternary lead-free ferroelectric ceramics were prepared, and the origin of their excellent dielectric properties was investigated in terms of phase boundary and domain structure. The introduction of NN led to a phase transition from the ferroelectric rhombohedral phase (R 3 c) to the relaxor tetragonal phase (P 4 bm), and the two phases coexisted in the BNT-BST- x NN ternary solid solution with x ranging from 0.06 to 0.2. Meanwhile, the macroscopic domain of BNT-BST was destroyed and replaced by highly active polar nano-regions (PNRs) of the P 4 bm phase, leading to an increase in local structural disorder and enhanced relaxor behavior. A dielectric constant (ε r) of ∼1765 (150 °C) with Δ ε / ε 150 °C less than 15 % over a broad range from 80 to 328 °C was achieved in the BNT-BST-0.15NN, and an excellent energy storage property (W rec = 3.3 J/cm3) was obtained under a low electric field (190 kV/cm). More specifically, the relationship among phase boundary, domain structure, and excellent electrical properties was achieved based on Rietveld refinements and the dielectric/ferroelectric characterizations. This work provides a deep insight into the phase evolution and its impact on the electrical properties of the BNT-based relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

The FeTiO 3 nanopowder is a vital engineering material known for its exceptional performance in energy generation, storage, electrochemical sensors, and catalysis. However, synthesizing FeTiO 3 nanopowder with high crystallinity and phase purity typically requires specialized equipment and controlled heat treatment due to the instability of Fe2+ ions. Using the one-step solution combustion synthesis (SCS) method, FeTiO 3 nanopowder withe high crystallinity were successfully produced utilizing basic equipment. Additionally, the influence of carbon additives on phase transitions, as well as the physical and physicochemical properties of the synthesized powder, was examined. XRD results indicate that increasing the amount of fuel, particularly glycine, creates a stable environment for the crystallization of FeTiO 3 nanoparticles. Moreover, enhancing the carbon content in precursor solutions with urea enhances reduction conditions and boosts the stability of FeTiO 3 in the final product. The presence of carbon additives in glycine-fuel samples leads to unfavorable outcomes by increasing the levels of TiO 2 and Fe 3 O 4 undesirable phases. Incorporating additive carbon into the urea-synthesized precursor solution resulted in a particle size increase exceeding 50 nm and raised the combustion temperature by a minimum of 230 °C. Furthermore, the presence of 15 wt% additive carbon in the sample synthesized with glycine improved the specific surface area of particles from 2.44 m2/g to 18.41 m2/g. Obtained results have shown that achieving high crystallinity of FeTiO 3 nanopowder is feasible through a one-step solution combustion synthesis process. This can be accomplished by carefully choosing the synthesis conditions, such as the type and quantity of fuel, along with the carbon additive. [ABSTRACT FROM AUTHOR]

This research investigated the application of municipal solid waste incineration fly ash (MSWIFA), municipal solid waste incineration bottom ash (MSWIBA), and construction waste residue (CWR) as raw materials for the comprehensive conversion into municipal solid waste ceramics employing the SiO 2 -Al 2 O 3 -CaO-MgO (8 wt%) phase diagram. This study aimed to evaluate the influence of the addition of MSWIFA and sintering temperature on important ceramics properties, including linear shrinkage, water absorption, sintering range, and flexural strength. Additionally, relationships were established among these physical parameters using Pearson's correlation coefficient. The thermal behavior of the mixture was analyzed through automatic slag melting point tester and TG-DSC techniques. Furthermore, characterization of the crystalline phase transition and microstructure of sintered samples was performed by XRD, Factsage, and SEM. The results showed that both the addition of MSWIFA and the sintering temperature significantly influenced the crystal phase composition of the sintered ceramics. Moreover, the addition of MSWIFA and the sintering temperature had a significant influence on the pore structure of the ceramics. These ceramics exhibited exceptional properties, such as the extremely low water absorption rate of 0.08 % and the remarkable flexural strength of 124.78 MPa. Ceramics performance indicators were far higher than the requirements of China's national standard GB/T4100-2015. The sintering range had the capability to attain 30 °C, guaranteeing the feasibility of practical manufacturing processes. Furthermore, leaching concentration tests conducted on additive-free ceramic samples reveal a low risk of heavy metal contamination, as the heavy metals were effectively solidified within the crystalline and amorphous phases of the ceramics. The comprehensive utilization of MSWIFA, MSWIBA, and CWR for the production of fully solid waste ceramics not only yields cost reduction benefits but also promotes efficient utilization, presenting a feasible and highly promising approach to sustainable waste management. [ABSTRACT FROM AUTHOR]

The extensive utilisation of zeolite catalysts in contemporary industries has resulted in the generation of considerable quantities of zeolite waste. The recycling of zeolite wastes for the preparation of highly crystalline mullite whiskers remains a significant research challenge. Mullite whiskers are often employed as enhancing the mechanical properties of ceramic matrix composites. In this study, we successfully synthesized mullite whiskers under the catalytic condition of 650 °C, utilising zeolite waste as the reaction source and MoO 3 as the liquid-phase catalyst. The XRD and SEM results indicate that the phase transition direction of the zeolite waste is influenced by the MoO 3 content and the sintering temperature. The powder mixture (M8-800), containing 8 wt% MoO 3 and subjected to a sintering temperature of 800 °C, exhibited the highest aspect ratio (22.89 ± 2.31). The synthesis of mullite whiskers via a low-temperature liquid-phase reaction mechanism is demonstrated by TEM experiments. The precursor droplets, comprising the catalyst and glass melt, serve as the initial material for whisker growth. This study proposes a novel and feasible solution for industrial waste recycling. • Exploring the phase transition between zeolite waste, Lazurite 1C, Albite low and mullite. • The interfacial engineering of the glass layer/mullite is discussed, and mullite follows a liquid-solid growth mechanism. • Exploring the industrial prospects for the preparation of mullite whiskers from zeolite wastes. [ABSTRACT FROM AUTHOR]

Perovskite oxide Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3‒δ (BSCF) is a highly active cathode material widely studied for intermediate temperature solid oxide fuel cells (IT-SOFCs), however, the tendency of phase transition of BSCF under IT-SOFC operating conditions poses a critical challenge for its reliable applications. Here, a multiphase BSCF-Gd 0.1 Ce 0.9 O 1.95 (GDC) nanocomposite with heterogeneous interfaces is synthesized at a relatively low calcination temperature of 750 °C. Both the multiphase composition and microstructural morphology of the nanocomposite are very stable during annealing at 750 °C. The unique multiphase structure and ultrafine microstructure of the nanocomposite can be maintained in the resultant cathode through a sintering-free direct assembly fabrication method. As a consequence, a corresponding single cell based on the BSCF-GDC nanocomposite cathode generates a maximum power density of 1.41 W cm−2 at 750 °C with outstanding galvanostatic stability for 100 h. This work provides an effective means for the design and utilization of highly active BSCF-based nanocomposite cathodes for durable IT-SOFCs. [ABSTRACT FROM AUTHOR]

This work reported the influence of laser surface melting (LSM) pretreatment on the growth behavior, electrical insulation and corrosion resistance of plasma electrolytic oxidation (PEO) film on 6061 aluminum alloy. It is found that the LSM pretreatment refines the surface structure of original Al metal, generating defects that store excessive energy, thereby enhancing reaction kinetics and phase transition during the PEO process. By LSM pretreatment, uniform electrical discharge and film growth can be obtained, resulting in fewer defects and lower porosity in PEO layers. Additionally, a large amount of columnar crystals comprising of SiO 2 phase are observed, which transformed from the SiO 3 2− deposited on the surface, and the LSM pretreatment significantly improves the electrical insulation, corrosion resistance, and substrate adhesion of following PEO layer. Under the same PEO treatment duration, the breakdown voltage of coating increased by 100 V, and icorr decreased from 3.26 × 10−4 to 9.13 × 10−6 A cm−2. It is expected that the combination of LSM and PEO processes can not only enhance the surface properties of Al metal, but also expand the practical application of aluminum alloy in high-power electronic devices and related fields. [Display omitted] [ABSTRACT FROM AUTHOR]

Antiferroelectric (AFE) ceramic dielectrics are widely recognized for their high potential in high-power pulse equipment applications. Lead-free NaNbO 3 (NN) antiferroelectric ceramics have emerged as a prominent research topic in the field of energy storage due to their abundant phase structure, affordability, and moderate bandgap. The metastable ferroelectric Q phase results in a square hysteresis loop for NN at room temperature. However, 0.96NaNbO 3 -0.04 CaZrO 3 (NNCZ) exhibits a typical double hysteresis loop at room temperature with the main crystalline phase being the antiferroelectric P phase, which has poor energy storage performance. In this study, Bi 0.5 Na 0.5 TiO 3 (BNT) is used to optimize the energy storage performance and stabilize the P phase in NNCZ simultaneously. The dielectric constant and temperature-dependence XRD results that from −100 °C to 350 °C, x = 0.05 undergoes a phase transition from AFE P to AFE R and then to PE S. The solid solution of BNT decreased the sintering temperature of NN-based ceramics and decreased average grain size, thereby facilitating domain size reduction and improving the sample's energy storage efficiency from ∼30 % to ∼60 %, with an effective energy storage density reaching 1.51 J/cm3. The above results demonstrate that enhancing energy storage efficiency can be achieved through component design by reducing average grain size. [ABSTRACT FROM AUTHOR]

After the invention of indoor tabletop shock tubes, studies on the impact of low-pressure acoustic shock waves on materials have been sufficiently conducted and found several spectacular phase transitions. However, the acoustic shock wave impact studies on minerals remain unexplored. The floodgates are to be opened by streamlining a systematic approach in bringing out a new era of spectacular findings as more and more minerals are involved in the investigation. Hence, in the present investigation, we have chosen one of the most prominent upper mantle earth minerals of α-Olivine (forsterite-Mg 2 SiO 4) single crystal for the ex-situ shock wave recovery experiment with 2.0 MPa transient pressure. Raman spectroscopic technique has been utilized to examine the crystallographic stability of the title mineral. The observed shock-wave impact results demonstrate that the forsterite remains to be in the crystallized state maintaining the same space group of P bnm, however, significant changes have been witnessed in the normalized intensity ratio of the characteristic doublet Raman peaks of the forsterite (asymmetry stretching SiO 4 (824 cm−1)/symmetry stretching SiO 4 (855 cm−1) such that the values are found to be 2.17, 2.27, 1.38, 0.51, and 2.43 against the number of shock pulses of 0, 1, 2, 3 and 4, respectively. It is to be noted that, we have found more pronounced changes in the doublet Raman peak intensity compared to the flat plate accelerator shock compression experiment on forsterite (Tielke et al., J. Geophys. Res. Planets (2022)) and the observed values are 0.8, 0.3, 0.6, 0.8 and 0.52 for 0, 21.3, 22.4, 38.9 and 41.8 GPa, respectively without undergoing any structural transitions towards the high-pressure phases. Based on the assessment of comparative results, tabletop shock-tubes can be strongly considered for mineralogical research to expand the current knowledge on the behaviors of the earth and space minerals under extreme-conditions. [ABSTRACT FROM AUTHOR]

Ba 0.87 Ca 0.13 (Ti 0.9 Zr 0.1) 0.98 (Zn 1/3 Nb 2/3) 0.02 O 3 ceramic was prepared using a solid-state reaction method. This work investigates their dielectric, ferroelectric, energy storage, and electrocaloric properties. X-ray diffraction analysis confirms a pure perovskite structure. The dielectric constant reaches a maximum of 9364 at 326 K. Enhanced total energy density, recovered energy density, and energy storage efficiency are observed between 303 K and 363 K. Artificial neural networks (ANNs) are employed for the indirect determination of large ECE and responsivity based solely on measured ferroelectric polarization (P(E,T)). This approach offers rapid and accurate predictions with minimal experimental data, significantly accelerating the characterization of novel electrocaloric materials. The maximum ECE occurs above the Curie temperature (T C) and increases with higher electric fields. The ceramic exhibits significant ECE parameters around TC with a broad electrocaloric temperature span. Various figures of merit, including relative cooling power, refrigerant capacity, and temperature-averaged entropy change, are explored under different electric fields, demonstrating the material's potential for green cooling devices. These figures improve monotonically with increasing field strength. A comprehensive analysis of the field dependence of ΔS (entropy change) confirms the second-order nature of the electric phase transition through master curve analysis. In conclusion, these lead-free ceramics exhibit promising applications in high-performance energy storage devices and solid-state refrigeration technology. [ABSTRACT FROM AUTHOR]

This study explored the structural, vibrational, morphological, optical, and magnetic characteristics of both as-grown and annealed single crystals of tin telluride (SnTe), employing diverse analytical techniques. X-ray powder diffraction (XRD) analysis shows the cubic lattice structure of SnTe with consistent lattice parameters across different temperatures, along with the phase transition phenomenon. Fourier Transform Infrared Spectroscopy (FTIR) elucidates temperature-induced shifts in vibrational modes, indicating sensitivity to thermal stimuli. Scanning electron microscopy (SEM) reveals layer-by-layer growth patterns and temperature-dependent variations in crystal morphology. Energy-dispersive X-ray analysis (EDAX) confirms the synthesized crystals' high purity and slight tellurium-rich composition. Optical band gap measurements demonstrate an increase in band gap upon annealing, attributed to valence band convergence. Field-dependent magnetization (M − H) curves exhibit ferromagnetic properties at ambient temperature, which escalate with increasing annealing temperature. Electron Paramagnetic Resonance (EPR) spectra reveal spin mobility and exchange coupling, with variations in the g-factor suggesting the presence of additional spin entropy. These observations offer significant insights into the complex properties of SnTe, which are crucial for its potential applications across various technological fields. [ABSTRACT FROM AUTHOR]

Polymer-based ferroelectric composites, particularly those containing Poly (vinylidene fluoride) (PVDF), have emerged as preferred materials for flexible electronics and sensors owing to their excellent electro-mechanical attributes and ease of fabrication. The efficacy of PVDF composites is significantly influenced by the fillers and the proportion of the β-phase present. This research details the synthesis of La 0.7 Ba 0.3 MnO 3 (LBMO) particles via solid-state reaction, surface-functionalized with acetic acid, and subsequently introduced as nucleating agents into Poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to fabricate LBMO/P(VDF-HFP) composite membranes. The LBMO fillers before modification significantly increased the β-phase content from 32.7 % to 87.8 % in 5 wt% unmodified LBMO/P(VDF-HFP) membranes. After modification, the hydroxyl groups attached to acetic acid-modified LBMO form hydrogen bonds with -CF 2 groups in P(VDF-HFP), inducing the formation of the β phase while enhancing macroscopic polarization and piezoelectricity. At a 7.5 wt% acetate-modified LBMO doping level, the composite membrane exhibits a β-phase content of 64.5 %, but concurrently enhancing the film's dielectric properties. At 103 Hz, the dielectric constant of 5 wt% modified LBMO/P(VDF-HFP) membrane increases to 24.8, with a minimal rise in dielectric loss from 0.0293 to 0.0314. Moreover, under a 10 N compressive load at 1 Hz, the 5 wt% modified LBMO/P(VDF-HFP) composite achieves an open-circuit voltage of 4.3 V. These improved dielectric and piezoelectric properties indicate the composite's suitability for energy harvesting applications. [ABSTRACT FROM AUTHOR]

The lead metaniobate (PbNb 2 O 6 , PN) with high Curie temperature is widely used to fabricate transducer for high-temperature application up to 300 °C. However, evident dielectric anomalies and direct-current resistivity degradation were experimentally observed in PN-based ceramics at high temperature, which may significantly restrict the working temperature range for well logging application. When the sample was heat-treated at 260 °C for 3 h in silicon oil, the dc-resistivity of ceramics at 260 °C decreased from 3.8 × 108 to 1.0×107 Ω⋅cm, accompanied by 43 times increase in tan δ at 1 kHz. To investigate the cause of these phenomena, the in-situ piezoelectric, dielectric properties and dc-resistivity were systematically investigated in the samples subjected to heat-treatment at 260 °C in silicon oil. It is revealed that the porous structure of PN-based ceramics allows for the infiltration of silicon oil as a minor phase, and the accumulation of its decomposers within the pores would exert significant influence on the dielectric property and dc-resistivity of ceramics at elevated temperatures. However, the samples still demonstrate excellent thermal stability in piezoelectric property, with value of k t maintaining 0.39 at 260 °C in oil. In addition, the low Q m is not the intrinsic property of PN ceramics, but rather related to the phase transition of silicon oil within pores of ceramics, as indicated by the increase in Q m from 47 to 80 after heat-treatment in air. [ABSTRACT FROM AUTHOR]

In this study, we synthesize pristine and (Mg, Fe) co-doped SnO 2 nanoparticles using the chemical co-precipitation method, where the Mg doping amount is fixed (2 mol%) and the amount of Fe is varied between 2 and 6 mol%. The narrow and sharp natures of intense XRD peaks notify that the crystallinity is pretty well. The formation of the single-phase tetragonal rutile type structure of all prepared compounds has been identified by Rietveld refinement, Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. Moreover, the well incorporation of Fe and Mg in SnO 2 and absence of any other unexpected elements are confirmed by the energy dispersive X-ray spectroscopy. How the co-doping of Mg and Fe alter the crystallite size, microstrain, and dislocation density of the prepared samples have been investigated by Scherrer method with various modified version of it, Williamson-Hall method (W–H) in three factions (UDM, USDM, and UDEDM), Size strain plot (SSP) method, Halder-Wagner (H–W) method, Wagner-Aqua (W-A) method, and Warren-Averbach (WA) method. The obtained crystallite size using the WA method is smaller than the other methods and Scherrer-based methods show much comparable (except SLMSE) sizes. Additionally, the W–H, H–W, SSP, and W-A plots show almost similar tendency of decreasing crystal size, increasing dislocation density and lattice strain with increasing doping. The scanning electron microscopy (SEM) profiles revealed that the synthesized nanoparticles are agglomerated in nature, where the agglomeration increases with decreasing crystal size. The magnetic response of the prepared samples revealed a weak ferromagnetic (or soft magnetic) nature, where saturation magnetization increased due to doping, and a reducing trend of remanent magnetization and coercivity was explored which indicates the phase transition from ferromagnetic to paramagnetic. However, this soft magnetic nature was modified with the influence of defects like changes in lattice parameters, strain, and oxygen vacancy. This phase transition at higher doping concentration makes our nanomaterial as a suitable contender for memory devices, hyperthermia treatment, and photothermal effect. [ABSTRACT FROM AUTHOR]

This study investigates the thermal behavior and structural transitions of silver vanadate microrods (AgVO 3) synthesized via coprecipitation. The samples were characterized at room temperature using scanning electron microscopy, Powder X-ray Diffraction, and Raman scattering. The AgVO 3 was obtained in the monoclinic phase (β-phase) with a Cm space group and rod-like morphology of micrometer-sized diameter. In situ temperature-dependent studies utilizing XRD and Raman spectroscopy revealed notable findings: at low temperatures (298–12 K), the β-AgVO 3 phase exhibited thermal stability alongside uniaxial negative thermal expansion (NTE) along the b lattice parameter of microcrystals. Conversely, experiments at high temperatures (298–673 K) demonstrated a reversible structural transition from the monoclinic phase to a triclinic phase at 473 K (β → β'), with NTE observed along the b direction in both high-temperature phases. These temperature-induced structural modifications and the observed uniaxial negative thermal expansion in β-AgVO 3 microrods constitute significant contributions to the field, providing valuable insights into their thermal behavior and potential applications. • Temperature-dependent behavior of silver vanadate (β-AgVO 3) microrods using in situ XRD and Raman scattering. • β-AgVO 3 microrods present reversible monoclinic to triclinic phase transitions at high temperatures. • The β-AgVO 3 microrods exhibit uniaxial negative thermal expansion along the b-axis at low and high temperatures. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) with a narrow diameter distribution and high areal density hold great promise for a variety of applications, particularly in advanced electronics and biomedical devices. This study utilizes Mn ion doping as a strategic approach both to stabilize the ZrO 2 -supported Fe catalyst and regulate lattice oxygen release, thereby facilitating the growth of SWCNTs with high areal density and a narrow diameter distribution. The ZrO 2 -supported Fe catalyst was meticulously dispersed on Si/SiO 2 (300 nm) substrates through the optimization of spin-coating speed and solvent viscosity, aiming to enhance the dispersion and uniformity. Investigation into the precise control over the Mn ion content was conducted to regulate the structure and stability of the Mn-doped ZrO 2 -supported Fe catalyst. Mn ions perform a dual role: they maintain a higher proportion of ZrO 2 in the monoclinic phase, which in turn alleviates the monoclinic-tetragonal phase transition during chemical vapor deposition (CVD) growth. Concurrently, the conversion of Mn3+ to Mn4+ ions captures the lattice oxygen released during the formation of zirconium transition oxides. Additionally, first-principles simulations have confirmed the stabilizing impact of Mn ions on the catalyst, which reduces aggregation and maturation, ultimately resulting in a more concentrated diameter distribution of as-grown SWCNTs. This approach has successfully achieved the controlled growth of high areal density SWCNTs with a diameter distribution of 1.73 ± 0.08 nm. [Display omitted] [ABSTRACT FROM AUTHOR]

The search for spin-reorientation (SR) phase transitions, a spontaneous rotation of ordered magnetic moments, in ferrimagnetic (FiM) materials, which carry a net magnetization, is of fundamental and practical interest for applications in the field of spintronics. In this work, we have investigated Mn self-doped (Er 0.7 Mn 0.3)MnO 3 solid solution with GdFeO 3 -type Pnma perovskite structure by combining specific heat, magnetic susceptibility and neutron powder diffraction measurements. We provide experimental evidence for FiM order below T C = 104 K, and a spontaneous SR transition at T SR = 11 K. A FiM structure appears in all (R 1-x Mn x)MnO 3 compounds with R = Dy–Lu for x ≥ 0.2. But in this structural family, R = Er is the only material with a SR transition. FiM order in (Er 0.7 Mn 0.3)MnO 3 appears with ferromagnetic (FM) ordering of Mn3+ and Mn4+ cations at the B site along the a -direction, which are antiferromagnetically (AFM) coupled with Er3+ and Mn2+ cations at the A site. At T SR , ordered Er3+ change direction from the magnetically harder a -axis to the magnetically easy b -axis and induce a change of the whole FiM structure, including the direction of all Mn spins from the irreducible representation m GM3+ to m GM4+. We calculated the crystal-field (CF) anisotropy for Ho3+ in (Ho 0.8 Mn 0.2)MnO 3 and Er3+ in (Er 0.7 Mn 0.3)MnO 3 , based on the point charge model; the results revealed large magnetic anisotropies. For the FiM structure of (Ho 0.8 Mn 0.2)MnO 3 , the magnetically easy a -axis of Ho3+ keeps the high-temperature magnetic directions along the a -axis and gives rise to a pronounced magnetization reversal effect at low temperature because of a significant rise of Ho3+ ordered moments. On the other hand, for the FiM structure of (Er 0.7 Mn 0.3)MnO 3 , the magnetically easy b -axis of Er3+ gives rise to a SR phase transition at T SR , which does not lead to magnetization reversal even though Er3+ ordered moments rise significantly at low temperatures. [ABSTRACT FROM AUTHOR]

Phase engineering plays a critical role in enhancing photocatalytic performance of metal oxides. Herein, we demonstrate the phase-selective synthesis of MoO 3 (hexagonal h-MoO 3 , orthorhombic α-MoO 3 , and their junction h/α-MoO 3) through controlled phase transitions by adjusting annealing conditions. As evidenced with photocatalytic hydrogen evolution reaction, h/α-MoO 3 (14.20 μmol/h) phase junction shows superior performance to either h-MoO 3 (9.62 μmol/h) or α-MoO 3 (11.31 μmol/h), with a hydrogen yield of 47.6% and 25.6% greater than that of h-MoO 3 and α-MoO 3 (Pt as cocatalyst), respectively. A systematic study of the chemical structure characterizations, photochemical tests, band structure analysis, and photocatalytic activity evaluation reveal that, the enhancement is attributed to the strong built-in electric field in the h/α-MoO 3 phase junction, which effectively facilitates charge separation. Our findings introduce a novel strategy for improving photocatalytic performance using phase engineering. [Display omitted] • MoO 3 with different phase structures can be synthesized by controllable phase transition for h-MoO 3 to α-MoO 3. • Heterophase h/α-MoO 3 demonstrates enhanced photocatalytic hydrogen production efficiency h-MoO 3 and α-MoO 3. • Phase junction induced built-in electric field can promote charge separation toward improved photocatalysis. [ABSTRACT FROM AUTHOR]

In view of industrial applications requiring high piezoelectric activity, KNN-based ceramics face two key constraints: insufficient density and temperature sensitivity. To address these challenges, this study first introduces BaSnO 3 and employs two-step sintering method (TSS) for fabrication, thereby synthesizing ternary 0.975K 0.5 Na 0.5 NbO 3 -0.025Bi 0.5 K 0.5 TiO 3 - x BaSnO 3 (KNN-1000 x BaSn; x = 0, 0.3 %, 0.6 % and 0.9 %) with superior piezoelectricity (d 33 = 217–257 pC/N; d 33 * = 265–330 pm/V; S = 0.16–0.21 %), high Curie temperature (T C = 325–349 °C) and densification (4.3–4.5 g/cm3; relatively density ∼96 %). In one respect, the TSS allows minimal volatilization of alkali metals while promoting grain homogenization. In another respect, the introduction of BaSnO 3 enhances the mobility of domain walls, meanwhile fosters diffuse phase transitions (DPT) and widens dielectric peaks without significantly impairing T C. Moreover, the KNN–6BaSn obtain not only reinforced d 33 (256 pC/N) with high T C (325 °C) and ε ′ (1016), but also fatigue resistance and extreme-temperature endurance with excellent d 33 * (445 pm/V at 90 °C; 300 pm/V at 180 °C). This work provides a resultful dual-strategy for the emergence of lead-free piezoelectric products. • Upgraded piezoelectricity and high Curie temperature in lead-free ceramics. • Newly-designed two-step sintering technique optimized volatilization and porosity. • Concrete function of BaSnO 3 on defects, relaxation and phase boundary was revealed. • Addition of BaSnO 3 heightened fatigue resistance and extreme-temperature endurance. [ABSTRACT FROM AUTHOR]

Addressing a changing energy environment, sodium-ion batteries (SIBs) have emerged as one of the most potentially applicable energy resources in the world. Nevertheless, its further application is hindered owing to high degree of interfacial degradation and structural changes, which caused rapid capacity fading. Herein, a novel Ce modified P2-type layered structure cathode material Na 0.67 Mn 0.8 Co 0.17 Ce 0.03 O 2 @ CeO 2 is introduced, the stability of cell is improved by simultaneous bulk doping and surface coating in one scalable step. The doping of Ce4+ increases sodium ion transport rate by shrinking transition metal layer ions and expanding Na layer spacing. Irreversible phase transition can be mitigated from the stronger the bond energy between TM and O, which is conducive to the decrease in the Mn3+/Mn4+ ratio, and suppression of the Jahn−Teller distortion. Besides, the doping of larger radius Ce4+ extends the internal paths of crystal structure, which decreases the barrier of Na+, correspondingly, the Na+ diffusion rate was increased. Meanwhile, the CeO 2 coating layer effectively inhibits parasitic reactions on the surface and improves the stability of the interface. Which display excellent capacity with a remarkable retention of 86.9 % after 100 cycles at 0.5 C and outstanding discharge rate performance of 87 mA h g−1 at 20 C. This study provides a simple process to concurrently stabilize the bulk structure and interface for the future application for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

The present study focuses on the effect of molybdenum and nitrogen on the microstructure and mechanical properties of VC x O y -Fe cermets. Samples with 0–23 at% Mo were fabricated using a wet synthesis route and heat treatment under Ar and N 2 atmospheres. Phase transformations during heating were investigated by TGA-DSC in combination with XRD, and the resulting materials were analyzed by SEM/EDX. A doping level of 6–12 at% was found to be optimal, as it lowered the melting point of the metallic binder to 1320–1360 °C. Replacing argon with nitrogen further decreased the melting point to 1210–1240 °C and reduced the grain size. Depending on the sintering temperature, gas environment, and molybdenum content, the produced cermets were characterized by 92–97 % density, 17–29 vol% binder phase, 8–14 GPa hardness, and 6–9 MPa m0.5 fracture toughness. The average size of oxycarbide grains, their stoichiometry, and the amount of dissolved vanadium in the iron binder demonstrated a strong correlation with changes in mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Microchannel condensers play an essential role in cryogenic two-phase heat management systems due to their efficient heat transfer characteristics. Thus, it is worth conducting an in-depth study on microscale condensation characteristics of cryogenic fluids. This paper delves into the flow condensation process of methane in microchannels. A two-dimensional transient model with high accuracy for cryogenic fluids has been developed by combining a self-defined program for the source term of the phase transition model. The model fully considers the boundary layer thickness and accurately explores the mesh accuracy. The complete condensation flow patterns are captured for various vapor quality, mass flux, and wall subcooling degrees. The injection flow is a unique flow regime for condensation in microchannels. The decrease in wall subcooling degree and increase in mass flux leads to the separation point at the neck of the injected flow moving towards the exit, while the annular flow region is expanding and the flow pattern transition is lagging. The mass flux improves the heat transfer coefficient more significantly at high vapor quality. During injection and bubble flow, the wall shear stress and local heat transfer coefficient are subject to bouncing and oscillations, which may induce fluctuations in the upstream annular flow. The prediction performance of six classical heat transfer correlations is evaluated. The results indicate that the Nie et al. correlation has the highest comprehensive prediction accuracy with MRD and MARD of -5.00 % and 15.83 %, respectively. [ABSTRACT FROM AUTHOR]

Pr 2 NiO 4+δ -based materials are considered as promising air electrodes for proton ceramic electrochemical cells due to their wide range of attractive properties. In the present work, the basic functional properties of Pr 2 NiO 4+δ are optimized by substituting Pr-cations with isovalent La- and Nd-ions. The synthesized samples are characterized by X-ray diffraction analysis, thermogravimetry in oxidizing and reducing environments, dilatometry, and four-probe conductivity measurements. As a result, the relationships between crystal and defect structures on the one hand and their electrotransport and thermomechanical properties on the other hand are revealed. The PrLaNiO 4+δ , Pr 1.5 La 0.5 NiO 4+δ , and PrLa 0.5 Nd 0.5 NiO 4+δ compositions are stabilized by the large lanthanum cation and do not show the phase transition (from Fmmm to I 4/ mmm space group) typical of the other studied compounds. The conductivity values of the studied materials remain practically unchanged for most of the compositions, but the La-doping reduces the activation energies of hole transfer. Based on the obtained data, two optimal compositions (Pr 1.5 La 0.5 NiO 4+δ and PrLa 0.5 Nd 0.5 NiO 4+δ) can be identified for their further application in electrochemical cells. [Display omitted] • (Pr x La y Nd z)PrNiO 4+δ (x + y + z = 1) are synthesized by citrate-nitrate method. • Doped materials obtained have orthorhombic structure of Pr 2 NiO 4+δ. • Doping with La or Nd results in a decrease of oxygen content of Pr 2 NiO 4+δ. • Nd- and La-doping have the opposite effect on thermal expansion of Pr 2 NiO 4+δ. • Doping with lanthanum reduces the activation energy of hole mobility. [ABSTRACT FROM AUTHOR]

A new three-step sintering process was presented to produce 0.96(K 0.5 Na 0.5) 0.95 Li 0.05 Nb 0.93 Sb 0.07 O 3 –0.04CaZrO 3 piezoelectric ceramics, this method sets the sintering temperature and holding time for each step based on the traditional solid-state sintering method of the system. Phase structure and polymorphic phase transition temperature were investigated. All of the ceramic samples indicated a perovskite structure, and most of them showed the coexistence of orthogonal and tetragonal phases, according to X-ray diffraction patterns. The dielectric low-temperature spectrum and thermally stimulated depolarization current (TSDC) revealed that the orthogonal-tetragonal phase transition temperature of all ceramics was set below ambient temperature. The crystal structure of the ceramics was changed using the three-step sintering process, which lowered the polycrystalline transformation temperature below room temperature, resulting in excellent piezoelectric properties of the ceramic material. [ABSTRACT FROM AUTHOR]

Mixed lead halide perovskites have shown remarkable performance in photovoltaic and optoelectronic applications. Pure hybrid halide perovskites undergo clear phase transitions, however, the phase transitions in mixed perovskites are less studied. We present a contrasting behavior of the phase transition dynamics of MAPbBr 3- x Cl x (MA = CH 3 NH 3 +) mixed halide perovskites compared to the pure MAPbX 3 (X = Cl, Br) counterparts, which typically exhibit order-disorder phase transitions through a series of distinct structural phases. We have employed several spectroscopic techniques including temperature-dependent PXRD, Raman, dielectric and Brillouin spectroscopy. The results demonstrate that the mixed halide perovskite MAPbBr 1.5 Cl 1.5 does not undergo any structural phase transition typically observed in pure halide perovskites. We observed signatures of glassy behavior in mixed compositions of this system. In addition, we also explored the effects of replacing A-site cation on the phase transition behaviors. The results contribute to the understanding of phase transition mechanisms in perovskites and have implications for their stability and optoelectronic properties. [ABSTRACT FROM AUTHOR]

High-entropy dielectric capacitors have recently drawn increasing attention in the field of energy storage. In this study, NiO has been incorporated into [(Na 0.7 Bi 0.1) 0.8 Sm 0.02 Ca 0.02 Sr 0.02 Ba 0.02 ]Nb 0.8 Sb 0.1 Ta 0.1 O 3 -based ceramics. We applied the concept of high-entropy design to introduce cation vacancies at the A-site, enhancing conformational entropy. This approach led to the successful preparation of a novel type of energy-storage ceramics with an ABO 3 perovskite structure, denoted as (1- x)NBSCSBNST- x NiO (x = 0, 0.02, 0.04, & 0.06). We conducted a systematic study of the microstructural, dielectric, and ferroelectric characteristics, along with an exploration of the influence of the high-entropy strategy on their performance. The Δ S config increases with NiO doping, and the E b of the NBSCSBNST-0.02Ni sample exhibits a significant increase to 730 kV/cm from 550 kV/cm of NBSCSBNSTN. This enhancement is accompanied by a recoverable energy density (W rec) of 4.43 J/cm3 and an efficiency (η) of 75.9 %. As the content of NiO increases from x = 0 to x = 0.06, the phase transition diffusion behavior strengthens. Additionally, the permittivity (ε r) spectrum becomes more uniform, and the activation energy of the prepared ceramic samples increases from 1.03 eV to 1.76 eV. This effect suppresses the emergence of localized electric branching, eventually improving the breakdown strength of NBSCSBNST- x Ni ceramic materials. The obtained results indicate that the concept of high-entropy design to introduce cation vacancies at the A-site is an efficient approach to improve the energy storage characteristics of lead-free dielectric capacitors. [ABSTRACT FROM AUTHOR]

Cr 2 Mo 3 O 12 ceramics show negative thermal expansion (NTE) in a narrow high-temperature range due to the phase transition around 385 °C. To widen its NTE temperature range, a series of (NaMg)3+ co-doped Cr 2 Mo 3 O 12 ceramics has been synthesized via a solid reaction process in this work. The effects of double cation (NaMg)3+ co-doping on the phase composition, morphology, phase transformation, and thermal expansion performance of Cr 2 Mo 3 O 12 ceramics were studied using XRD, Raman, XPS, SEM, and TMA. Results indicate that double cation (NaMg)3+ can partially substitute Cr3+ in Cr 2 Mo 3 O 12 , which causes a phase transition from monoclinic Cr 2 Mo 3 O 12 to hexagonal (NaMg) x Cr 2-x Mo 3 O 12. The single-phase (NaMg) x Cr 2-x Mo 3 O 12 ceramics with hexagonal structure is obtained when x = 0.5. (NaMg)3+ co-doping promotes the growth of grains and the density of hexagonal (NaMg) 0·5 Cr 1·5 Mo 3 O 12 ceramics. (NaMg)3+ co-doping also successfully eliminates the temperature-induced phase transition of Cr 2 Mo 3 O 12 at 385 °C. Hexagonal (NaMg) 0·5 Cr 1·5 Mo 3 O 12 ceramics presents a better NTE with a coefficient of thermal expansion (CTE) of −3.97 × 10−6 °C−1 over a larger temperature range from 30 °C to 700 °C. [ABSTRACT FROM AUTHOR]