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Perovskite functional ceramics have been widely applied for thermal protection owing to their unique physical properties. However, formation of oxygen vacancies under external stimuli usually limits their performance in practical applications. Therefore, the mechanism of the effect of oxygen vacancy on the layer structure of perovskite La0.9Sr0.1TiO3+δ was investigated by experiments and first-principles simulations. The experimental results showed that the lattice distortion occurred in oxygen-deficient environment to give a longer c-axis, along with a significant adjustment in the modes of A/B–O bond vibration, resulting in lower reflectivity. Advanced transmission electron microscopy studies revealed that oxygen vacancies induced localized atomic rearrangements via [TiO6] layer movements to adapt to the lattice distortion. This eventually restructured a part of the layer interfaces by expanding the overlapping projection of atoms in the c-axial direction. The specific transformation process was described as a compendious process, while geometric phase analysis effectively clarified how oxygen vacancies can inhibit reflectivity on the layer structure. Thus, this study provides effective approaches for researching the effects of oxygen vacancy on the physical properties of orthorhombic layer perovskite structures, which may facilitate the development of perovskite-based functional devices.

A glass ceramic from the MgO–Al2O3–SiO2 system containing additives of ZrO2, TiO2, La2O3 and P2O5 was investigated. Via x-ray powder diffraction (XRPD) and Transmission electron microscopy(TEM) the crystalline phases present could be identified as MgAl2O4 (Spinel), orthorhombic ZrTiO4 and a polymorph of LaPO4 with a previously unknown crystal structure. The crystal structure of this LaPO4 phase was solved ab initio via 3D ED Data. The polymorph occurs in a distorted barite structure type in the same space group (P21/n) as the stable monazite type polymorph, however the density is higher and the La has a higher coordination number. Furthermore the LaPO4 is present in a spinodal relict microstructure. Potential explanations for the presence of this metastable polymorph are pressure due to residual stresses from the crystallization or surface effects due to the high surface area resulting from the spinodal relict structure.

Ca-doped Ni–Mg–Mn spinel ferrites with compositions of Ni0·5Mg0·3Mn0.2CaxFe2-xO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared via sol-gel auto-ignition technique. TGA/DTA, FTIR, XRD, FESEM, and VSM were employed to evaluate the thermal, spectral, structural, morphological, and magnetic features of Ca-doped Ni–Mg–Mn spinel ferrites. TGA/DTA curves show the weight loss in the sample. This weight loss was attributed to the oxidation and decomposition of the sample contents at a temperature of 500 °C. XRD reveals a single-phase structure of the Ni–Mg–Mn nano ferrites. A single-phase orthorhombic structure was confirmed for Ca-doped Ni–Mg–Mn ferrites. Structural parameters such as lattice parameter, ‘da’, ‘db’, ‘dc’, and ‘dv’ were evaluated using unit cell software. The absorption peaks at 427 to 538 cm−1 confirmed the spinel structure, which was evaluated using FTIR. FESEM analyses showed that the agglomerations increased with the doping of Ca in Ni–Mg–Mn ferrites. Remanence, Y–K angles, saturation, coercive force, magnetic squareness, magnetic moment, and anisotropy constant were determined for Ca-doped Ni–Mg–Mn spinel ferrite samples. It is noticed that saturation increases from 29.157 to 51.322 emu/g, whereas remanence increased from 5.34 to 9.40 emu/g, respectively. The permeability, anisotropy constant, and magnetic moments were also found to increase with Ca doping. However, the Y–K angles increased with Ca concentration in Ni–Mg–Mn nano ferrites. In addition, the switching field distribution (SFD) and high-frequency response of all the Ca-doped Ni–Mg–Mn samples were also evaluated. Ca-doped Ni–Mg–Mn samples are suggested to be suitable for switching, filters, inductors, and microwave absorption applications because of the superparamagnetic nature of the prepared spinel ferrites.

Li/Ce co-doped BaBi4Ti4O15–Bi4Ti3O12 (BBT-BIT) intergrowth bismuth layer-structured piezoelectric ceramics were prepared by conventional solid-state method. The X-ray diffraction, Raman spectroscopy, and scanning electron microscopy results showed that all the samples had a single orthorhombic phase structure, indicating that Li/Ce dopants had successfully dissolved into the BBT-BIT lattice. Li/Ce co-doping improved the piezoelectric properties of the ceramics: d33 increased from 6.8 pC/N to 21.4 pC/N and the Curie temperature Tc increased from 483 °C to 544 °C. Among all the ceramics investigated, the Ba0.7(Li0.5Ce0.5)0.3Bi8Ti7O27 ceramic showed the best comprehensive properties with d33 = 20.2 pC/N, Tc = 540 °C, tanδ = 0.53%, Ea = 1.13 eV, 2Pr = 10.5 μC/cm2. Meanwhile, the hysteresis loop of the BBT-BIT-0.3(Li0.5Ce0.5) sample sintered in an oxygen atmosphere was asymmetric, which may have been caused by defects produced by the Li/Ce co-doped. Besides, a d33 value of 18.5 pC/N was achieved at 450 °C, which is 91.6% of the value at room temperature, indicating the good thermal stability of the ceramic. The sample showed high resistivity, which can be attributed to the decrease in the concentration of the oxygen vacancies. Our results suggest the great potential of Li/Ce co-doped BBT-BIT intergrowth piezoelectric ceramics for high-temperature applications.

Ca1-xCexBi2Nb1.975(Cu0.25W0.75)0.025O9 (CBNCW-xCe: x = 0.00, 0.02, 0.04, 0.06, and 0.09) lead-free piezoelectric ceramics with improved piezoelectric properties were prepared by the traditional solid-state reaction method. The effects of CeO2 doping on the microstructure and electrical properties were investigated in detail. XRD patterns and Rietveld refinement show that the crystal structures of the samples transform from the orthorhombic phase into the pseudotetragonal phase and that the lattice distortion is weakened. Raman and XPS spectra indicate that Ce ions exist with +3 and + 4 valences in the air sintered ceramics, in which Ce4+ replaces Nb5+, causing the weakened NbO6 octahedral vibration of torsional and tensile and an increase in oxygen vacancies in the doped ceramics. When x = 0.04, it shows excellent comprehensive properties with a high d33 value of 18.1 pC/N, a Tc value of 900 °C, and a ρdc value of 2.8 × 105 Ω cm at 500 °C. Our results suggest that the CBNCW-0.04Ce ceramic is a promising candidate in high-temperature piezoelectric applications.

BaO-Sm2O3–5TiO2 (BST) added by Al2O3 was prepared by solid-state reaction method. The main phase is Ba3.99Sm9.34Ti18O54 of orthorhombic tungsten bronze structure, and the secondary phase is Ba1.18Al1.90Ti6.09O16 of tetragonal structure, which has two types of grains: one is grey and cubic, and the other is white and quasi-rectangular. Microstructure was characterized by XRD, SEM, and Raman spectra. Micromechanical properties of different phases were assessed by nanoindentation and micro-scratch tests with Berkovich indenter. Volume fractions of different phases obtained by statistical analysis of grid indentation are in good agreement with those obtained by XRD analysis. Vickers hardness method is more appropriate for the determination of the fracture toughness of dielectric ceramics. BST ceramic without addition of Al2O3 has better mechanical properties than BST-A with addition of Al2O3, indicating that addition of Al2O3 impairs the micromechanical properties of dielectric ceramics.

MgNb2-xVx/2O6-1.25x (0.1≤x≤0.6) ceramics with orthorhombic columbite structures were prepared at low-temperature by a solid-phase process. The phase component, microscopic morphology, low-temperature sintering mechanism and microwave dielectric performance of MgNb2-xVx/2O6-1.25x ceramics were comprehensively investigated. Low-temperature sintering densification of dielectric ceramics was achieved via the nonstoichiometric substitution of vanadium (V) at the Nb-site. In contrast to pure MgNb2O6 ceramics, the sintering temperature of MgNb2-xVx/2O6-1.25x (x = 0.2) ceramics was reduced by nearly 300 °C owing to the liquid-phase assisted sintering mechanism. The liquid phase arises from the autogenous low-melting-point phase. Meanwhile, MgNb2-xVx/2O6-1.25x (x = 0.2) samples with nonstoichiometric substitution could achieve a more than 900% improvement in the Q × f value, compared with stoichiometrically MgNb2-xVxO6 (x = 0.1, 0.2) ceramics. Finally, MgNb2-xVx/2O6-1.25x dielectric ceramics possess outstanding microwave dielectric properties: er = 20.5, Q × f = 91000, and τf = -65 ppm/°C when sintered at 1030 °C for x = 0.2, which provides an alternative material for LTCC technology and an effective approach for low-temperature sintering of Nb-based microwave dielectric ceramics.

A new type of microwave dielectric ceramics with low dielectric loss was fabricated through a traditional solid-phase method. X-ray diffraction and density tests showed that KSrPO4 ceramics with a single orthorhombic phase could be synthesized and densified at 950 °C, and the crystal structure of KSrPO4 was further confirmed by Rietveld refinement analysis. The densification temperature of KSrPO4 was lower than 961 °C, indicating the ceramics could be used in LTCC devices. Additionally, based on the complex chemical bond theory, some internal parameters of KSrPO4 ceramics were calculated and the effects of these parameters on the properties of KSrPO4 were systematically analyzed for the first time. Furthermore, the composite dielectric constant and loss of KSrPO4 ceramics were analyzed by infrared reflectance spectroscopy, and the theoretical loss and the actual loss were compared. Finally, a vector network analyzer was employed to measure the microwave dielectric properties of all samples. The results showed that KSrPO4 sintered at 950 °C obtain the best microwave dielectric properties, including er = 7.85, Q·f = 34,527 GHz (at 10.43 GHz) and τf = −14.82 ppm/°C.

Current report is based on the synthesis of Gd+3 doped V2O5 nanostructures (GVO) along with fabrication of GVO/MXene binary nanocomposite. As synthesized GVO and GVO/MXene were characterized by XRD (X-ray diffraction), FESEM (Field emission scanning electron microscopy), EDX (Energy dispersive X-ray), BET (Brunauer Emmett Teller technique) and UV–Visible spectroscopy. Diffraction and elemental analysis confirmed the substitution of Gd+3 ions in VO layers. Orthorhombic phase of VO was observed in both GVO and GVO/MXene samples with crystallite size range of 17.02–17.51 nm. FESEM analysis indicated asymmetrical VO particles and sheets distributed on MXene layers, giving out a sponge like appearance. Surface area of GVO and GVO/MXene was enhanced to 20.46 and 23.69 nm, respectively. Effect of Gd+3 contents was significant on optical properties, which reduced the band gap energy of VO to 2.33 eV. The photocatalytic performance of prepared samples was analysed by the degradation of Methylene blue (MB) under direct sunlight. Gd+3 ion doping was found useful to enhance degradation of MB up to ∼71%. Among all samples, GVO/MXene showed maximum degradation (∼92%) within 120 min. Meanwhile, GVO/MXene showed good recyclability for successive five cycles. In addition, GVO and GVO/MXene were effective antibacterial agents against Gram positive (S. aureus) and Gram negative (P. vulgaris) strains of bacteria. The results suggested that the GVO and GVO/MXene could serve as potential candidates for large scale treatment of organic pollutants and pathogens.

A series of high-k Ba4Nd28/3Ti18-yGa4y/3O54 (0≤y≤2, BNTG) ceramics with temperature stable and ultra-low dielectric loss were synthesized via the conventional solid-state reaction. The main phase of all BNTG ceramics demonstrated an orthorhombic tungsten-bronze structure, but the impurity phase (gallium-rich phase) was found in BNTG (y = 2) ceramic. Partial substitution of Ga3+ for Ti4+ in B-site was a valid method to improve the temperature stability and dielectric loss of BNTG ceramics. The variation of er values of BNTG ceramics was dominated by the ionic polarizability. The ultra-low dielectric loss (ultra-high Q × f values) was associated with grain size, suppression of Ti3+ and impurity phase. The decrease of TCF values was highly dependent on the tilting of Ti-O octahedra and impurity phase. Finally, outstanding combination dielectric characteristics were achieved for BNTG microwave ceramics at y = 1.5 (er = 72.8, Q × f = 14,600 GHz, TCF=+4.1 ppm/°C) and at y = 2 (er = 70.3, Q × f = 15,500 GHz, TCF=+3.9 ppm/°C).

Perovskite lattice was tailored by introducing site vacancies and mixed anion composition, to produce Sr0.83Li0.17Ta0.83O1.88N0.74 (Li02N). Further, Li02N was converted to a defect oxide Sr0.83Li0.17Ta0.83O3 (Li02O) by applying an optimized treatment: heating in air at 1173 K for 2 h. According to the neutron Rietveld refinement, Li02N and Li02O are tetragonal and orthorhombic, respectively, where the lattice volume of Li02O is significantly smaller than that of Li02N. The ionic conductivity (σion) of Li02N and Li02O was evaluated by the ac impedance spectroscopy and the equivalent circuit analysis. Both Li02N (σion = 10−5.5 S/cm at 671 K) and Li02O (σion = 10−6.2 S/cm at 667 K) exhibited an Arrhenius behavior of ionic conductivity with activation energies of 0.87 eV and 0.75 eV, respectively. It is interpreted that the nitride component enhances the ionic conduction of Li02N, while the vacancy of the anion lattice makes an opposite effect.

A series of BaBi2-xNb2ErxO9 ceramic compositions with different Er3+ concentration (x = 0.0–8 mol %) is synthesized by a conventional solid-state reaction method. The upconversion (UC) light emission under 980 nm excitation with different pump powers and luminescence-based temperature sensing ability of BaBi2-xNb2ErxO9 composition have been examined. The formation of a Bi-layered perovskite phase of BaBi2Nb2O9 is confirmed having an orthorhombic geometry and Fmmm space group. Shifts in the Raman modes indicate reduced interaction of Bi3+ ions with NbO6 octahedron leading to relaxation of structural distortion with increasing Er3+ content. The maximum value for remnant polarization and coercive field of doped BaBi2-xNb2ErxO9 ceramic for (x = 0.08) Erbium concentration comes out to be 2.9524 μC/cm2 and 49.8980 kV/cm. For an optimum content of x = 0.04, two strong UC green emission bands were observed at 549 nm via 4S3/2 → 4I15/2 transition and 527 nm via 2H11/2 → 4I15/2 transitions, and a weak red emission appears at 657 nm attributed to the 4F9/2 → 4I15/2 transition. Pump power dependence suggests that UC emission is a two-photon mechanism for red and green emission bands. Temperature sensing evaluated by the change in the fluorescence intensity ratio (I527/I549) indicates the highest sensitivity to be 0.00996 K−1 at 483 K for an optimum concentration of Er3+ at x = 0.04 in BaBi2-xNb2ErxO9 composition and is useful for non-contact optical thermometry.

Introduction of artificial pinning centres in different morphology is a beneficial way to improve the flux pinning properties of a YBCO compound. In the present study, we report the effect of addition of sodium niobate (NaNbO3) nanostructures in two different form i.e. nanorods (NRs) and nanoparticles (NPs) with a varied wt% (0, 0.5, and 1 wt%) on the pinning capabilities of bulk YBCO polycrystalline samples. The orthorhombic crystal structure of YBCO was confirmed by the XRD spectra even in the nanocomposite samples. The existence of NPs or NRs on the surface and between the superconducting grains of YBCO was confirmed by morphological analysis. The critical temperature (Tc) remains almost unchanged as compared to pure YBCO on addition of NaNbO3 nanostructure in YBCO compound upto 1 wt% concentration. Even at higher fields (upto 6 T) and higher temperatures (upto 75 K), the addition of NaNbO3 NPs or NRs in YBCO nanocomposite resulted in a significant increase of ~2.6 times in the critical current density as compared to pure YBCO. In comparison to NRs added YBCO nanocomposite samples, NPs added YBCO nanocomposite samples showed higher improvement. Throughout the entire investigated range of applied field, the maximum pinning force was found for 0.5 wt% NPs added composite sample.

This work compares the dielectric properties of two new materials. One was 0.88 bismuth manganite–0.12 lead titanate (noted BM–PT hereafter) ceramics composite obtained by standard high-temperature sintering. The second composite was obtained from powdered ceramics dispersed in epoxy glue (noted BM–PT–epoxy). The occurrence of four phases in the ceramics, using X-ray powder diffraction (XRD), was recognized: orthorhombic Pbam, cubic Pn 3 ‾ m, cubic Pm 3 ‾ m, and monoclinic P2/m phase. Pseudo-Voigt function fitting confirmed significant structural disorder in the BiMn2O5 crystal lattice. Analysis of broadband dielectric spectroscopy data confirmed the applicability of the small polaron model to explain detected relaxation processes. Involvement of oxygen vacancies in relaxation and their correspondence to ordered, uniform potential wells in crystal lattices was deduced. Electric conductivity relaxation times behavior proved the sensitivity of the ceramics’ electrical features to hydrostatic pressure. BM–PT–epoxy composite exhibited dielectric permittivity and losses two orders of magnitude lower than those of BM–PT ceramics that opened new prospects to application. One relaxation process in BM–PT–epoxy composite related to the ceramics fill contribution. Other induced relaxation, observed only in this composite, was attributed to interactions at interfaces between the introduced powdered ceramics and the epoxy glue matrix. We showed that stresses generated either by hydrostatic pressure or through the interfacial interaction of epoxy matrix led to the same results: relaxation times shortening.

In the current report, pure V2O5, a series of Gd doped V2O5 (1 wt%, 3 wt%, 5 wt% and 10 wt%) and graphene integrated Gd–V2O5 photocatalysts have been prepared using a facile wet chemical approach. The effect of Gd+3 ions substitution and RGO support on V2O5 was studied by the different analytical techniques. X-ray diffraction (XRD) results showed the orthorhombic crystal structure of synthesized samples with crystallize size in range of 22–35 nm. Morphological analysis showed nanorods and nanorod arrays like appearance of V2O5, Gd–V2O5 and GdV-2O5/RGO, respectively. Gd–V2O5 and Gd–V2O5/RGO exhibited enhanced optical response in the visible region along with decrease in the band gap values for Gd doped V2O5 samples. BET surface area of Gd–V2O5 and Gd- V2O5/RGO was calculated as 12.39 g/m2 and 15.35 g/m2 that was found to be higher than pristine V2O5. To study the photocatalytic activity of synthesized photocatalysts, methylene blue (MB) was chosen as model pollutant. Among the Gd doped V2O5 samples, highest photocatalytic activity (45.62%) was achieved by optimal concentration of 5 wt% Gd–V2O5 that is accredited to effective separation of electron-hole pairs. While Gd–V2O5/RGO showed 2.1 times higher dye removal (97.12%) than unsupported Gd–V2O5, under the visible light irradiation. The significantly high photocatalytic activity of Gd–V2O5/RGO is due to the synergistic effect aroused by combined action of Gd+3 ions doping and advantageous properties of highly conductive and large surfaced graphene. Recycling experiments for V2O5 derivatives showed good stability and recyclability of photocatalysts. Additionally, Gd–V2O5/RGO was found to be more potential anti-bacterial agent than V2O5 and Gd–V2O5.

Europium doped (0.1% and 1%) chloroborate BaO–B2O3–BaCl2 glass and glass-ceramic with embedded BaCl2 nanocrystals have been synthesised, investigated, and compared with the corresponding nanocrystalline powder. The structural analysis of the glass evidenced ionic bonds characteristic to the glass host structure and compositional changes during the melting. X-ray diffraction and transmission electron microscopy revealed the formation of orthorhombic BaCl2 nanocrystals of about tens on nm in size and a smaller amount of BaB2O4 nanocrystals. Structural analysis of the Eu2+-doped BaCl2 nanocrystals has shown a distortion of the crystalline cell assigned to the growth process, affected by defects and ionic impurities. Photoluminescence spectra of the glass-ceramic revealed Eu3+ and Eu2+ luminescent ion species, but only Eu2+ is incorporated within the BaCl2 nanocrystalline phase. Electron paramagnetic resonance measurements in X-band sustain the presence of Eu2+ ions. The EPR parameters (g values and hyperfine constants) resulting from the Q-band EPR spectra simulations recorded on glass-ceramic are similar to those in Eu2+-doped BaCl2 and confirmed the partial incorporation of Eu2+ ions within the BaCl2:Eu2+ nanocrystals in the glass-ceramics.

The moisture resistance of 5 mol% Nd2BaCuO5-added Nd1+xBa2−xCu3Oy (x = 0–0.8) ceramics was investigated. The samples were prepared by a solid-state reaction at 980 °C and exposed to a humid atmosphere at 40 °C and 93 %RH. The microstructure observation and X-ray diffraction measurement of the exposed samples revealed that the surface morphology and the crystal structure tended to be more stable when the amount of x was increased. The crystal structure was orthorhombic for x = 0 and tetragonal for x = 0.2–0.8. By comparing the lattice constants calculated by the bond valence to those determined by X-ray diffraction, it was suggested that a gap around the Ba site increased with the increasing x. The gap around the substituted Nd3+ for Ba2+ was considered to act as a trap site for OH−.

Due to the similarity in composition and crystal structure of some TiAlSi ternary intermetallics, it is quite difficult to accurately confirm their physic characteristics, and thus, to tailor microstructure to improve mechanical properties of metal materials related to the TiAlSi intermetallics. Therefore, the formation process of TiAlSi intermetallics was investigated during heating Ti-A356 mixed powder compact at a A356 alloy semisolid temperature of 595 °C. The results indicated that two kinds of intermetallics of τ1 (tetragonal, I41/amd) and τ2 (orthorhombic, Cmcm) generated, and both the concentration and supply direction of Ti atoms, which are related to local breakage of oxide films on neighboring Ti and A356 alloy powders, determined the phase and morphology of the intermetallics. τ1 and τ2 crystals all had an intrinsic plate morphology, but τ2 crystals were thinner due to more anisotropic growth resulted from their high density of stacking faults (SFs). τ1 lamellar domains generated during growth of τ2 crystals, which were accompanied by decrease in density of SFs. The combined effect of size difference and internal energy difference between τ1 and τ2 crystals made large τ1 crystals coarsen at the expense of τ2 crystals in Ostwald ripening, leading them to finally evolve into an agglomerate of large τ1 plates.

GaN1−xZnOx solid solution has emerged as a promising candidate to generate clean and sustainable hydrogen energy. We revisit the electronic structure properties of ZnO-GaN systems using an evolutionary algorithm designed for crystal structure prediction coupled with ab initio calculations. An orthorhombic GaN-ZnO crystal phase, with space group Pmc21 (no. 26), was uncovered. The thermodynamic stability analysis reveals that while the Pmc21 crystal is not stable against phase separation, GaN-ZnO has low formation enthalpy of ~30 meV/atom and a relatively moderate miscibility temperature of ~461°C. The calculated phonon structure shows that GaZnNO is dynamically stable. The derived direct bandgap (Γ→Γ) value of 1.875 eV could be exploited in solar cell applications, providing high efficiency of ~25% for a thickness of ~0.5 μm based on the metric of spectroscopic limited maximum efficiency. The valence band maximum at the Γ point shows strong antibonding Zn(d)-N(p) character. The Zn(d)-N(p) repulsion mechanism reduces the direct band by almost ~2 eV. Moreover, we find a huge optical bandgap bowing of 6.3 eV. Our calculations indicate that atomic displacements induce dynamical charges of large amplitude and are the key factors favoring strong bandgap variation and extreme bandgap bowing parameters.

Acta crystallographica / B 77(6), 986 - 995 (2021). doi:10.1107/S2052520621010088, A new six-membered cyclic alkanolamine with chemical formula C$_6$H$_{15}$N$_3$O$_3$ was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitro��gen atoms with three hy��droxy��methyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and $^1$H/$^{13}$C/$^{15}$N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit-cell parameters a = 12.1054 (2) ��, b = 13.5537 (2) �� and c = 5.20741 (8) ��. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior., Published by Wiley-Blackwell, Oxford [u.a.]

Different phases of tungsten trioxide (WO3) nanoparticles were synthesised by hydrothermal method involving the extracts of avverhoea bilimbi, citrus limon and tamarindus indica as capping agents. These synthesized nanomaterials were characterized through X-ray diffraction, Raman spectra, Transmission electron micrographs, diffuse reflectance spectra and photoluminescence spectral techniques. The X-ray diffraction patterns and Raman spectra corroborate the formation of different crystal phases viz., monoclinic (m-WO3), orthorhombic (o-WO3) and hexagonal (h-WO3). The morphological and topographical studies were acquired from SEM and TEM images. The surface parameters were examined from BET isotherms. The absorption spectra reveal that the optical band gap energy is found to be higher for h-WO3. The adsorption of Cu(II) ions were found to be effective provided with optimum conditions and the adsorption capacity was found to be 174.5 mgg−1 by the h-WO3 nanoparticles. A study on Langmuir, Freundlich, D–R and Temkin isotherm models, deviation in D–R model implies that the adsorption is chemisorption process and follows pseudo-second order kinetics. The adsorption process is found to be spontaneous and exothermic from the thermodynamic parameters.

High-purity and fine CrB powders are firstly synthesized from Cr and B powders in (Na, K)Cl molten salt at 850 °C for 2 h. Then the as-achieved CrB powders are used as precursors to synthesize homogeneous and size-controlled Cr2AlB2 powders in (Na, K)Cl molten salt at 900 °C for 2 h. Additionally, the formation mechanisms of CrB and Cr2AlB2 in (Na, K)Cl molten salt are also investigated. Results show that the Cr atom, formed by disproportionation of Cr2+ ions in molten salt, reacts in-situ with B powders to form CrB. For the formation of Cr2AlB2, Al and CrB migrate mutually and assemble firstly in the molten salt, and then Al intercalates into CrB to generate Cr2AlB2.

Optimization of materials exhibiting high-temperature superconductivity for producing controllable nano-devices is crucial for industrial applications. Herein we report a comprehensive study of the diffusion process between YBa2Cu3O7−δ (YBCO) and iron particles. Fe diffusion into the YBCO matrix could be fundamental for multilayer systems with YBCO/Fe-alloy interfaces. We have found that the orthorhombic YBCO structure adopts to 3 wt% Fe, while for higher Fe content, a formation of BaFeO3−δ and iron oxides was observed. Complementary measurements confirmed the strong superconductivity suppression in YBCO-Fe materials containing more than 7 wt% Fe. The YBCO with diffused Fe material retain the unit cell orthorhombicity (max. 3 wt% Fe), and their superconducting properties follow the principle of critical scaling with different exponents (γ). The critical current density (Jc), pinning fields (HP) exhibit γ = 1, the first critical field (Hc1) shows γ = 1/2, and critical temperature (Tc) demonstrates γ = 7/4.

A series of lead-free (K0·49Na0·49Li0.02) (Nb0·8Ta0.2)O3 (KNLNT) piezoelectric ceramics modified by CaZrO3 (denoted as KNLNT-xCaZrO3, x = 0–0.05) were synthesized using a conventional solid-state approach. Herein, the influence of CaZrO3 doping on the crystal structure, ferroelectric properties, dielectric properties as well as piezoelectric properties were systematically investigated. The XRD analysis shows that all the proposed samples present pure perovskite phase, revealing the phase structure transition from an orthorhombic to a pseudocubic phase at a threshold value of x is 0.01 and 0.03. Moreover, the in-situ XRD characterization was applied to investigate the transformation process of phase structure: the pseudocubic-tetragonal (TP-T) phase transition temperature has been decreased to room temperature at x = 0.04. In addition, the results were further confirmed by the temperature-dependent dielectric properties. For the microstructure, the typical strip-like domains and nanoscale domains can be found in transmission electron microscopy (TEM) images. Due to the coexistence of orthorhombic and pseudocubic with x = 0.03, the remnant polarization has an anomaly, and large strain value and large signal d33* value is obtained under a 20 kV/cm electric field, which is about 0.106% and 532 pm/V.

LiCoPO4 is an attractive cathode material, but it undergoes poor electronic conductivity and electrochemical performance. This performance is enhanced by substituting iron antisite Cobalt to reduce the direct interaction between the cathode and the electrolyte. Thus, LiCoPO4 doped with Fe was synthesized by the microwave-assisted solvothermal route at 220 °C. According to X-ray diffraction analysis, a single orthorhombic Pn21a phase (a = 10.02 A, b = 6.71 A and c = 4.96 A) was obtained, which transited to Pnma phase (a = 10.21 A b = 5.92 A and c = 4.76 A) after annealing at 700 °C in air. The morphology and particle size of the sample changed after annealing, as shown by TEM. The electrochemical cycling of an annealed sample showed the initial discharge capacity of 125mAh g−1 compared to 12 mAh g−1 for the non-annealed sample, which can be regarded as a partial coating by FePO4 as obtained from X-ray absorption spectroscopy analysis.

In this work, Li2Mg2[WxMo(1−x)O4]3 (i.e., 0 ≤ x ≤ 1) ceramics with high Q×f values were successfully fabricated at low temperatures (i.e., ≤ 950°C). The sintered specimens were found to exhibit of a single orthorhombic phase when x ≤ 0.6, whereas a secondary phase of MgWO4 was detected in the specimens when x ≥ 0.8. The ceramic samples exhibited homogenous microstructures and relatively high densities (i.e., > 90%) . In the sample with x = 0.2, outstanding microwave dielectric properties of er = 8.05, Q×f = 50,780 GHz, and τf = −73.6 ppm/°C were achieved at the sintering temperature of 825°C. Furthermore, no apparent reaction between a Ag electrode and the ceramic matrix was observed during the sintering process. As a result, Li2Mg2[WxMo(1−x)O4]3 ceramics proved to be promising candidate materials for low temperature co-fired ceramic (LTCC) technology.

0.675BiFeO3-0.3BaTiO3-0.025LaFeO3-x mol% Nb2O5 (x = 0–1.25) multiferroic lead- free ceramics, fabricated by conventional solid-state reaction, were studied to reveal the effects of Nb2O5 on the structural, morphology, dielectric, ferroelectric, magnetic and magnetoelectric properties of the BiFeO3-based ceramics. After the addition of Nb2O5, the crystal structure of as-prepared samples remained orthorhombic phase. The doping Nb5+ ion could be able to inhibit grain growth remarkably and suppress the creation of oxygen vacancies of this ceramics, which resulted in the improvement of electrical insulation by two orders of magnitude. The ferromagnetism was apparently enhanced with increasing content of Nb2O5, and the observed remanent magnetization Mr peaked at 0.022 emu/g for x = 1. Suitable amount of Nb2O5 could be beneficial to the dielectric properties, with the optimal x at 0.75, with dielectric constant er of 918 at 100 Hz. The observed magnetoelectric coefficient αME suggested the existence of magnetoelectric coupling effect in these ceramics. The αME value almost decreased after adding Nb2O5, possibly due to the obvious degradation of ferroelectric behaviors.

We present a study on the structural and phonon properties of cobalt-doped orthorhombic molybdenum trioxide (α-MoO3:xCo) hierarchical microrods. The samples were synthesized by solid-state reaction with molar concentrations of 0%, 1%, 3%, and, 5% cobalt. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and Fourier transformed infrared spectroscopy (FTIR) were used to confirm the orthorhombic phase and the structural properties of each sample. The infrared and Raman spectra of the samples show that doping alters the ratio of relative intensities, linewidth, and the shift of the wavenumber of the modes, and a correlation is established between the stretching force constant and wavenumber. Experimental temperature-dependent Raman scattering studies were performed on samples of α-MoO3:xCo over a temperature range of 298–813 K. The Raman spectra showed a phase transition at around 373 K to a self-similar structure, indicating a possible isostructural phase transition (IPT) for samples with 0% and 1% cobalt, a phenomenon rarely reported in the literature. Nevertheless, this phase transition was not observed for samples containing 3% and 5% cobalt, indicating an increase in material stability.

K0.5Na0.5NbO3 (KNN) particles were prepared by a solid–state method. X–ray diffraction, scanning electron microscopy, UV–visible spectrophotometry, and electrochemical impedance spectroscopy were used to study the structure, morphology, and properties of the samples. The obtained KNN is a ferroelectric material with orthorhombic perovskite structure at room temperature. The KNN particles can be used as piezo/photo–bicatalysts for degrading organic pollutants by utilizing vibrational and solar energy; the catalytic activity of the particles can be significantly improved owing to their polarization under an applied electric field. Poled KNN particles show a bicatalytic degradation ratio of rhodamine B (RhB) dye reaching 92% after 60 min. The results indicate that the KNN particles can be applied as attractive ferroelectric catalysts for organic pollutant degradation.

The volatization of cesium at high temperatures makes its immobilization challenging to the nuclear scientists. Present work reports the feasibility of cesium incorporation into an orthorhombic langbeinite phosphosilicate. The structural flexibility, leachability and thermal expansion of K2-xCsxZr2P2SiO12 (x = 0, 0.5, 1.0, 1.5, 2.0) have been investigated. Powder X-ray results authenticates the accommodation of cesium into a single phasic orthorhombic langbeinite structure up to 29.17 wt %. Morphological study reveals the particle agglomeration and poor crystallinity, and vibrational spectral analysis shows peak broadening and peak shift upon increasing the cesium concentration. The static leach test has been performed on the pellet sample and the normalized leaching of Cs is found to be in the order of 101 g/m2. The average coefficient of thermal expansion for K0.5Cs1.5Zr2P2SiO12 is registered as 7.45 × 10−6/K between 303 and 873 K. Cesium insertion into K2Zr2P2SiO12 displays a large deviation in thermal expansion due to the size effect as observed by several researchers for other phosphate and phosphosilicate members.

A novel Li3Mg4NbO8 compound was fabricated through the process of solid-state reaction. The crystal structure, sinterability and microwave dielectric properties of the Li3Mg4NbO8 ceramics were investigated. XRD refinement and Raman spectra results ascertained that the Li3Mg4NbO8 compound crystallized into an orthorhombic Li3Mg2NbO6-like structure with space group Fddd. The er value was strongly impacted by the relative density and average ionic polarization. The Q × f value was mainly affected by the relative density and average grain size. The Li3Mg4NbO8 ceramics sintered at 1150 ℃ showed outstanding microwave dielectric performance: er = 13.8 ± 0.14, Q × f = 103 400 ± 3500 GHz (at 9.6 GHz), τf = −36.0 ± 1 ppm/℃. Additionally, the bond characteristics were calculated for a better understanding of the structure-property correlation for Li3Mg4NbO8 ceramics.

The structure of a binuclear niobium(IV) thiocyanate complex (Bu4N)4[Nb2(μ2-S2)2(NCS)8]·H2O (1·H2O) is studied by X-ray crystallography. Compound 1·H2O crystallizes in the orthorhombic crystal system (space group Pbca) with unit cell parameters a = 23.2139(4) A, b = 25.2962(4) A, с = 32.5478(6) A, V = 19112.8(6) A3, R = 0.0592. The electronic structures of (Bu4N)4[Nb2(μ2-S2)2(NCS)8] and (Bu4N)4[Nb2(μ2-Se2)2(NCS)8] complexes are investigated by X-ray spectroscopy techniques and compared with the structures of polymeric chalcogenides Nb2S4Br4 and Nb2Se4Br4. By XPS it is shown that effective charges on atoms of the {Nb2(μ-Q2)2}4+ (Q = S, Se) core do not change when passing from Br– to NCS– ligands. The HOMO and LUMO structures of (Bu4N)4[Nb2(μ2-S2)2(NCS)8] and (Bu4N)4[Nb2(μ2-Se2)2(NCS)8] are analyzed by XPS and XANES techniques. The largest contributions of S 3p states of NCS– ligands to the occupied molecular orbitals are found to be near the upper boundary of the valence band while the contributions from dichalcogenide bridging ligands have a more uniform distribution. For the conduction band, the contributions of S 3p states of NCS– ligands are located deeper whereas the contributions from dichalcogenide bridging ligands are near the lower boundary of the conduction band. The interaction of Nb 4d and S 3p/Se 4p states of dichalcogenide bridges for the HOMO has an antibonding character, which is bonding for all the other occupied molecular orbitals and antibonding for all unoccupied molecular orbitals.

The crystal and electronic structure properties of Ni-B (nickel-boron) alloy coatings produced by an electrodeposition method have been investigated. The crystal structures of the alloy coatings were determined by x-ray diffraction patterns and supported by extended x-ray absorption fine structure (EXAFS) spectroscopy. The local atomic structure around the Ni atom was obtained from EXAFS studies at the Ni K-edge, and the EXAFS data were fitted with theoretical calculations. With the addition of boron atoms in the nickel environment, NiB composite alloys were formed in the crystals with an orthorhombic "Cmcm" structure. The analysis revealed a limited effect of boron doping in the electronic structure of the nickel atoms. Boron atoms were determined as sitting between the Ni atoms and causing a disturbance in the crystal structure due to providing inhomogeneous interstitial potential and defects.

Eleven examples of hexagonal and orthorhombic polymorphs of intermetallic compounds having 5:3 stoichiometry are listed in the International Crystal Structure Database. A transition temperature between them has only been determined for the Yb–Sb and Sr–Bi systems, but results on the Sr–Bi system are discrepant with those on the Yb–Sb system, in which the phase relationships are well constrained by experimental data, for example, that the lower-temperature polymorph is the prototype orthorhombic Yb5Sb3 structure (αY5Sb3) and the higher temperature polymorph (βYb5Sb3) is isostructural with hexagonal Mn5Si3, with the transformation occurring at 1280 °C. In contrast, thermodynamic modeling on the Sr–Bi system give the inverse sequence of polymorphs with increasing temperature. It appears unlikely that the hexagonal Mn5Si3 structure type can be stable at higher temperatures than the orthorhombic Yb5Sb3 structure in one system, while orthorhombic Yb5Sb3 structure is the stable phase at higher temperatures in another system. The discrepancy can be attributed to the limited experimental data used to model the phase relationships in the Sr–Bi system.

An X-ray diffraction study aimed at establishing the subtle details of the electron density and anharmonicity of the atomic vibrations in a stoichiometric monodomain single crystal of potassium niobate, KNbO3, has been conducted at room temperature (orthorhombic ferroelectric phase Amm2). The cation and anion displacements obtained from the experiment are weakly anharmonic without any manifestation of structural disorder. The chemical bond and interatomic interactions inside and between crystal substructures at the balance of intracrystalline forces are characterized in detail. The role of each of the ions in the formation of the ferroelectric phase was studied and the features of the electron-density deformation in the niobium and oxygen substructures, and the role of each of them in the occurrence of spontaneous polarization are established. The position-space distribution of electrostatic and quantum forces in KNbO3 is restored. It is emphasized that for the completeness of the analysis of the nature of the ferroelectric properties it is necessary to consider both static and kinetic electronic factors, which are of a quantum origin. The experimental results and theoretical estimations by the Kohn–Sham calculation with periodic boundary conditions are in reasonable agreement, thus indicating the physical significance of the findings of this study.

A new pyrophosphate(V) of the formula Co5Cr2(P2O7)4 was obtained in the system Co2P2O7–Cr4(P2O7)3 as a result of solid-state reactions taking place between different reactants. The new compound crystallizes in the orthorhombic system and belongs to the family of pyrophosphates of the general formula M52+M23+(P2O7)4 and is probably isostructural with Fe52+Fe23+(P2O7)4. Powder diffraction pattern, infrared spectrum and SEM image of the new compound were presented. As a new potential inorganic pigment, Co5Cr2(P2O7)4 was tested for its thermal stability, particle size distribution and colour properties, which were studied both for powder and after introduction into organic matrix and leadless ceramic glaze. The colour of Co5Cr2(P2O7)4 powder was defined as deep grey with the colour coordinates L*/a*/b* = 60.63/-1.42/-3.41 and according to the hue angle (h° = 247.39°) it belongs to the blue region. Co5Cr2(P2O7)4, with its relatively high thermal stability (t m = 1230 ± 10 °C) and appropriate colour properties, is a good candidate to be used as inorganic pigment for colouring of acrylic paints. In the case of leadless glaze, the obtained compound acts as a dye.

This paper deals with the study of the physical properties of ZnO/ZnNb2O6/Nb2O5 composite. X-ray diffraction (XRD) proves the coexistence of hexagonal ZnO, tetragonal Nb2O5 and orthorhombic ZnNb2O6. Scanning electron microscopy (SEM) observations reveals heterogenic distribution of grains with average size of about 456 nm. The dielectric measurements are performed in 20 Hz–1MHz frequency range between 150 °C and 350 °C. Theoretical fit demonstrates that the electric resistivity, associated to grains and grain boundaries, decreases as a function of temperature up to 275 °C. At 275 °C, the composite presents a semiconductor-metal transition, confirmed by the temperature-dependence of DC conductivity. Moreover, the AC conductivity variations suggest that the AC conduction mechanisms are explained by the Quantum-Mechanical Tunneling (QMT) model below 275 °C and the Non-Overlapping Small Polaron Tunneling (NSPT) one above 275 °C. Also, the activation energies, related to dielectric relaxation processes and DC conductivity, are almost equal: Ea ~ 0.53eV in the interval 150 °C 275 °C. Moreover, the permittivity variations show the existence of interfacial Maxwell-Wagner-Sillars (MWS) and dipolar polarization.

Fayalite Fe2SiO4 is synthesized by the solid-state reaction without ball milling. The obtained powder is further structurally and electrochemically examined. Field emission scanning electron microscopy (FESEM) showed that microsized powder is obtained. X-ray powder diffraction (XRD) pattern is used for both phase identification and crystal structure Rietveld refinement. The structure is refined in the orthorhombic Pbnm space group. Mössbauer spectroscopy revealed traces of Fe3+ impurity. The bond valence mapping method is applied for the first time on Fe2SiO4 framework. It shows isolated, non-connected isosurfaces of constant E(Li), which further supports the assumptions of the conversion reactions. Electrochemical performances are investigated through galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Ex-situ XRD and Fourier transform infrared spectroscopy (FTIR) analyses are combined to monitor phase change after galvanostatic cycling and to reveal the working mechanism during electrochemical lithiation. This is the peer-reviewed version of the article: Jugović, Dragana, Milović, Miloš, Ivanovski, Valentin N., Škapin, Srečo, Barudžija, Tanja, Mitrić, Miodrag, "Microsized fayalite Fe2SiO4 as anode material: the structure, electrochemical properties and working mechanism" in Journal of Electroceramics (2021), [https://doi.org/10.1007/s10832-021-00260-9]

Tin monosulfide can be grown in cubic (pi-SnS) and orthorhombic (alpha-SnS) polymorphs by low-temperature atomic layer deposition (ALD). The optical properties of these polymorphs make them attractive for the realization of plasmonic solar cells with ultrathin absorber layers down to 10 nm in thickness. SnS is also an earth-abundant and nontoxic compound semiconductor of high interest for regular thin-film photovoltaics. To better understand the behavior of the two SnS polymorphs in ultrathin solar cell configurations, we here fabricate, characterize, and analyze a range of such devices. ALD is used to grow SnS and form heterojunctions with zinc oxysulfide [Zn(O,S)], acting as a buffer layer with a composition-tunable bandgap. Apart from the roles of the SnS polymorph and Zn(O,S) composition, the effects of the back contact material and thicknesses of buffer and absorber layers are investigated. Devices using pi-SnS and pure ZnO buffers yield the highest photocurrents (3.1 mA/cm(2)) and higher open circuit voltage (159 mV) than similar alpha-SnS-based devices. Analysis of the equivalent-circuit parameters suggests that interface recombination limits the voltage for these devices. While Zn(O,S) with a higher sulfur content provides chemical passivation of the SnS interface and excessive open circuit voltages above 600 mV, it also exhibits a too high conduction band offset, which hampers current collection. A growth delay during the ALD of Zn(O,S) on SnS initially amplifies the known sulfur-oxygen exchange reaction, such that a sulfur-rich Zn(O,S) region forms next to the SnS interface. This causes a thin ZnS-like barrier to form already for low cycle fractions of the H2S precursor in the ALD super-cycle. Voltage and fill factor trends suggest an optimal SnS absorber layer thickness in the range of 15-35 nm, presenting an opportunity for plasmonic absorption enhancement. Devices with pi-SnS show most promise, but interface recombination versus current-blocking is a dilemma for the SnS/Zn(O,S) heterojunction.

Lead-free antiferroelectric (AFE) materials have seen a surge of research activity in environmentally friendly energy storage technologies. Recently, considerable work has been done to improve the stability of AFE in NaNbO3 (NN) ceramics, but it remains a grand challenge to obtain typical AFE characteristic double P-E loops in NN ceramics at ambient conditions. In a preliminary estimate of tolerance factor versus average electronegativity difference, we reported the stable AFE phase in 0.95NaNbO3-0.05BiMg2/3Ta1/3O3 sample. The orthorhombic Q to P phase transition was verified by XRD and TEM. Then, the remarkable double P-E loops were obtained in 0.95NaNbO3-0.05BiMg2/3Ta1/3O3 ceramics. Furthermore, a phenomenological model was proposed to explain the P-E relationships and our results. Compared with other reported compounds, the TP-R decreased more obviously from 350 °C to 200 °C. Superior temperature stability (variations of maximum current, current density, and power density within 15% over 30–140 °C) and field induced phase transition were also confirmed by the pulse charge testing. Our work develops a new road for achieving room-temperature double P-E loops in NN ceramics by BiM1M2O3 (M1 might be Mg, Zn, etc; M2 might be Nb, Ta, etc) additives.

In this work, Lu7O6F9 microcrystals with various novel morphologies, including hand broom-like nanorods, nanoparticles, hexagons, spindle-like nanoparticle aggregates, hexagonal prisms and microrods, were prepared via ionic liquid-assisted two-phase method and following calcination approach. Ionic liquid was used as F− resource, morphology controller and two-phase solvent. The effect of preparation condition on the phases and morphologies of the precursors as well as the calcined products was studied in detail. The crystallographic structure of Lu7O6F9 was also confirmed by the down-conversion (DC) spectra of Lu7O6F9: Eu3+ phosphor with Eu3+ ion as the structure probe. Besides, different concentration of Yb3+ ions were introduced to the host to obtain Lu7O6F9: Yb3+, Er3+ phosphors, in case of subsequent investigation on the up-conversion (UC) luminescence properties, UC mechanism and followed temperature sensing behavior. Color-tunable UC emissions were realized and the mechanism was discussed. Furthermore, the optical temperature sensing behavior of orthorhombic Vernier lutecium oxyfluoride was investigated for the first time. The influence of Yb3+ content on the sensing sensitivity was also elaborated. These results imply that the as-prepared Lu7O6F9: Yb3+, Er3+ phosphors could be considered as candidates in color-tunable displaying and optical thermometers.

This article investigates the impact of carbon nanotubes (CNTs) addition on the morphological, structural, magnetic, and electrical transport properties of the YBa2Cu3O7-δ (noted YBCO) bulk system. Samples were synthesized using the solid-state reaction where the added amount of is ranging from 0.0 to 1.0 wt% of the total mass of the sample. All prepared samples were analyzed by powder X-ray diffraction (XRD) technique, scanning electron microscopy (SEM) observations, and physical property measurement system (PPMS). The structural examination via the XRD technique showed that CNTs did not affect the YBCO orthorhombic structure, but it resulted in a variation of the lattice strain. SEM observations showed a fine distribution of nanosized entities of CNTs on YBCO grains and bristles of CNTs branching out, to some extent, at the grain boundaries. The density of nanosized entities of CNTs was intensified at high concentrations. The results of electrical resistivity measurements showed that CNTs have an impact on the critical temperatures of samples. The superconducting critical temperature, Tco, is slightly increased from 91.4 K in the pure sample to 91.7 K in 0.1 wt% CNTs added (S01) sample and abruptly decreased to 82.0 K for high CNTs content. The microscopic nature of samples was then examined by pseudo-gap analysis derived from excess conductivity. The critical current density ( J c m ) as well as the blocking force ( F b ) were deduced from measurements of magnetization versus applied magnetic field. Both J c m and F B were improved drastically by the addition of a small amount of CNTs. J c m increased from 0.3 × 10 4 A . c m − 2 in the pure sample to 1.3 × 10 4 A . c m − 2 in CNTs added sample. This is mainly ascribed to the active contribution of CNTs in increasing the blocking centers in the YBCO system.

A novel decavanadate salt Mg(H2O)6(C6H14N2)2V10O28·8H2O is obtained by the reaction of vanadium oxide and 1,4-diazabicyclo [2.2.2] octane (DABCO). The title compound is characterized by infrared (IR) spectroscopy and powder X-ray diffraction (XRD). The spectroscopic characterization confirms the presence of the different groups in the structure. Powder XRD confirms the purity of the phase. Optical properties are recorded at room temperature using UV-Visible spectroscopy in the spectral range of 250-800 nm. According to the single crystal XRD analysis, the structure of the compound is orthorhombic: a = 17.927(6) A, b = 15.798(6) A, c = 15.723(5) A, V = 4452.8(7) A3, and Z = 4. The formula unit of Mg(H2O)6(C6H14N2)2V10O288H2O is formed by a decavanadate group, the $$\text{Mg(}{{\text{H}}_{2}}\text{O)}_{6}^{2+}$$ polyhedron, two organic (C6H14N2)2+ cations, and eight water molecules. In the crystal, molecules are linked by O–H…O and N–H…O hydrogen bonds, forming a three-dimensional network.

In this work, La-substituted CaBi4Ti4O15 Aurivillius phase, CaBi4-xLaxTi4O15 (x = 0, 0.5, 1, 1.5, and 2), were synthesized by a molten salt method. The effects of La3+ substitution on structure, morphology, dielectric and optical properties were systematically investigated. Refinement of XRD data confirm that a ferroelectric orthorhombic structure with space group A21am was adopted for x = 0, 0.5, 1, and 1.5. In terms of x = 2, the structure transformed to an intermediate paraelectric orthorhombic structure of the Amam space group. The anisotropic plate-like grains were observed across all the samples, which decreased in size with an increase in La3+ content. With La3+ substitution, the ferroelectric transition temperature (Tc) significantly decreased since the structural distortion as the effect of 6s2 lone pair electron of Bi3+ was reduced with the substitution of La3+. Additionally, the reduced structural distortion was responsible for a decrease in the bandgap (Eg) energy. A diffused phase transition of ferroelectric characterized by the broadened Tc peak was induced by La3+ substitution since the increased disorder of A-site cation (Ca/Bi/La). The ferroelectric phase with a lower Tc and the lower Eg energy proposes the sample of x = 1.5 as a potential material for electrocaloric and solar cell applications.

Y$_{0.9}$Gd$_{0.1}$Fe$_{2}$, which crystallizes in a C15 cubic structure, can absorb up to 5 H/f.u. and its pressure-composition isotherm displays a multiplateau behavior related to the existence of several hydrides with different crystal structures. At room temperature Y$_{0.9}$Gd$_{0.1}$Fe$_{2}$H$_{x}$ hydrides (2.9 $\le$ x $\le$ 5) crystallize in three phases with cubic structure (C1, C2 and C3), two phases with monoclinic structures (M1 and M2), and one phase with orthorhombic structure (O), with the following sequence for increasing H concentration: C1, M1, C2, M2, C3, O. Each phase exists as single phase within a H homogeneity range, and they are separated from each other by two-phase domains. The reductions of crystal symmetry are related to various hydrogen orders into interstitial sites. Weak superstructure peaks were indexed by doubling the cubic cell parameter of the cubic C2 phase. Upon heating, the monoclinic M1 and M2 and the cubic C2 phases undergo order-disorder (O-D) transitions toward a disordered cubic structure CDis. These O-D transitions are reversible with thermal hysteresis effects. The cubic C3 and orthorhombic O phases transform into a disordered cubic phase accompanied by H desorption., 16 pages, 8 figures, 2 tables

The pressure-induced structural phase transitions in bismuth tungstate Bi2WO6 have been studied using neutron diffraction and Raman spectroscopy at high pressures up to 7 and 30 GPa, respectively. A rich structural polymorphism was revealed. At P ≃ 3.5 GPa a phase transition from the initial orthorhombic phase of P21 ab symmetry to an orthorhombic phase of B2cb symmetry was observed. This transition is caused by the complex spatial rotation of the WO6 octahedra. A subsequent isostructural phase transition to another orthorhombic phase of B2cb symmetry was detected at P ≃ 5.9 GPa, accompanied by changes in both the mutual rotation and tilting of the oxygen octahedra with respect to the crystal b axis. Two more pressure-induced phase transitions in Bi2WO6 at high pressures of 11.5 and 20 GPa were observed in the Raman spectra. These pressure-driven phase transitions in bismuth tungstate are accompanied by anomalies in the pressure dependences of the unit-cell parameters, bond lengths and angles, and in the vibrational modes.

On the basis of thermal analysis (DSC, DTA, DTG), single crystal X-ray diffraction experiments, dielectric studies and optical observation, it is found that the (N2H5)3[CdCl5] crystal exhibits several structural phase transitions. At room temperature, the studied crystal exhibits ferroelastic properties and undergoes phase transition from the monoclinic to the orthorhombic phase on heating above 327 K. Upon subsequent cooling, two structural phase transitions at about 323 and 319 K are observed, where the crystal adopts orthorhombic symmetry. The presented phase transitions are unique due to the fact the first heating run results in different structural changes compared to those observed during cooling and subsequent heating/cooling runs. In the studied crystal, N2H5 + ions and 1D chains built up from {CdCl5}3− units bridged by Cl atoms occur. The phase transitions observed can be associated with reorientation of cations and partial disorder of cations as well as Cl atoms.

Lanthanum- and zirconium-doped perovskite Ba0.5Sr0.5Fe0.9Cu0.1O3-δ ceramics, i.e., LaBa0.5Sr0.5Fe1.8Cu0.2O6-δ (LBSFC) and Ba0.5Sr0.5Fe0.85Cu0.1Zr0.05O3-δ (BSFCZ), were synthesized and characterized. The characterizations include x-ray diffraction, scanning electron microscopy, x-ray near-edge absorption spectroscopy of the Fe K-edge and Cu K-edge, iodometric titration, and electrical conductivity measurements. The structure of BSFCZ was pseudo-cubic single perovskite, whereas LBSFC was orthorhombic double perovskite. It was also discovered that the iron and copper in the octahedron-site has a mixed oxidation state with iron having 3+/4+ and copper 2+/3+. The ratio of Fe3+/Fe4+ was found to be 59/41 for LBSFC and 75/25 for BSFCZ. Similarly, copper has a mixed Cu2+/Cu3+ = 24/76 for BSFCZ and 44/56 for LBSFC. The unit cell symmetry, the presence of La3+, and the formation of Fe4+/Cu3+ are thought to be responsible for the improvement in the electrical conductivity and performance of the LBSFC. In contrast, the Zr4- stabilized perovskite structure was unfavorable for electrical conductivity. The electrical performance of the LBSFC achieved a maximum conductivity σ = 150 S/cm-1 at 500°C.