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This investigation highlights the significant influences of alkaline earth ion substitution for Gd on the structure, vacancy defects, magnetic and dielectric properties in GdMnO 3 (GMO) ceramics synthesized using the solid-state reaction method. The structure measurements indicate that all of the Gd 0.90 A 0.10 MnO 3 (A = Ca, Sr, Ba) samples show a single phase structure, and the introduction of A 2+ ion induces structure distortion. A 2+ ions substitution increases the Mn4+ ion concentration in GMOs, but has no significant effect on the oxygen vacancy concentration. All samples with irregular grain shapes have dense microstructures, and A 2+ ion substitution inhibits grain growth. Positron annihilation experimental results indicate that A 2+ ion substitution can increase the vacancy size and concentration, while the vacancy concentration increases first and then decreases with increasing A 2+ ion radius. The evolution of the temperature- and magnetic field-dependent magnetization curves shows that A 2+ ion substitution could obviously affect the magnetic state of GMOs, and improve the magnetic transition temperature and magnetization of Gd 0.90 A 0.10 MnO 3. The dielectric measurements reveal that the A 2+ ion substituted samples exhibit giant dielectric constant characteristics over a broad frequency range. It is found that the enhanced magnetization of Gd 0.90 A 0.10 MnO 3 has a close relationship with the vacancy concentration, and the giant dielectric constant behaviors in Gd 0.90 A 0.10 MnO 3 ceramics can be associated with the mixed-valent structure of Mn3+/Mn4+. [ABSTRACT FROM AUTHOR]

High-entropy oxides with complex compositions can be designed as new ferroelectric materials with interesting physical consequences. Here, a series of high-entropy perovskite ceramics (Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO 3 , Bi 0.2 Li 0.2 Ba 0.2 Sr 0.2 Pb 0.2 TiO 3 , Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Pb 0.2 TiO 3 , Bi 0.2 K 0.2 Ba 0.2 Sr 0.2 Pb 0.2 TiO 3 , and Bi 0.2 Ag 0.2 Ba 0.2 Sr 0.2 Pb 0.2 TiO 3) was proposed, which selected various elements to diminish the formational enthalpy and thus to achieve a single-phase structure. Detailed crystal structure and microstructure characterizations indicated that the high-entropy perovskites exhibited a single tetragonal phase with excellent chemical homogeneity. The equiatomic ratios of the A-site cations in perovskites could be used to maximize the entropy stabilization effect and effectively disordered the symmetry of the crystal structure. A robust ferroelectric polarization reaching 20 μC/cm2 under 50 kV/cm was achieved in Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Pb 0.2 TiO 3 high-entropy ferroelectrics. This work provides an effortless approach to discover new high-entropy ferroelectrics in materials with unexplored compositional complexity and gives additional opportunities to design and tailor the functional properties in entropy-stabilized ferroelectrics. [ABSTRACT FROM AUTHOR]

Piezoelectric catalysis is the catalytic action driven by the force-electrical conversion of piezoelectric materials. In this paper, the piezoelectric activity of K 0.5 Na 0.5 NbO 3 (KNN) was thoroughly investigated by annealing KNN at a series of temperatures and poling KNN under different electric-fields. With the application of an ultrasonification, the degradation activity for the Rhodamine B (RhB) dye molecules of the poled KNN was 253% higher than that of unpoled samples. The piezocatalytic activity of the poled KNN was significantly improved, which stemmed from the orderly ferroelectric domain to effectively reduce the recombination rate of the carriers by the built-in electric field. In addition, the superior piezocatalytic activity was achieved at KNN materials with the average grain size of ~0.29 μm, and after 160 min of mechanical vibration, the degradation rate of RhB (~5 mg/L) was as high as 95.7%. The high mechanical catalytic degradation rate of KNN materials reveals a bright application prospects in vibration catalytic degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Ceramic-based dielectrics are considered as the best candidates for high temperature capacitors because of their outstanding mechanical and electrical properties. Nevertheless, conventional barium titanate-based capacitors show narrow operating temperature ranges owing to the low tetragonal-cubic phase transition temperature. In order to increase the working temperature and relative permittivity, a novel (1- x)Na 0.5 K 0.5 NbO 3 - x La(Zn 0.5 Ti 0.5)O 3 (NKN- x LZT) ceramics were chosen to meet the targets in this work. The NKN- x LZT ceramics with sub-micrometer grains (0.2–0.4 μm) were synthesized via a conventional solid-state sintering route. A relative permittivity (ε ' = 1560 ± 15%) with low loss tangent over wide temperature range from 96 °C to 350 °C was obtained in the x = 0.02 ceramics. Additionally, the crystal structure distortion and conduction behaviors of the NKN- x LZT ceramics were systematically studied. The decrease of oxygen octahedron distortion induced a weak polarization, and the high resistance (9 × 106 Ωcm at 400 °C) greatly suppressed the long-term migration of defective ions in the ceramics. Therefore, the low loss tangent and high permittivity were still stabilized at the high temperature. It believes that the NKN- x LZT ceramic system in this work will become one of the most promising candidates for high-temperature capacitor devices. [ABSTRACT FROM AUTHOR]

This paper utilizes the TFA-MOD (Trifluoroacetate Metal-Organic Decomposition) method to prepare YB 2 C 3 O 7-δ (YBCO) superconducting films on a LaMnO 3 metal substrate. Using a self-made process curve, we investigate the nucleation and growth orientation of crystals at various temperatures under specific oxygen partial pressures (P O2). We successfully obtain an oxygen partial pressure-temperature phase diagram at a fixed time. This diagram provides critical insight into the trends that guide our regulation of parameters to ultimately achieve a relatively pure a -axis oriented YBCO film. Temperature and nucleation rate are important parameters that influence crystal nucleation orientation. The key conditions for producing a -axis-oriented YBCO films include low temperature, high Δ μ , and extended crystallization time. [ABSTRACT FROM AUTHOR]

Copper calcium titanate (CaCu 3 Ti 4 O 12 , CCTO) ceramics are receiving a great deal of attention for advanced electronic and energy storage device applications owing to their giant permittivity response and good temperature stability. However, the development and real applications of CCTO ceramics are generally restricted by their large dielectric loss and low breakdown electric field strength. In the present study, a novel type of perovskite-like Na 1/3 (Ca 1/2 Sr 1/2) 1/3 (Bi 1/2 Y 1/2) 1/3 Cu 3 Ti 4 O 12 (NCSBYCTO) ceramics were designed via multiple elements strategy based on the high-entropy concept. Consequently, all the NCSBYCTO ceramics present a giant permittivity response (103∼104), good stability of temperature and frequency, and remarkable relaxation characteristics, especially the NCSBYCTO ceramic sintered at 1050 °C exhibits a relative balance between the giant permittivity of about 7.0 × 103–9.5 × 103 and the lower dielectric loss of approximately 0.043–0.294 at a frequency range of 104–106 Hz under room temperature. Furthermore, all the NCSBYCTO ceramics present an obvious nonlinear characteristic. More encouragingly, a higher breakdown field strength of around 2552.56 V/cm accompanied by a larger nonlinear coefficient of about 6.48 is achieved in the NCSBYCTO ceramic sintered at 1070 °C. A significant electrical heterogeneity structure and electron defect structure induced by the existence of mixed-valence Cu+/Cu2+ and Ti3+/Ti4+ are also found in the NCSBYCTO ceramics. The giant permittivity response, low dielectric loss and improved nonlinear properties can be considered the synergistic effect of the defect mechanism and the internal barrier layer capacitor model. This finding offers a route for designing giant permittivity ceramics with brilliant dielectric properties and nonlinear behaviors, which is expected to benefit dual-functional device applications of capacitors and varistors. [Display omitted] • A novel type of Na 1/3 (Ca 1/2 Sr 1/2) 1/3 (Bi 1/2 Y 1/2) 1/3 Cu 3 Ti 4 O 12 perovskite-like ceramics were developed via multiple elements strategy. • All the NCSBYCTO ceramics exhibit a giant permittivity response (103∼104) and good stability of temperature and frequency. • A relative balance between the giant permittivity and a lower dielectric loss is achieved in the NCSBYCTO ceramic sintered at 1050 °C. • The NCSBYCTO ceramic sintered at 1070 °C shows a higher E b of 2552.56 V/cm and a larger α of 6.48. • The electron defect mechanism and IBLC model can synergistically explain the enhanced electrical properties. [ABSTRACT FROM AUTHOR]

One of the primary challenges in high-power devices is the issue of heating, which is caused by energy loss resulting from domain wall motion. To address this problem, our study established a electromechanical hardening approach by integrating NiO into Na 1/2 Bi 1/2 TiO 3 (NBT). This method leads to the in-situ formation of the second phase within grains and between the grain boundaries. The second phase inside the grains inhibits the domain wall motion and reduces the mechanical loss, resulting in a considerable increase in mechanical quality factor (Q m) by over 80%. Additionally, the introduction of NiO notably enlarges the grain size by more than 4.5 times. The combination of the second phase and the increased grain size synergistically preserves piezoelectric coefficients (d 33). Our study uncovers an innovative method to enhance Q m without significantly compromising d 33. [ABSTRACT FROM AUTHOR]

Lead-free (Ba 0.85 Ca 0.15)(Ti 0.90 Zr 0.10)O 3 (BCZT)-based piezoelectric ceramics have attracted considerable interest due to their excellent piezoelectric properties and abundant phase structures. However, there is a serious lack in the theoretical calculations for the ferroelectric phase transition behavior. Here, the experimental and first-principles calculations were utilized to analyze the ferroelectric phase transition process of (Ba 0.85 Ca 0.15)(Ti 0.90 Zr 0.10)O 3 - x Gd 2 O 3 (BCZT- x Gd, x = 0, 0.02, 0.04, and 0.05) ceramics. The incorporation of Gd 2 O 3 has induced a transformation from tetragonal to rhombohedral phase due to the decrease in the dislocation energy with A-site cations and the attenuation of the bonding energy between B-site cations and the planar O atoms. Moreover, the hybridization between the d orbitals of B-site atoms and the O 2p orbitals, coupled with the reduction of the polarization vector along the [001] axis, leads to enhanced weak coupling relaxation. This work provides a theoretical basis for the ferroelectric phase transition behavior of other piezoelectric systems. [ABSTRACT FROM AUTHOR]

Dielectric energy storage materials have a high power density, which has attracted much attention in many fields, such as pulsed power generation and electric vehicles etc. As a typical and traditional energy storage material, barium strontium titanate (Ba 1- x Sr x TiO 3) has been widely used in this field. However, its energy storage density is extremely low. In this work, (1- x)Ba 0.4 Sr 0.6 TiO 3 - x BiFeO 3 ceramics (x = 0.05, 0.10, 0.25) were prepared by the traditional solid-state method. The results show that the energy storage density of the 0.90Ba 0.4 Sr 0.6 TiO 3 -0.10BiFeO 3 ceramic with average grain size of 1.5 μm is 3.1 J/cm3, and the efficiency is 74.1% at a low electric field of 240 kV/cm. In addition, the energy storage density of the 0.95Ba 0.4 Sr 0.6 TiO 3 -0.05BiFeO 3 ceramic can be as high as 3.29 J/cm3. The energy storage efficiency can reach 90.69% in the electric field of 300 kV/cm. It can be concluded that the addition of BiFeO 3 can greatly enhance the energy storage property of Ba 0.4 Sr 0.6 TiO 3 , which indicates that Ba 1- x Sr x TiO 3 ceramics with BiFeO 3 will be good candidates in the field of power electronics. [ABSTRACT FROM AUTHOR]

The emerging high-entropy oxides (HEOs) have been considered promising candidates in numerous applications due to their unique properties. Yet the dielectric properties of HEOs at high pressure remain to be disclosed. In this work, the dielectric properties of (FeCoCrMnZn) 3 O 4 at high pressures up to ∼20 GPa were systematically investigated. Combined with in-situ Raman, XRD, and impedance measurements, it is revealed that high-pressure exhibits a significant impact on the dielectric properties, even without the observed phase transition. The electric resistance, which is dominantly contributed by grain resistance, decreases exponentially with the increase of pressure. On the other hand, the relative permittivity decreases linearly with increasing pressure. In addition, the dielectric relaxation behavior of (FeCoCrMnZn) 3 O 4 at high pressure is revealed. Our results provide the experimental basis for the high-pressure effect on the dielectric properties of (FeCoCrMnZn) 3 O 4 and potential guidance for the design strategy of HEOs under extreme conditions. [ABSTRACT FROM AUTHOR]

Electrode selection and its effects are extremely crucial to characterize the electrical properties and understand the colossal permittivity response of CaCu 3 Ti 4 O 12 (CCTO) ceramics. However, the specifical correlation between metal electrode and electrical performances of CCTO ceramics are not clear so far. In this study, we have systematically investigated the effects of metal electrodes (Ag, Au and Pt) on the colossal permittivity response, dielectric loss, nonlinear characteristics and dielectric relaxation behavior of CCTO ceramics prepared via solid-state reaction means. Moreover, the related physical mechanisms of electrode effect on the electrical properties of CCTO ceramics have been analyzed. As a result, it is found that the metal electrode plays a minimal effect on the dielectric constant of CCTO ceramics in low and intermediate frequencies (102–105 Hz), but the Pt-CCTO ceramic presents a reduced dielectric constant in a frequency range of 104–105 Hz due to the relatively weaker grain boundary responses and the lower Schottky barriers between Pt electrode and sample surface. Meanwhile, the dielectric constant of Pt-CCTO ceramics sharply decreases at the high frequencies, which may be attributed to the greater dipole-dominated dielectric relaxation behaviors induced by the Pt electrode. Furthermore, the influence of electrode on dielectric loss is relatively significant, especially at the intermediate and high frequencies under high temperatures. Whereas, the influences of electrode effect on the breakdown electric field strength and nonlinear coefficient of CCTO ceramics are relatively little, as revealed by nonlinear characteristics. Consequently, it is comprehensively considered that the Ag electrode is more suitable to characterize the electrical performances of CCTO ceramics. Our results may provide a guidance to select electrodes and further understand the colossal dielectric mechanism for all the dielectric ceramics. [ABSTRACT FROM AUTHOR]

Relaxor-ferroelectric (RFE) ceramics possess slender ferroelectric hysteresis loop and low remnant polarization (P r). They have great potential to provide excellent energy-storage performance as dielectric energy-storage materials. Herein, a lead-free 0.8Ba 0.4 Sr 0.6 TiO 3 –0.2Sr 0.7 Bi 0.2 TiO 3 (0.8BST–0.2SBT) RFE ceramic with high energy-storage performance has been realized successfully. The addition of Bi3+ and increase in Sr2+content at the A site of the BST can effectively inhibit the growth of grains for high breakdown strength (E b). As a result, an ultrafine average grain size of 0.7 μm was obtained in 0.8BST–0.2SBT RFE ceramic, affording a high E b of 300 kV/cm. Further investigation revealed that the mutual conversion of short-range polar nanoregions and long-range-ordered ferroelectric domains upon application and withdrawal of a 300 kV/cm applied electric field resulted in a high maximum polarization (P max) of 31 μC/cm2 and a low P r of 2.5 μC/cm2. Hence, the 0.8BST–0.2SBT RFE ceramic simultaneously exhibited a high recoverable energy-storage density of 3.3 J/cm3 and a high energy-storage efficiency of 85% at 300 kV/cm. Additionally, a good energy-storage performance was reported over a temperature range of 50°C-120 °C and frequency from 10 to 1000 Hz, making the 0.8BST-0.2SBT RFE ceramic a potential lead-free dielectric energy-storage material. [ABSTRACT FROM AUTHOR]

(1-x)(K 0.49 Na 0.49 Li 0.02 )(Nb 0.8 Ta 0.2 )O 3 -xCaZrO 3 (x=0, 0.025, 0.05 and 0.075, abbreviated as KNLNT-1000xCZ) ceramics were prepared by a solid state method. The correlations between phase constitution, domain configuration and tunable dielectric properties are investigated. Due to the combined effects of multi-phase coexisting and nanoscaled domain, KNLNT-50CZ has a high dielectric tunability (60.0%) at the room temperature and 1 kHz under the electric field of 30 kV/cm. More importantly, the high tunability can be maintained stable in the temperature range of 25–150 °C with a smaller variation of ± 10%, which is superior to most of other tunable dielectric materials. The excellent temperature stability in tunable dielectric properties is ascribed to the diffused phase transition and coexistence of multi-phases in this temperature range. Therefore, our work has provided a new promising candidate for temperature-independent tunable dielectric materials. [ABSTRACT FROM AUTHOR]

Lead-free piezoceramics (Na (1+ x )/2 Bi (1- x )/2 ) 0.94 Ba 0.06 Ti 1- x Nb x O 3 (BTN100 x ) were prepared using conventional solid-state reaction method. The structures, field- induced strain, AC impedance of sintered ceramics were investigated. The pure perovskite solid solution BTN3 exhibited giant electric-field-induced strain of 0.478% under an electric field of 70 kV/cm at ambient temperature, meanwhile, the normalized strain ( S max / E max ) reached up to 654 pm/V. The giant strain was insensitive to temperature and exhibited excellent fatigue resistance performance within 10 6 switching cycles, making it a promising candidate material for actuator applications. Complex AC impedance spectra confirmed the contribution of grain effect to resistivity behavior. The field-induced giant strain was attributed to the phase transition between ferroelectrics and relaxor ferroelectrics induced by introducing Nb 2 O 5 . [ABSTRACT FROM AUTHOR]

x CeO 2 -doped Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 lead-free piezoelectric ceramics (BNTC1000 x , x =0, 0.3, 0.6, 0.8, 1.0, 1.2, 1.4 wt%), were synthesized by the solid-state reaction method. XRD patterns showed that all BNTC1000 x ceramics exhibit pure single perovskite phase. At the critical composition BNTC12, a large electric-field-induced strain of 0.39% with normalized strain ( S max / E max ) of 561 pm/V was obtained under an electric field of 65 kV/cm. The ferroelectric phase was fully poled with electric field, and depoled once the applied electric field was removed. During that cycle, the non-180°-domains repeated switching and back-switching and the large strain was induced. The relaxation behavior was involved in BNTC1000 x ceramics and induced by oxygen vacancy migration. Besides, this behavior was more predominant in BNTC12 than in BNTC0. [ABSTRACT FROM AUTHOR]