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One of the inherent disadvantages of Bi0.5Na0.5TiO3‐based (BNT‐based) piezoceramics is that an increment of the depolarization temperature (Td) is generally accompanied by a deterioration of the temperature stability of the real‐time piezoelectric constant (d33), which severely restricts the practical applications of the materials. Herein, we propose a new strategy to mitigate the conflict between the elevation of Td and the temperature stability of the real‐time d33 in BNT‐based ceramics via integrating the pressure‐assisted sintering and quenching process. By this strategy, we not only increased the Td from 109 to 166°C but also improved the temperature stability of the real‐time d33 (the temperature coefficient Ttc = ± 13 pC/N) in 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 ceramic. Both the built‐in field and the increment of the field‐induced R3c phase fraction play the significant role in enhancing the Td and the temperature stability of the real‐time d33. Thus, our work provides a simple and effective approach for designing piezoceramics with high Td and a superior temperature stability of the real‐time d33. [ABSTRACT FROM AUTHOR]

In the process of exploring ferroelectric semiconductors, a new system of (1−x) KNbO3–xSrFeO3−δ (x = 0.00‐0.20) was successfully synthesized via solid‐state reaction. The crystal structures, ferroelectric, dielectric, optical, and electrical properties were systematically characterized. The orthorhombic phase with Amm2 space group is detected in all the ceramics. In addition, the orthorhombic and tetragonal phases coexist in 0.80KNbO3‐0.20SrFeO3‐δ ceramic. The decrease in oxygen octahedron distortion induces a weak ferroelectric polarization. The existence of long‐range ferroelectric polarization order in all the ceramics is verified and the bandgap of the ceramics can be tuned to ~2.18 eV. The improved short‐circuit photocurrent density (Jsc) and open‐circuit voltage (Voc) of the poled 0.95KNbO3‐0.05SrFeO3−δ ceramic at 30 kV/cm are ~6.90 nA/cm2 and 0.04 V, respectively. The activation energies for electrical conductivity of the grains and grain boundaries from 0.90KN–0.10SF ceramic are 0.67 and 0.77 eV, respectively, which indicate the doubly ionized oxygen vacancies. This work provides a new way to tune the optical bandgap/ferroelectric properties of KNbO3‐based ceramics for potential application in ferroelectric photovoltaic and energy fields. [ABSTRACT FROM AUTHOR]

Large Na0.5K0.5NbO3 ( NKN) piezoelectric single crystals were obtained by seed-free solid-state crystal growth method, which is a traditional sintering grain growth process, with LiBiO3 used as a sintering aid. The largest dimension of the single crystals obtained was 11 mm × 9 mm × 3 mm. In addition to the LiBiO3 doping content, temperature, and time effect of the crystal growth process was systematically investigated and considered from the kinetics point of view. With the assistance of Avrami analysis, parameters relevant to the crystal growth process were determined. Laue diffraction and transmission electron microscopy suggested an orthorhombic symmetry for the single crystalline structure. Dielectric-frequency-temperature measurements revealed an orthorhombic-tetragonal and tetragonal-cubic phase transition at 155°C and 405°C, respectively, both of which are typical of first-order transitions, and have a well-defined thermal hysteresis. Rayleigh analysis was performed regarding to the extrinsic reversible and nonreversible piezoelectric properties, and the result suggested a dominant intrinsic reversible piezoelectric contribution of 91.5% under E0 = 1 kV/cm AC amplitude. Such a single crystal growth process route is low cost and a relative simple preparation process. [ABSTRACT FROM AUTHOR]

The subsolidus phase relations of the BaO- Y2 O3- MnO2 system have been investigated in air. There are eight binary compounds, a new ternary compound and 11 three-phase regions in this system. The ternary compound with the BaO: YO1.5: MnO2 molar ratio of 8:2:5 was indexed by a rhombohedral lattice with a = 5.7929 (6) and c = 28.586 (4) Å. The synthesized compounds were determined to be stoichiometric except for the Ba1− x Y x MnO3 phase ( x ≤ 0.01). [ABSTRACT FROM AUTHOR]

Large Na0.5K0.5NbO3 ( NKN) piezoelectric single crystals were obtained by seed-free solid-state crystal growth method, which is a traditional sintering grain growth process, with LiBiO3 used as a sintering aid. The largest dimension of the single crystals obtained was 11 mm × 9 mm × 3 mm. In addition to the LiBiO3 doping content, temperature, and time effect of the crystal growth process was systematically investigated and considered from the kinetics point of view. With the assistance of Avrami analysis, parameters relevant to the crystal growth process were determined. Laue diffraction and transmission electron microscopy suggested an orthorhombic symmetry for the single crystalline structure. Dielectric-frequency-temperature measurements revealed an orthorhombic-tetragonal and tetragonal-cubic phase transition at 155°C and 405°C, respectively, both of which are typical of first-order transitions, and have a well-defined thermal hysteresis. Rayleigh analysis was performed regarding to the extrinsic reversible and nonreversible piezoelectric properties, and the result suggested a dominant intrinsic reversible piezoelectric contribution of 91.5% under E0 = 1 kV/cm AC amplitude. Such a single crystal growth process route is low cost and a relative simple preparation process. [ABSTRACT FROM AUTHOR]