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The 0.72Bi(Fe1−xAlx)O3–0.28BaTiO3 (x = 0, 0.01, 0.03, 0.05, and 0.07, abbreviated as BFAx–BT) lead‐free high‐temperature ceramics were prepared by the conventional ceramic processing. Systematic investigation on the microstructures, crystalline structures, dielectric and piezoelectric properties, and high‐temperature stability of piezoelectric properties was carried out. The crystalline structures of BFAx–BT ceramics evolve from rhombohedral structure with x < 0.01 to the coexistence of rhombohedral structure and pseudocubic phases with x ≈ 0.01, finally to pseudocubic phases when x > 0.03. Remarkably high‐temperature stability with near‐zero temperature coefficient of piezoelectric properties (TCkp), together with improved piezoelectric properties has been achieved for x = 0.01 BFAx–BT ceramics. The BFAx–BT(x = 0.01) ceramics simultaneously show the excellent piezoelectric properties of d33 = 151 pC/N, kp = 0.31 and super‐high‐temperature stability of Td = 420°C, TCkp = 1 × 10−4. It is considered that the observed strong piezoelectricity and remarkably high‐temperature stability should be ascribed to the phase coexistence of rhombohedral and pseudocubic phases. The rhombohedral phases have a positive TCkp value and the pseudocubic phases possess a negative TCkp value. Thus, the TCkp value of BFAx–BT ceramics can be tuned by composition of x.

Lead-free 0.985(0.96KNNT–0.04BNKZ)–0.015CZ ceramics were sintered at 1150–1190 °C.

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BaTiO 3 -(Bi 0.5 Na 0.5 )TiO 3 (BTBNT)-based multilayer ceramic capacitor (MLCC) chips with the inner electrodes being Ag0.6/Pd0.4 are prepared by a roll-to-roll casting method. The BTBNT-based MLCC chips with ten-dielectric layers can be sintered very well at a low temperature of 1130°C via two-step sintering (TSS). X-ray diffraction (XRD) and transmission electron microscope (TEM) resultsshow that MLCC chips are a core-shell structure with two phases coexistence.The core exhibits a tetragonal phase at room temperature and then gradually changes into a cubic phase when the temperature increases above T c (175°C).While, the shell exhibits a pseudocubic phase at all tested temperature from 25°C to 500°C. BTBNT-based MLCC chips exhibit a broad temperature stability and meet the requirement of Electronic Industries Association (EIA) X9R specifications. In terms of energy storage performance, a large discharge energy density of 3.33 J/cm 3 can be obtained at 175°C under the applied electric field of 480 kV/ cm. Among all tested temperature ranging from −50°C to 200°C, the energy efficiency of all chips is higher than 80%, even under a high applied electric field.The experimental results indicate that this novel BTBNT-based X9R MLCCs can be one of the most promising candidates for energy storage applications, especially operated in high temperature. K E Y W O R D Score-shell structure, energy storage, multilayer ceramic capacitor (MLCC), two-step sintering (TSS), X9R

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Lead-free (1 − x)(0.96K0.46Na0.54Nb0.98Ta0.02O3–0.04Bi0.5(Na0.82K0.18)0.5ZrO3)–xCaZrO3 ((1 − x)(0.96KNNT–0.04BNKZ)–xCZ) piezoelectric ceramics were prepared by the conventional solid-state reaction method.