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LaAlO3-modified 0.78Bi0.5Na0.5TiO3–0.22Bi0.5K0.5TiO3 (BNKT–xLA, 0 ≤ x ≤ 0.03) piezoelectric ceramics for actuator have been prepared and investigated in this study. With increase in LA substitution, the average long-range crystal structure of the materials gradually develops from rhombohedral–tetragonal mixed ferroelectric phases to a single pseudocubic symmetry. Electrical measurements indicate that the dominant ferroelectric order in unmodified BNKT is severely destroyed and transforms into an ergodic relaxor state with the formation of nanoscale domains, which is further verified by high-resolution transmission electron microscope images. Meanwhile, a great enhanced electric field-induced strain response of 0.36% under 60 kV/cm with a relatively low strain hysteresis is realized at the critical composition x = 0.01. By analyzing the origin of large strain, we believe that the reversible transition of a relaxor state characterized by multiple coexistent nano-domains into an electric field-induced long-range ferroelectric state contributes most to the attainment of these characteristics. [ABSTRACT FROM AUTHOR]

The lead-free (1− x)BiNaTiO- xSrTiO antiferroelectric ceramics were synthesized by two-step sintering method. The influences of SrTiO contents, second sintering temperatures and soaking times on phase structure and energy-storage density were investigated in detail. As the content of SrTiO increases, the ceramics transform from rhombohedral ferroelectric phase into the tetragonal antiferroelectric phase (or pseudocubic phase). The appropriate soaking time and second sintering temperature are beneficial to obtain dense ceramics with fine homogeneous grains, whose the external breakdown electric field and maximum polarization have a large improvement. The optimum electrical performances with low remanent polarization (3.21 μC/cm), a large maximum polarization (31.05 μC/cm), and a large energy density (0.95 J/cm) at 10 Hz were obtained at 1160 °C for BNT-35ST ceramics. [ABSTRACT FROM AUTHOR]