Enhanced energy storage properties of BiAlO₃ modified Bi_0.5Na_0.5TiO₃–Bi_0.5K_0.5TiO₃ lead-free antiferroelectric ceramics

Lead-free (1−x)(0.75Bi_0.5Na_0.5TiO₃–0.25Bi_0.5K_0.5TiO₃)–xBiAlO₃ (BNT–BKT–100xBA, x=0–0.10) ceramics were prepared by two-step sintering method and their phase structure, micro morphology and electrical properties were systematically investigated. X-ray diffraction analysis indicates a pure perovskite phase for x≤0.06 as well as a structural evolution from a tetragonal toward a pseudocubic phase. Transmission electron microscopy study of the x=0.04 composition reveals the existence of antiferroelectric phase with a⁰a⁰c⁺ oxygen octahedron tilting which is in the form of nano-domains. Polarization-electric field and current-electric field hysteresis loops demonstrate that the increase of BA concentration destroys the ferroelectric order and strengthens antiferroelectric order. A much enhanced energy storage density of 1.15 J/cm³ and efficiency of 73.2% is achieved under 105 kV/cm at x=0.06. In addition, its energy storage property is found to depend weakly on temperature within the measurement range of 25–150 °C.