Tailoring relaxor P4bm+P21ma phases in BNT-based ceramics for enhancing comprehensive energy storage properties

Abstract

Tailoring relaxor phase is an effective strategy to enhance energy-storage properties (ESP) for Bi0.5Na0.5TiO3 (BNT)-based ceramics. Herein, we incorporate Na0.91Bi0.09Nb0.94Mg0.06O3 (NBNM) into BNT matrix to form a solid solution of BNT-xNBNM with x = 0.1–0.4. Rietveld refinements reveal that the composition with x = 0.3 has 46% relaxor tetragonal P4bm phase and 54% relaxor orthorhombic P21ma one, thus exhibiting a large normalized energy-storage density (Wrec/E = 0.015 J kV−1 cm−2) and a high efficiency (η = 87%) at 370 kV cm−1. The optimized composition also presents superior temperature stability with a variation of <±5% in the range of 20 °C–150 °C, outstanding frequency reliability with a variation of <±4% in the range of 5 Hz–500 Hz and excellent charge-discharge properties (discharge rate of 76 ns, current density of 1032 A cm−2 and power density of 129 MW cm−3 at 250 kV cm−1). The results demonstrate a successful strategy to design high performance Pb-free relaxor ferroelectrics for pulsed power capacitor applications.