An effective approach to achieve high energy storage density and efficiency in BNT-based ceramics by doping AgNbO3

Abstract

Perovskite dielectric materials for capacitors have received wide attention in recent years because of their fast charge/discharge rates and high power densities. In this work, lead-free relaxor ferroelectric ceramics of (1 − x)[(Bi_0.55Na_0.45)_0.94Ba_0.06]_0.98La_0.02TiO₃–xAgNbO₃ were synthesized by a conventional sintering method. All ceramics are situated at the morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases, suggesting that a small amount of AgNbO₃ (abbreviated as AN) doping does not affect this phase-coexistence structure. The added AN not only improves the dielectric breakdown strength (DBS) from 84.11 kV cm⁻¹ (x = 0) to 137.89 kV cm⁻¹ (x = 0.01), but also broadens the phase transition peak and enhances the relaxation behavior of ceramics. Moreover, when x = 0.01, the ceramic demonstrates a high saturation polarization (P_s) of 25.54 μC cm⁻² and a low remanent polarization (P_r) of 0.65 μC cm⁻² at an electric field of 130 kV cm⁻¹. More importantly, an optimal energy storage density (W_s) of 1.697 J cm⁻³ and energy efficiency (η) of 82.3% are simultaneously achieved in the BNBLT–0.01AN ceramic with excellent thermal stability (∼25–175 °C) and frequency stability (∼10–80 Hz).