Energy-storage performance of NaNbO3 based multilayered capacitors

Abstract

Environmentally friendly NaNbO₃ capacitors have a great potential for applications in pulsed-discharge and power conditioning electronic systems because of their AFE-like hysteresis behavior, high saturation polarization and low mass. Here, we demonstrate (0.96 − x)NaNbO₃–0.04CaZrO₃–xBi_0.5Na_0.5TiO₃ (abbreviated as NN-CZ-xBNT) capacitors with high energy storage density (W_rec) and efficiency (η). The performances of capacitors were tuned by the composition induced relaxor behavior and grain refinement which resulted in reduction of hysteresis and increase in the breakdown strength (BDS). Two-step sintering is found to be effective for reducing the grain size of MLCCs to 3 μm, which is 86% smaller as compared to grain size obtained by conventional solid-state sintering (22 μm). Small grain size significantly reduces the leakage current and losses and increases the BDS, yielding excellent W_rec = 3.7 J cm⁻³ and η = 82.1% in the NN-0.04CZ-0.16BNT multilayered capacitors. Results provide a systematic strategy for enhancing the energy storage density and efficiency of dielectric capacitors through the combination of dielectric relaxation and grain size refinement.