Enhanced DC bias stability and thermal robustness in CaSnO3-modified BNKT relaxor ceramics for high-voltage multilayer capacitors

Abstract

Dielectric ceramics with high permittivity, low dielectric loss, and exceptional stability are essential for multilayer ceramic capacitors (MLCCs), which serve as critical components in advanced electronic systems. However, a major challenge in BaTiO₃-based dielectrics is the pronounced capacitance degradation under DC bias, limiting their performance in high-voltage applications. In this study, we design and investigate Bi_0.5(Na_0.8K_0.2)_0.5TiO₃-xCaSnO₃ (BNKT-xCS) ceramics (x = 0–0.2) to address this limitation by enhancing both DC bias and temperature stability. Structural analysis reveals that CaSnO₃ (CS) incorporation disrupts the long-range polarization order, driving a transformation from a nonergodic relaxor (NR) to an ergodic relaxor (ER) state. This transition effectively suppresses domain wall motion, leading to significantly improved bias field resilience. At an optimal composition of x = 0.2, the permittivity variation under ±80 kV/cm bias is minimized to within −10 %–10 %, while excellent thermal stability is maintained across 30–130 °C, with permittivity fluctuations below 10 %. These findings establish BNKT-xCS as a promising lead-free dielectric system for next-generation MLCCs in high-voltage circuits. Beyond advancing the understanding of bias-stable relaxor ferroelectrics, this work introduces a new class of dielectric materials tailored for high-performance energy storage and electronic applications.