Distinct dielectric responses in BaTiO3-Bi0.5Na0.5TiO3-CaBi4Ti4O15 composites across different compositional regimes

Abstract

High-temperature capacitors require dielectric materials that combine high permittivity with stable capacitance over broad temperature ranges, yet conventional perovskite oxides suffer from intrinsic limitations associated with low Curie temperatures and sharp phase transitions. Here, we report a composite dielectric strategy that integrates a high-Tc Aurivillius phase, CaBi4Ti4O15 (CBT), into BaTiO3-Bi0.5Na0.5TiO3 (BT-BNT) perovskite matrices spanning morphotropic phase boundary (0.06BT-0.94BNT) and BT-rich (0.90BT-0.10BNT) compositions. Structural and microstructural analyses reveal phase-separated perovskite-Aurivillius composites without significant interdiffusion, generating interfacial strain and defect-mediated effects that suppress dielectric dispersion and flatten phase-transition features. In particular, the optimized 90BT/10BNT/10CBT composition exhibits a high dielectric constant of epsilon(r) ti 1214 and an exceptionally high maximum operating temperature of 473 degrees C within +20% capacitance variation, while maintaining low dielectric loss. These results establish Aurivillius-perovskite composite engineering as an effective pathway for high-temperature capacitor applications.