Simultaneously High Dielectric Constant and Breakdown Strength in CaCu3Ti4O12-Filled Polymer Composites

Although adopting giant-permittivity ceramic fillers results in a high dielectric constant in polymer-based composite materials, high dielectric loss and low breakdown strength are easily triggered. In this study, the dielectric and breakdown characteristics were optimized by designing and preparing polymer/giant-permittivity ceramic/insulating ceramic ternary composite films. Copper calcium titanate (CCTO) and boron nitride (BN) were used as the giant-permittivity and highly insulating fillers, respectively. The ternary composite films exhibited improved overall electrical properties compared with the binary polymer/CCTO composite films. The synergistic effect between CCTO and BN fillers was found to be crucial. At 100 Hz, the optimal ternary composite film containing 40 wt.% CCTO filler and 3 wt.% BN filler exhibited a high dielectric constant of approximately 68 and low dielectric loss of approximately 0.19, and high electrical breakdown strength of approximately 175 MV m−1 under a direct-current electric field. This study may boost the large-scale fabrication of high-performance composite dielectric film materials for electrical energy storage.