Microstructure-dependent dielectric breakdown in PVDF–BTO composites: A coupled electro-thermo-mechanical phase-field study

Ferroelectric composites are excellent candidates for multifunctional applications owing to the advantages of the synergy between the high polarization of ceramics and the high breakdown strength of polymers. A typical example of them is the poly(vinylidene fluoride)–barium titanate (PVDF–BTO) system. On the other hand, dielectric failure in ferroelectric composites under a high electric field is a complex issue because the failure process is affected by multi-field coupling and the microstructure. In this study, a coupled electro-thermo-mechanical phase-field model was developed to investigate the dielectric breakdown behaviors of PVDF–BTO nanocomposites with varying ceramic filler sizes. The numerical simulations were conducted at 300 K. The results indicate that the breakdown process is primarily controlled by electro-thermal coupling. In contrast, the contribution of mechanical coupling to failure is negligible. The electric breakdown path tends to circumvent the ceramic filler as the BTO particle size increases. In contrast, the maximum internal electric field is significantly enhanced, resulting in a decrease in the overall dielectric breakdown strength. These simulation results are beneficial to understand the microstructure-dependent failure mechanisms of ferroelectric composites, which will be used to design high-reliability composites with high breakdown strength.