Finite difference simulations of permittivity and electric field statistics in ceramic-polymer composites for capacitor applications

Finite difference quasielectrostatic modeling is used to predict the complex dielectric permittivity of barium titanium oxide (BTO)-polymer composites of interest for capacitor applications. The simulations explore the effects of the microstructural arrangement of spherical ceramic particles, the volume filling fraction of ceramic, and the type of polymer on the composite permittivity. For composites with randomly positioned ceramic particles, a soft percolation regime is found between volume filling fractions of 0.35 and 0.5 that leads to a more gradual growth in permittivity compared to ordered arrangements of particles. For BTO dispersed in a representative relaxor ferroelectric polymer, dielectric constants as high as 300 are predicted at a filling fraction of 0.45. Electric field statistics inside the composites are also computed, and localized intensification factors in the range of three to eight times the applied field are predicted, with an incrementally linear growth in high-field probability with increasing filling fraction in the soft percolation regime. The deleterious effect of air voids on composite permittivity is also explored. (C) 2006 American Institute of Physics.