The dielectric properties and dielectric mechanism of perovskite ceramic CLST/PTFE composites

摘要

Polytetrafluorethylene (PTFE) composites filled with perovskite (Ca,Li,Sm)TiO_3 (CLST) dielectric ceramic of various volume fractions filler up to 60% were prepared. The effects of volume fraction of ceramic filler on the microstructure and dielectric properties of the composites have been investigated. A comparative study of dielectric properties of experiment and modeling analysis has been carried out at high frequencies for the CLST/PTFE composites. The results indicate that both the dielectric constant and the dielectric loss increase with the filler. The CLST/PTFE composite with 40% ceramic has exhibited good dielectric properties: ε_r = 7.92 (~10 GHz), tan δ = 1.2 × 10~(−3) (~10 GHz), and τ_f = −45 ppm/°C. The dielectric properties are obviously better than most composites reported previously at high frequencies in the aspects of dielectric loss and thermal stability. The dielectric constant and dielectric loss of composites predicted by the Rother-Lichtenecker equation and the general mixing model are in good agreement with the experiment data when the volume fraction of ceramic is less than 40%. When the volume fraction of the ceramic is more than 40%, the deviation occurs. By introducing the correction factor, the theoretical values of the dielectric constant agrees well with the experimental values.