Microwave dielectric properties of PTFE/CaTiO3 polymer ceramic composites

CaTiO3 ceramic powder filled polytetrafluoroethylene (PTFE) composites with various filler volume fractions up to 60 vol.% were prepared. The effects of volume fraction of the ceramic filler on the microstructure and microwave dielectric properties of the composites were investigated in detail. As the volume fraction of the ceramic filler increases, the dielectric constant (epsilon(r)) and the temperature coefficient of resonant frequency (tau(f)) of composites increase, while the product of quality factor and frequency (Q x f) decreases. Composites with 40 vol.% CaTiO3 exhibited good microwave dielectric properties: epsilon(r) = 13 at similar to 5 GHz, Q x f = 930 GHz, and tau(f) = 260 ppm/degrees C. Different mixing rules were used to predict the dielectric constant of composites, and it was found that the dielectric constants predicted by Effective Medium Theory (EMT) were in good agreement with experimental data. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.