Effect of Ba(Zn1/3Ta2/3)O3 and SiO2 ceramic fillers on the microwave dielectric properties of butyl rubber composites

Abstract

Butyl rubber–Ba(Zn1/3Ta2/3)O3 (BR–BZT) composites and butyl rubber–silica (BRS) composites were prepared by sigma mixing. The dielectric properties at 1 MHz and 5 GHz of BR–BZT and BRS composites were investigated as a function of ceramic loading and were found to be improved with filler loading. For a optimum BZT loading of 0.26 vf, the BR–BZT composite have er = 4.88, tand = 0.0022 (at 5 GHz), coefficient of thermal expansion (CTE) = 112 ppm/ C, thermal conductivity (TC) = 0.30 Wm-1 K-1 and water absorption = 0.047 vol%. The BRS composites attained er = 2.79, tand = 0.0039 (at 5 GHz), CTE = 102 ppm/ C, TC = 0.40 Wm-1 K-1 and water absorption = 0.078 vol% for the same loading of silica. The stress–strain curves of both composites showed good flexibility of the composite. The measured relative permittivity and TC of both composites were compared with different theoretical approaches.