Low Dielectric Loss Polytetrafluoroethylene/TeO 2 Polymer Ceramic Composites

TeO 2 particle‐filled PTFE composites were prepared by the powder processing technique. The structure and microstructure of the composites were investigated by X‐ray diffraction and scanning electron microscopic methods. The effect of the ceramic content (0–0.6 volume fraction) of TeO 2 on the dielectric properties of the composites was studied at 1 MHz and 7 GHz. The dielectric constant and dielectric loss increased with an increase in the TeO 2 content. For 60 vol% of TeO 2 , the composite has a dielectric constant of 5.4 and a loss tangent of 0.006 at 7 GHz. The measured dielectric constant (ɛ r ) is compared with the effective dielectric constant calculated using different theoretical models. The observed dielectric constants are in agreement with that calculated using effective medium theory. The coefficient of thermal expansion of the composites decreases with the TeO 2 content, reaching a minimum of 32 ppm/°C for 60 vol% loading.