Dielectric, thermal, and mechanical properties of CeO2-filled HDPE composites for microwave substrate applications

Abstract

Cerium oxide-filled high density polyethylene (HDPE) composites for microwave substrate applications were prepared by sigma-blend technique. The HDPE was used as the matrix and the dispersion of CeO2 in the composite was varied up to 0.5 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The variations of thermal conductivity (k(eff)), coefficient of thermal expansion (alpha(c)) and Vicker's microhardness with the volume fraction of the filler were also measured. The relative permittivity (epsilon(eff)) and dielectric loss (tan delta) were found to increase with increase in CeO2 content. For 0.4 volume fraction loading of the ceramic, the composite had epsilon(eff) = 5.7, tan delta = 0.0068 (at 7 GHz), k(eff) = 2.6 W/m degrees C, alpha(c) = 98.5 ppm/degrees C, Vicker's microhardness of 18 kg/mm(2) and tensile strength of 14.6 MPa. Different theoretical approaches have been used to predict the effective permittivity, thermal conductivity, and coefficient of thermal expansion of composite systems and the results were compared with the experimental data.