Tetra-needle zinc oxide/silica composites: High-temperature dielectric properties at X-band

Nano-structural ZnO of unique electrical and optical properties is highly attractive in dielectric and microwave applications, specifically considered as ideal fillers for achieving light-weight composites. In this work, tetra-needle ZnO (T-ZnO) by a direct combustion approach was selected as the filler in silica nanopowders for fabricating T-ZnO/SiO2 composites. Temperature effects on dielectric properties of the composites were investigated in the temperature range of 300–700 °C at 8.2–12.4 GHz. The observed imaginary permittivity and loss tangent was found to be temperature dependent, and the mechanism associated with relaxation and electrically conductive loss was discussed.

► High-temperature dielectric properties of ZnO composites.
► Temperature-dependent dielectric loss.
► Enhanced properties by polarized relaxation and electrically conductive loss.