Dielectric and electromagnetic properties of amorphous PDCs-Si(Al)CNO with different Al contents in X-band

Abstract

Amorphous polymer-derived Si(Al)CNO ceramics with different Al contents were successfully prepared using polyvinylsilazane (PVSZ) doped with different mass fractions (0 to 15 wt%) of aluminum tri-sec-butoxide (ASB) as the precursors. The thermogravimetric, crystal morphology, microstructure, electrical conductivity and dielectric properties of Si(Al)CNO ceramics were characterized and tested, respectively. The results show that the porosity of Si(Al)CNO ceramics first decreased and then increased with the increase of ASB doping content. The electrical conductivity of SiAlCNO-5, SiAlCNO-10 and SiAlCNO-15 ceramics gradually decreased from 2.80 × 10-9 to 0.89 × 10-9 (Ω cm)-1. Their conductivity was related to free carbon in the ceramics based on Raman spectroscopy. The average permittivity of SiCNO, SiAlCNO-5, SiAlCNO-10 and SiAlCNO-15 ceramics gradually increased from 3.63 to 3.93 with the increase of ASB doping content in X-band. The dielectric loss of SiAlCNO ceramics doped with ASB was smaller than that of SiCNO ceramics. But with the continuous increase of ASB doping content, the dielectric loss of SiAlCNO ceramics also increased. The permittivity and dielectric loss of Si(Al)CNO ceramics were related to their porosity and electrical conductivity. The average absorption coefficient of Si(Al)CNO ceramics were less than 0.020, while their transmission coefficient were greater than 0.500. It was found that the amorphous Si(Al)CNO ceramics exhibit good electromagnetic wave transmission properties.