Space charge and dielectric behavior of epoxy composite with SiO2-Al2O3 nano-micro fillers at varied temperatures

Dielectric properties at high temperatures are important for epoxy resin used as insulation and package materials operating at varied temperatures in electrical apparatuses and electronic devices. We investigated the dielectric properties of epoxy resin and its composite with SiO2-Al2O3 nano-micro fillers at varied temperatures by combined study of space charge distribution, complex dielectric permittivity and conduction current between 20 and 200 °C. The results show that space charge behavior in epoxy resin and its composite is dominated by electronic charge transport below the glass transition temperature Tg and by ion transport above Tg. The real and imaginary parts of complex permittivity increase to extremely high values at temperatures above Tg. The conduction current increases with a rise in temperature and shows an obvious transition from electronic charge transport below Tg to ionic charge transport above Tg. The composite shows weaker space charge accumulation, lower complex permittivity and conduction current than EP above Tg. Combined analysis of the results indicate that ion accumulation and transport dominate the dielectric properties of epoxy resin and its composite at high temperatures above Tg. The nano-micro fillers in the composite can significantly suppress the ions transport and accumulation.