Influence of the various doping elements on the microwave dielectric loss of silica

This article presents an evaluation of the influence of various doping elements on the dielectric loss of silica glass. Based on the Anderson–Stuart model, the temperature dependence of the electrical conductivity activation energy was investigated; then, comparisons of microwave dielectric loss of silica doped by various elements such as Li2O, Na2O, K2O, CaO, MgO and Al2O3 are presented. At 1373 K, the dielectric loss of silica doped with Li2O was found to be 10 times more than that the undoped one. The order in the impact of the doping elements on the microwave dielectric loss was found to be Li2O > Na2O > K2O > MgO > CaO > Al2O3. This work is of importance with regard to applications that employ silica glass at conditions that involve especially high temperature and also in the microwave frequency range.

► We investigate the temperature dependence of the electrical conductivity activation energy of various doping elements.
► We study their impact on the dielectric loss of silica glass.
► The influence of impurities on the microwave loss can be defined in the order: Li2O > Na2O > K2O > MgO > CaO > Al2O3.
► Li+ is an important conductivity-enhancing constituent in silica systems.