The dielectric properties of silica at temperature from 300 to 1600 K and at microwave frequency band are investigated.By use of material studio software,the lattice constant,band energy gap and optical permittivity of silica are calculated,and to be used as the key parameters to investigate the microwave dielectric properties of silica.It is found that its permittivity and loss are increased with increasing temperature.In addition,the ionic conduction loss caused by the defects in silica is very small from the calculation and the value is about 10-5 level at 2 000 K.The application of this analysis allows to estimate the permittivity and dielectric loss of silica both at high temperature and microwave band,which is currently still difficult to be measured directly.
This paper presents an analysis of the local electric field in hexagonal boron nitride （h-BN） by introducing a modified parameter. Based on the determination of the modified parameter of h-BN, the revised Lorenz equation is developed. Then the permittivity at high temperature and in the microwave frequency is investigated. In addition, this equation is derived for evaluating the temperature coefficient of the permittivity of h-BN. The analyses show that the permittivity increases with increasing temperature, which is mainly attributed to the positive temperature coefficient of the ionic polarizability.
