The temperature variation of the dielectric constant of ’’pure’’ CaF2, SrF2, BaF2, and MgO

Improved values of the real part of the low-frequency dielectric constant are presented for ’’pure’’ CaF2, BaF2, SrF2, and MgO over the temperature range 5.5-400 K. Accurate measurements of both the real and imaginary parts of the dielectric constant were made so that corrections could be made to allow for dipolar impurities. The final results are thought to be accurate to better than 0.1% over the full range of temperatures.