DIELECTRIC LOSS IN MGO AND SAPPHIRE.
Technical rept. no. 1, 1 Jul 63 - 30 Sep 64,
UTAH UNIV SALT LAKE CITY
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Dielectric loss measurements were made on single crystal MgO and sapphire and on pure and doped polycrystalline MgO. The measurements were made in air and in dry argon gas at audio frequencies from room temperature to approximately 800C. Both two- and three-terminal measuring apparatus were used in the investigation. The loss was atmospheric dependent in both single crystal MgO and sapphire. The peaks were attributed to chemisorbed water on the sample. In the case of the polycrystalline MgO samples doped with more than 0.1 cation iron, large conductivities in conjunction with a high resistance between platinum foil electrodes and sample gave rise to interfacial polarization loss peaks. The relaxation time obtained from these peaks was used as a measure of the A.C. conductivity as a function of iron concentration and sample treatment. The activation energy always increased after quenching the samples, and this increase was larger for lower iron concentrations and for faster quench treatment. The conductivity was a very complex function of sample treatment, apparently due to the fast rate of precipitation of ferrities.