The anomalously small dissipation of electromagnetic waves in an ionic crystal

Measurements of the Qe-factors of sapphire disk resonators were made in the 8-10 GHz frequency range at temperatures of 300, 77, and 10 K. The results indicate that in a sapphire ionic crystal the value of tg delta (the tangent of the loss angle of an electromagnetic wave in the crystal) in the microwave range is anomalously small in comparison with the value of tg delta for dielectrics that are commonly used in experimental physics. It is suggested that sapphire ring resonators show promise as tools in microwave spectroscopy.