Frequency-Temperature-Angle Characteristics of AT-Type Resonators Made of Natural and Synthetic Quartz

Investigations into the frequency-temperature behavior of AT-type quartz resonators have revealed differences between natural and synthetic quartz. The differences refer mainly to a shift of the optimum angle of orientation by a few minutes of arc and to a slight change of the frequency-temperature characteristic itself. To describe the frequency-temperature behavior analytically, the measured change of frequency vs temperature can be developed in a power series, determined by first, second, and third-order temperature coefficients. In the temperature range from -60 to +100°C. higher-order temperature coefficients can be neglected. For a large number of AT-type resonators of various angles made from natural and several kinds of synthetic quartz, the temperature coefficients, and their variation with the angle have been determined. It is possible to modify the properties of synthetic quartz by introducing other elements during the growing process. An example is quartz grown in an alkaline solution containing germanium dioxide. Measurements have been made on AT-type resonators cut from such synthetic quartz. The third-order temperature coefficient for the AT-type resonator is found noticeably reduced; the frequency-temperature curves are flattened over a wider temperature range.