Zero temperature coefficient quartz crystals for very high temperatures

In order to determine the angles of cuts for low temperature coefficient crystals, the elastic constants of quartz have been evaluated in the temperature range from −100°C to +200°C. This has been done by measuring a series of rotated Y-cut crystals in the thickness shear mode and a series of rotated X-cuts in the longitudinal length mode. From the measurements, low temperature coefficients AT, BT, CT, and DT type crystals can be determined which have their temperature of zero temperature coefficient at any prescribed temperature. Calculations are given for the properties of crystals to operate at 200°C. The characteristics of an AT type crystal have been investigated experimentally, and the measured results are in reasonable agreement with the calculations. It is shown that there is a maximum temperature of 190°C for which an AT type crystal can have a zero temperature coefficient.