Properties of synthetic quartz oscillator crystals

A process for the growing of quartz crystals artificially is briefly described. This so-called synthetic quartz, which is being grown reproducibly as well-formed crystals weighing about 135 grammes, possesses electrical and mechanical properties which closely follow those of the natural Brazilian quartz commonly used for piezo-electric purposes. The high overall quality of synthetic quartz, its freedom from twinning and other faults and its regular shape and size make it a convenient material to handle with the minimum of wastage. Measurements have been carried out to compare the properties of oscillator crystals cut from natural and synthetic quartz. The behaviour of the AT- and BT-cuts has been investigated thoroughly, while some results have also been obtained on units of the CT-, DT-and 5° X-cuts. Most of the parameters measured show no appreciable difference between the values for natural and synthetic quartz. Two notable exceptions are a small difference in the frequency/temperature characteristics of AT-cut units, whether operated at fundamental or at overtone frequencies, and an apparently reduced activity of face-shearmode units of the CT-and DT-cuts from the synthetic material. The significance of these results is discussed, together with the possibility of more accurate measurements to compare the intrinsic mechanical losses in natural and synthetic quartz.