Abstract :
It has been reported that synthetic quartz can be unlike natural quartz with regard to its behaviour as a mechanical resonator. In particular, differences may be observed in the frequency/temperature characteristics and Q-factor of AT-cut synthetic-crystal units. These derive from imperfections in the quartz structure, the concentrations of which are known to depend critically upon certain physical-chemical growth conditions. Recently it has been demonstrated that the electrolysis of synthetic quartz results in the effective elimination of those imperfections which, in terms of the acoustic behaviour of synthetic quartz, sets it apart from the natural material. Specifically, the so-called 50° K and 300° K defects are removed, the latter defect being common to fast-grown Z-growth quartz (material grown on a seed surface oriented perpendicular to the Z-axis). Beyond this, however, electrolysis is found to effect a unique improvement in the performance of synthetic and natural quartz at high temperatures. The Q-factor of an AT-cut resonator operating at 500° C is reported to be 5 × 105, representing an improvement of at least two decades above previously recorded values. An analysis of these results is given, together with a discussion of the significance of this discovery in relation to frequency control.
