AGING CHARACTERISTICS OF QUARTZ CRYSTAL RESONATORS
GEORGIA INST OF TECH ATLANTA ENGINEERING EXPERIMENT STATION
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Approximately 140 resonators were mainained in oven storage at 85 C and measured peiodically for frequency and Rs. Of these, approximately 56 were units prepared for long term aging study and the remainder were undergoing measurements preliinary to exposure to high intensity pulsed radition. Thirty new resonators with Al electrodes were fabricated and mounted in the HC- 27U glass container. Heat effects during sealing resulted in major frequency shifts for 12 of these units, from 16 mc to the vicinity of 22 mc, with now signifiant change in Rs. Frequency versus temperatre data and Rs values indicated characteristics resembling an AC-cut more than an At-cut resonator. An investigation of changes in these resonators by the method of X-ray diffraction topography indicated extensive electrical twinning in the units exhibiting the frequency shift. Information concerning strains produced in the quartz by mounting clips and cements could be obtained by X-ray diffraction topogaphy. Aging studies showed many units have high stability, but definite differences in aging rates at the fundamenal and overtone modes of the same unit were observed. Overcoated unts display greater aging rates than units coated only with a base coat.