Piezoelectric and Mechanical Behavior of X-Cut Quartz Shock Loaded at 79°K

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Abstract
The piezoelectric and mechanical behavior at 79°K of uniaxially strained X‐cut quartz has been experimentally investigated by an impact technique for stresses ranging between 6 and 21 kbar. Knowledge of this behavior is necessary to extend to liquid nitrogen temperature the use of large diameter‐to‐thickness ratio X‐cut quartz disks as submicrosecond gauges for observing stress‐time profiles induced in materials by plane wave shock loading. For stresses up to at least 21 kbar, elastic behavior is observed. The elastic wave velocity and mechanical impedance have constant values of 5.72 mm/μsec and 152 kbar/mm/(mm/μsec), respectively, which are within ±1% of 298°K values. From a least squares fit to the data, the piezoelectric factor at 79°K relating current and stress in uniaxial strain depends on stress σx and is given by (2.11×10−8+5.5×10−11σx) C/(cm2‐kbar), as compared to (2.01×10−8+1.1×10−10σx) at 298°K. These expressions are based on 298°K values of the electrode area and thickness of the quartz disk. In the limit of zero stress, there is reasonable agreement between the e11/c11 piezoelectric coefficient determined from the 79°K expression and that obtained from low signal resonance measurements. A small apparent increase in the dielectric permittivity with stress is observed at 79°K.