Temperature dependence of the ultrasonic nonlinearity parameters of NaCl

Abstract

The ultrasonic harmonic generation technique using a capacitive detector has been used to measure the ultrasonic nonlinearity parameters of sodium chloride single crystals between 300 and 77 K. Since NaCl is a typical ionic crystal, its ordinary elastic constants have been of interest to many physicists. Likewise, its nonlinear properties, its third‐order elastic constants, and their temperature dependence have been of interest to solid‐state theory. However, to date the large thermal expansion coefficient and the fragility of NaCl have thwarted measurement of the temperature dependence of its nonlinearity parameters. Differential expansion between NaCl and a bonded quartz transducer often has resulted in sample cleavage. A special technique for bonding the quartz transducer to the NaCl sample has been developed. With the aid of this technique, ultrasonic nonlinearity parameters of three different oriented samples of NaCl have been measured for the first time in the temperature ranges of 300 to 77 K for the (100) sample, 300 to 100 K for the (110) sample, and 300 to 110 K for the (111) sample. The TOE constant C111 and two combinations of the other TOE constants and their temperature dependence have been obtained. The results are compared with theory describing interatomic forces in alkali halide crystals. (Research supported in part by the ONR and the UT‐ORNL Science Alliance.]