SOME COMBINATIONS OF THIRD-ORDER ELASTIC CONSTANTS FOR STRONTIUM TITANATE SINGLE CRYSTALS

Three linear combinations of the six adiabatic third-order elastic constants in cubic crystals can be determined by use of the ultrasonic second-harmonic generation technique. The combinations which are obtained are designated K3[100], K3[110], and K3[111]. In the work reported here, room-temperature values of the K3's have been measured for strontium titanate single crystals. The reported values are (in units of 1012 dyn/cm2): K3[100]=C 111=-49.6±4.3 K3[110]=14(C111+3C 112+12C166=-27.3±3.2 K3[111]=19(C 111+6C112+12C144+24C166+2C 123+16C456=-27.9±2.6. The data have been compared with the theoretical values of K3 for the alkali halide crystals, and it has been observed that the ratio of | C111 |/C11 for strontium titanate agrees with the corresponding ratio for many of the NaCl type crystals. In order to estimate the six third-order elastic constants of strontium titanate, it has been assumed that the Cauchy relations extended to third-order elastic constants hold. © 1969 The American Institute of Physics.