Generalized Gruneisen parameters of elastic waves and the low-temperature thermal expansion of alumina from its third-order elastic-constant data

The generalized Gruneisen parameters (GP's) of elastic waves propagating in different directions in Al2O3 are calculated from the measured second- and third-order elastic constants. These GP's in alumina are found to have small but positive values. The Brugger gammas are evaluated and the low- temperature limit of the Gruneisen gamma is calculated using the procedure of Ramji Rao and Srinivasan. GammaL has the value 1.37, indicating that the thermal expansion of alumina is positive down to 0 K. 13 ref.--AA.