The second-order pressure derivatives of the elastic moduli of a machinable glass ceramic

The second-order pressure derivatives of the elastic moduli of a machinable glass ceramic have been determined. The latter were evaluated from the change in the velocity of longitudinal and shear sound waves over a pressure range of 0–2 GPa. The two second-order pressure derivatives are both negative, analogous to the behavior of crystalline solids. From the pressure derivatives, the first- and second-order Murnaghan equations of state were calculated, as well as the volume derivatives of the Grüneisen gammas and Grüneisen constant. The latter values are appreciably higher than those of crystalline solids, but of the same order as those of fused quartz.