Elastic constants of cubic lead fluoride from 300 to 850 K

Abstract

Measurements of ultrasonic velocity in single-crystal cubic ${\mathrm{PbF}}_{2}$ have been made over a temperature range from 300 to 850 K. Values of the three independent, adiabatic elastic constants over this temperature range are obtained from ${C}_{11}$, $\frac{({C}_{11}+{C}_{12}+{2C}_{44})}{2}$, $\frac{({C}_{11}\ensuremath{-}{C}_{12})}{2}$, and ${C}_{44}$. The results are anomalous at the Faraday temperature of 711 K for ${\mathrm{PbF}}_{2}$, which is well below its melting temperature of 1158 K. A large decrease in the elastic constant ${C}_{11}$ and much smaller decrease in ${C}_{12}$ and ${C}_{44}$ are observed near 711 K in addition to the nearly linear decrease in the elastic constants with temperature.