Elastic constants ofV2O3between 300 and 640 K: Anomalies near the high-temperature electrical transition

The elastic stiffness moduli of ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ are determined between 300 and 640 K from measurements of the travel times of 30- and 150-MHz ultrasonic waves. Unusual behavior is found. Elastic constants $C_{11}$, $C_{12}$, and the bulk modulus each go through a deep minimum at 540 K in the region of the high-temperature electrical transition. Some modes soften drastically between 300 and 540 K and then less strongly at higher temperatures. Two shear modes stiffen monotonically with temperature. $C_{44}$ is observed to increase very slightly with temperature near room temperature, go through a maximum, and then pass through a minimum near 540 K. These results are discussed in the context of the high- and low-temperature electrical transitions in ${\mathrm{V}}_2$ ${\mathrm{O}}_3$.