Thermal expansion of the C15 Laves-phase materials TaV₂ and TaV₂H_x

Abstract

The thermal expansion of the C15 Laves-phase material TaV₂H _x was measured over the temperature range of 130–350 K for x = 0, 0.34 and 0.53. A primary objective of the study was to see if the anomalous temperature dependence of elastic constants found in an earlier study is due to, or associated with, unusual thermal expansion. The expansion was typical of transition metals, and quite close to theoretical results for related Laves-phase materials. Grüneisen parameters were determined from the measurements, and these were also typical of transition metals, and close to calculated values for related materials. Both the thermal expansion and the Grüneisen parameters of TaV₂ decreased somewhat with the addition of hydrogen. No anomalous behavior of the expansion was found that might account for the highly anomalous temperature dependence of elastic moduli reported earlier. This absence is consistent with the attribution of the elastic constant behavior to an electronic structure effect.

Acknowledgements

The work at Colorado State University was supported by a grant from the US National Science Foundation under grant DMR-0070808. The work at the Institute of Metal Physics in Ekaterinburg was partially supported by the Russian Foundation for Basic Research (grant 03-02-16063).