Elastic properties of the Ta–V system: bcc Ta_0.33V_0.67 and C15 TaV₂

Abstract

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300 K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295 K for the C15 phase and 315 K for the bcc phase.

Acknowledgements

The work at Colorado State University was supported by 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 06-02-16246).