Temperature dependence of the elastic shear modulus of the Laves-phase materials TaV 2 and TaV 2H x

Abstract

Resonant ultrasound spectroscopy has been used to measure the shear modulus of polycrystalline TaV 2H x for x=0, 0.06, 0.10, 0.18, 0.34, and 0.53 over the temperature range of 20–300 K. The results show a strong influence of hydrogen on both the magnitude and the temperature dependence of the shear modulus of these materials. These results are in qualitative agreement with a model involving the electronic structure of these C15 Laves-phase materials. The symmetry of the C15 structure results in doubly-degenerate electronic energy levels at the X point of the Brillouin zone. These levels couple to the shear strain e 4 with resulting effects on the single-crystal elastic constant c 44. The strong temperature and concentration dependence of c 44 contributes to the measured shear moduli of these polycrystalline materials.