Phase stability of Vsub(1-x)Crsub(x)Dsub(0.5) and Vsub(1-x)Tasub(x)Dsub(0.5-x) (x = 0.01-0.10)

The phase stability and structural changes of β-VDsub(0.5) were studied through the substitution of up to 10 at.% Cr or Ta for the vanadium atoms. Heat capacity and neutron diffraction data were used to determine the transformation temperatures and the deuterium occupations of the Vsub(1-x)Crsub(x)Dsub(0.5) and Vsub(1-x)Tasub(x)Dsub(0.5-x) systems as a function of the chromium or tantalum content. An intermediate β2 phase which has an isomorphic structure with β2-VHsub(0.5) appears in Vsub(1-x)Crsub(x)Dsub(0.5) between the low temperature ordered β1 phase and the high temperature disordered α phase. In the Vsub(1-x)Tasub(x)Dsub(0.5-x) system, the occupation of O sites by deuterium becomes unstable with increasing tantalum content. (Auth.)