High pressure phase transformations and superconductivity in the Ti-H system

It is shown that the composition of the high-pressure phase formed in TiHx at P> or approx.20.5 kbar (a quadruple point) is x ≅ 0.7. The T-x diagram of the Ti-H system is featured at pressures somewhat above the quadruple point. An inverse isotope effect is stated for the superconducting ε-phase: Tc=4.3 K in TiHx and Tc=5.0 K in TiDx. The ε to δ transformation is studied by Tc and resistivity measurements. Small-angle neutron scattering confirms the composition of the δ-phase, x=1.0. The grain structure of excessive Ti precipitating at the ε to δ transformation depends on the rate of heating of the ε-TiH(D)x, from α-phase to nearly amorphous fractal aggregations. (orig.)