The effect of isotopic substitution on the critical temperature of the niobium-hydrogen system

The critical temperatures for the alpha - alpha ' transition for niobium-hydrogen and niobium-deuterium have been determined as 450 and 430K, respectively. These values were obtained from an analysis of pressure-composition-temperature data above Tc from this research. The result that TcH>TcD for the niobium-hydrogen system is similar to the effect found for isotopic substitution on the critical temperatures in the palladium-hydrogen system.