Thermal Stability of Metal Hydrides, Deuterides and Tritides

INTEREST in the stability of metal hydride materials has been stimulated by their potential use as reactor moderators and as target materials in neutron generating devices which could find widespread application in compact activation analysis equipment. Earlier work has scanned the thermal stability of most rare earth and yttrium dihydrides and dideuterides1–6, and the effects of varying the rare earth metal on the heats and entropies of formation have been discussed in terms of lattice energies and parameters2. The differences from one author to another are quite large in many instances; accordingly, when we decided to determine the thermal stability of a rare earth tritide a method involving measurements of the isotopic separation in a mixed deuterium–tritium system was preferred. Erbium metal was chosen as suitable in view of its cheapness and comparatively high oxidation resistance7. Titanium and uranium systems were also investigated, the former because of its common use in targets and the absence of good data on deuteride stability, and the latter because of the availability of dissociation pressure data for comparison.