Low-Temperature Specific Heat of Palladium Containing Interstitial Hydrogen

Specific-heat measurements in the 1.2 to 4.2°K range have been carried out on four H-Pd specimens having H/Pd atomic ratios of 0.57, 0.70, 0.81, and 0.88. Corresponding values of $\gamma$ (the electronic-specific-heat coefficient) are 2.52, 1.38, 1.40, and 1.61 mJ/${\mathrm{deg}}^2$ per $g$ atom of palladium; values of ${\Theta }_D$ (the Debye temperature) are 282, 273, 276, and 267°K, respectively. A "dynamic" method of measurement was necessarily employed because of the occurrence of an exothermic process in these alloys. The interpretation of the data was complicated by the interstitial character of these alloys, but the present results for the electronic specific heat appear to offer unusually direct support for the usual simple band picture of Pd and H-Pd alloys. Special care must be exercised in the interpretation of the Debye temperatures in this case.