Thermal Conductivity and Heat Capacity of the Monophosphide and Monosulfide of Plutonium

The thermal properties of PUP and PUS were measured from room temperature to 650° C by a heat‐pulse technique. Disk‐shaped specimens of 90% theoretical density were made by isostatic cold‐pressing and sintering. The thermal conductivity of PUP corrected to theoretical density ranged from 0.014 cal sec ‐ cm ‐1 °C ‐1 at room temperature to 0.019 at 650° C. Over this temperature range the heat capacity increased from 0.055 to 0.056 cal g ‐l °C ‐1 . The thermal conductivity of PUS decreased approximately 16% from its room temperature value of 0.023 cal sec ‐ cm ‐1 °C ‐1 and then rose to 0.037 at 650°C. The temperature dependence of the thermal conductivity of PUP is apparently related to the quasimetallic electrical properties of this compound. PUS is a semiconductor and the rise in its thermal conductivity (after passing through a minimum) may be partly attributed to a bipolar thermal diffusion mechanism.