Sintering Characteristics and Properties of PuS and PuP

The compounds PuS and PuP were prepared by high‐temperature homogenization of the product from the reaction of H 2 S or PH 3 gas with partly decomposed plutonium hydride. Studies of sintering characteristics of pellets fired in vacuum and in an argon atmosphere showed that these materials can be sintered to densities slightly greater than 90% of theoretical. The sintering process appears to be complex due to changes of mechanism with increasing temperature. Weight loss data indicate that PuP has a higher effective vapor pressure than PuS but under conditions of fuel irradiation (1 atm pressure of inert gas) PuP has a much lower rate of vaporization. Microstructural examinations and lattice constant measurements verify that monosulfide and monophosphide can exist as substoichiometric compounds. Curvature of the sulfur‐rich phase boundary toward greater sulfur solubility at high temperatures is indicated from the X‐ray data. Density, melting point, thermal expansion, microhardness, Seebeck coefficient, electrical resistivity, thermal diffusivity, heat capacity, and thermal conductivity are reported.