Urania-neodymia compositions were sintered in air and in hydrogen. The compositions were studied by chemical, x ray, and differential thermal analyses. Solid solutions formed readily in air-sintered compositions in the range from 20 to 60 m/o Nd/sub 2/O/sub 3/. Solid solutions formed slowly and incompletely, up to 1650 deg C, in hydrogen-sintered compositions. There was good correlation between the differential thermal analyses and the chemical and x ray analyses. (auth)