Some Solid Solutions of the Rare Earth Sulfides in Strontium Sulfide

The nature of various solutions of rare earth sulfides in strontium sulfide has been investigated. The procedure used depended essentially upon the precision determination of the lattice constants of the solutions. , , , , , and were prepared by heating the respective anhydrous chlorides in at elevated temperatures. Solutions of each were made up by intimately grinding weighed amounts of the rare earth sulfide, strontium sulfide, and a lithium fluoride flux and firing the mixtures for one hour in a stream of at a temperature of 1000 C. The results of the lattice constant determinations on these solutions showed that all the rare earth sulfides studied are appreciably soluble in strontium sulfide. (The anomalously high solubilities of and cannot, at present, be explained.) The data also indicate that the rare earth ions in solution remain in the trivalent state. It was also shown that the solutions are substitutional in nature, two rare earth ions replacing three strontium ions in the lattice. This substitution leads to the formation of holes in the cation lattice thus making the solutions defect structures.