Crystallization of sulfides from alkali polysulfide fluxes

Alkali polysulfides are solvents suitable for the synthesis of many metal sulfides from the metal and for crystal growth. Crystal plates, ∼ 2 cm diameter, of the antiferromagnetic (below 18 K) semiconductor NaCrS2, and during controlled oxidation, crystals of NaCrO2 and Cr2O3 have been obtained. CdS prepared from sodium polysulfide solution grows in the form of prisms, pyramids or plates depending on the growth temperature (respectively supersaturation) and added impurities. The CdS plates showed a very high dark resistivity and a strong photoconductivity effect. Other sulfides prepared from sodium polysulfide flux include ZnS, PbS, CuS, α-MnS, NiS2, CoS2, FeS2, NaInS2, KFeS2, MoS2, LaS2-x and Cu3VS4. The sodium content of several sulfides varied from 30 to 450 ppm. Attempts to prepare thiospinels like CdCr2S4 from alkali polysulfide solvents have so far failed. © 1974.