SCANDIUM SULFIDE

Preparation

Scandium(III) sulfide, Sc2S3, is a yellow solid. Metal sulfides are typically prepared by heating mixtures of the two elements, but in the case of scandium, this method results in the formation of scandium monosulfide, ScS. Sc2S3 can be produced by heating scandium(III) oxide under flowing hydrogen sulfide in a graphite crucible to 1550℃ or higher for 2-3 hours. The crude product is subsequently purified by chemical vapor transport at 950℃  utilizing iodine as the transport agent.
Sc2O3+3H2S→Sc2S3 +3H2O

Structure and conformation

The crystal structure of Sc2S3 is similar to that of sodium chloride, in that it is based on a cubic close-packed array of anions. While NaCl has all the octahedral interstices in the anion lattice occupied by cations, Sc2S3 has one-third of them vacant. The vacancies are ordered, but in a very complicated pattern, resulting in a large, orthorhombic unit cell belonging to the space group Fddd. Above 1100℃, Sc2S3 loses sulfur, resulting in nonstoichiometric compounds such as Sc1.37S2.