Samarium(III) sulfide
Samarium sulfide is a chemical compound of the rare earth element samarium, and sulfur. In this compound samarium is in the +3 oxidation state, and sulfur is an anion in the −2 state.
Synthesis
Samarium sulfide can be produced by treating metallic samarium with sulfur:Once prepared, samarium sulfide can be purified by chemical vapor transport using iodine.
Samarium sulfide can also be prepared by treating the sulfate with hydrogen sulfide at elevated temperatures:
Properties
The low temperature α form crystallises in the orthorhombic crystal system. The unit cell has dimensions a=7.376, b=3.9622 c=15.352 Å with volume 448.7 Å3. There are four of the formula in each unit cell. The density comes out to 5.88 kg/liter. There are two kinds of samarium coordination in the solid, one is eight coordinated with sulfur surrounding in a bicapped trigonal pyramid. The other is a sevenfold capped distorted octahedral arrangement. This structure is similar to other light rare-earth element sulfides.Samarium sulfide is a semiconductor with a band gap of 1.7 eV. As a thin film on high area electrodes, it is under investigation as a super capacitor dielectric, with specific capacitances of up to 360 Farads per gram.