Samarium(III) sulfide (Sm<sub>2</sub>S<sub>3</sub>) 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 âÂÂ2 state.
Samarium(III) sulfide can be produced by treating metallic samarium with sulfur:
Once prepared, samarium(III) sulfide can be purified by chemical vapor transport using iodine.
Samarium(III) sulfide can also be prepared by treating the sulfate with hydrogen sulfide at elevated temperatures:
The low temperature ñ form crystallises in the orthorhombic crystal system. The unit cell has dimensions a=7.376, b=3.9622 c=15.352 àwith volume 448.7 à<sub>3</sub>. There are four of the formula in each unit cell (Sm<sub>8</sub>S<sub>12</sub>). 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(III) 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.
Related samarium sulfides include the monosulfide SmS and the mixed valent Sm<sub>3</sub>S<sub>4</sub> which are also semiconductors. KSm<sub>2</sub>CuS<sub>6</sub> is a layered quaternary sulfide.