A new silicon-doped cation-deficient thiospinel, Cu5.52(8)Si1.04(8)square 1.44Fe4Sn12S32: Crystal structure, Mossbauer studies, and electrical properties

Starting from pure metals and sulfur in evacuated silica tubes, single crys tals of Cu(5.522(8))Si(1.04(8))square 1.44Fe4Sn12S32 have been obtained by quenching from 680 degreesC. The above cation-deficient thiospinel crystall izes in the Fd (3) over barm space group with a = 10.3322(6) Angstrom. Si d oping leads to additional vacancies in the copper site. Sn-119 Mossbauer da ta show the presence of Sn in II as well as IV oxidation states and all the Sri is present in the octahedral 16d sites. Fe-57 Mossbauer studies show F e to be present in the octahedral sites in both II and III oxidation states . The above thiospinel shows semiconducting behavior with resistivity of si milar to1 x 10(2) Ohm -cm at room temperature and a small band gap of simil ar to0.1 eV. (C) 2001 Academic Press.