Synthesis of binary and multinary metal sulphides by precipitation and their characterisation

Abstract CuS, In 2 S 3 , CuInS 2 and CuGaS 2 semiconductors have been synthesised in powder form by precipitation reaction using Na 2 S·3H 2 O as a precipitating agent. Precipitated at about 313 K in aqueous medium, the powders of CuS crystallise in covellite (hexagonal) phase and those of In 2 S 3 , CuInS 2 and CuGaS 2 in tetragonal phase on heat treatment in argon atmosphere. The formation of CuS or In 2 S 3 takes place due to the reaction between the metal and bisulphide ions in aqueous phase while that of CuInS 2 or CuGaS 2 involves solid state reaction between CuS and In 2 S 3 or Ga x S y during heat treatment and is accompanied with the evolution of SO 2 gas. The powders are nearly monophasic, exhibit nanometric morphology and bear their respective stoichiometric compositions. The direct band gaps of CuS, In 2 S 3 , CuInS 2 and CuGaS 2 measure 2.06, 2.3, 1.34 and 2.38 eV respectively. The method is simple and is extended to the synthesis of CuIn 0.8 Ga 0.2 S 2 as well.