Solid-phase growth of CuGaS2 crystals

Homogenized mixtures of copper, gallium, and sulphur were annealed for 200 hrs. under vacuum at about 1000–1050°C (i.e. below the melting point of the CuGaS₂ phase) in quartz ampoules in a vertical position, and then cooled down in a temperature gradient. The final charge was made up of three well-defined portions: a yellow polycrystalline CuGaS₂ with large blocks of CuGaS₂ (close to stoichiometry), a black portion with darkgreen aggregates of small CuGaS₂ crystals, and yellow laminae of CuGaS₂ single crystals, slightly inclined away from [112] direction. — A coupled growth mechanism — solidstate-diffusion-assisted coalescence/vapour transport — is assumed.