A structural study on the CuGaSe2‐related copper‐poor materials CuGa3Se5 and CuGa5Se8: thin‐film vs. bulk material

Polycrystalline samples of CuGaSe 2 -related defect compounds (DC) have been prepared by Chemical Close-Spaced Vapour Transport (CCSVT) (thin films) and elemental synthesis (powder) respectively. In the latter case a homogenisation step was introduced during the preparation, including mechanical intermixing and adjacent-heat treatment after the main reaction. Following this route we assured conditions "close to" thermodynamic equilibrium. The influence of the annealing temperature on the lattice parameters a 0 and c 0 , as well as the cation distribution, was investigated. By means of X-ray and neutron diffraction analysis the structural properties of the Cu―Ga―Se based DCs have been determined and a new structural model has been derived. Finally the structural parameters of CCSVT-grown thin-film material were correlated with findings for bulk material samples which were intentionally prepared off-equilibrium.