Preparation and characterization of (CuInSe2)1-x(CoSe)x alloys in the composition range 0 x 2/3.

Polycrystalline samples of (CuInSe2)1-x(CoSe)x alloys were prepared by the normal melt and anneal technique in the composition range 0 < x 2/3. The obtained ingots were characterized by scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. A sample with x = 2/3 (prepared a posteriori) was also studied by the Raman shift technique. The results showed a complex behavior of the phase diagram. The phase () with chalcopyrite structure exists in a narrow interval 0 < x < 0.1 in the composition range; then, for 0.1 < x < 0.25, the ordered phase gradually transforms into a disordered () phase where the cation sites are multi-occupied (Cu, Co and In) at random. For 0.25 < x < 0.35, two phases were observed, the phase and another, not identified () phase. Finally, for 0.35 < x < 2/3, another chalcopyrite-like phase () was observed together with traces of the phase. The sequence of phase transformations in the studied composition range seems to be alpha alpha' alpha'+Y alpha''+Y