Phase Diagram of (CuInSe2)1−x(FeSe)x alloys

Polycrystalline samples of the (CuInSe2)1−x(FeSe)x alloy system in the composition range 0 ⩽ x ⩽ 1 were prepared by the melt and anneal technique. X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA) techniques were used to characterize the products. From the analysis of the experimental results a T-x phase diagram was proposed. It was found that at 600 K, two single phase fields (chalcopyrite and a semi-ordered phase in space group P4¯2c) were separated by a relative narrow two phase field in the composition range 0 < x < 0.4. For higher values of x, a secondary phase identified as γ-Fe7Se8 coexist with the semi-ordered phase for 0.4 < x < 0.7 and with a stannite phase for 0.7 < x < 0.95. The variation with composition of the order-disorder phase transition was well described by an extension of Van Vechten theory.