High-pressure structural analysis of the ternary family CuIn(S,Se,Te)(2)

The ternary compounds CuInSz(2) CuInSe2, and CuInTe2 crystalize in the calc opirita structure with spatial group I (4) over bar 2d. They have been wide ly studied in normal conditions because of their possible applications in o ptoelectronics industry, in non-linear optics, and solar cells. These mater ials under high pressure have been poorly studied, and it is rare to find t he state equation V(P), that it has not been determined. In this work we pr esent the structural studies of these materials carried out until 30 GPa, u sing a diamond-anvil cell. The structure was determined by X-ray diffractio n in energy dispersion with radiation of syncrotron, the volume variation a s a function of the temperature was obtained in that range. In these compou nds we observed a single phase transition in the pressure range studied, at 9.5, 7.6, and 5.9 GPa for CuInS2, CuTnSe(2), and CuInTe2, respectively. Th e phase observed after the transition was indexed as cubic NaCl-type in the three cases, with a volume reduction at transition of 10%. The Volume depe ndence with respect to the pressure for unitary formula has been fitted wit h the first order Murnaghan's equation, for the calculation of bulk moduli. We observed a bulk moduli decreasing by the anionic sustitution S-->Se-->T e. It is a non-reversible process and the recovered phases present changes with respect to the initial phases. For example, the recovered phase after the pressure ended is a totally amorphous phase. In this work we will prese nt the V(P) equation of these ternary compounds, the bulk moduli and their changes due to the anionic substitution. We are going to discuss also the s tructural reversibility when the pressure ended.