Structural studies at high pressure of the ternary family Cu In (S, Se, Te)2

The ternary compounds CuInS2, CuInSe2, and CuInTe2 crystalize in the chalcopyrite structure with spatial group I42d. They have been widely studied in normal conditions because of their possible applications in optpelectronics industry, in non-linear optics, and solar cells. These materials under high pressure have been poorly studied, and it is rare to find the state equation V(P), that it has not been determined. In this work we present the structural studies of these materials cariied out until 30 GPa, using a diamond-anvil cell. The structure was determined by X-ray diffraction in energy dispersion with radiation of synchrotron, the volume variation as a function of the temperature was obtained in that range. In these compounds we observed a single phase transition in the pressure range studied , at 9.5 7.6, and 5.9 GPa for CuInS2, CuInSe2, and CuInTe2, respectively. The 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 dependence with respect to the pressure for unitary formula has been fitted with the first order Murnaghan's equation, for the calculation of bulk modulii. We observed a bulk modulii decreasing by the anionic substitution S → Se → Te. 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 present the V(P) equation of these ternary compounds, the bulk modulii and their changes due to the anionic substitution. We are going to discuss also the structural reversibility when the pressure ended. (Author)