THERMAL-ANALYSIS OF THE CHEMICAL-REACTION PROCESS FOR CUGA1-XINXSE2 CRYSTALS

We have investigated the chemical-reaction process forming CuGa(1-x)ln (x)Se(2) phases by differential thermal analysis and powder X-ray diff raction. In a Cu + In + Se-2 mixture, the CuInSe2 compound is almost c ompletely formed by exothermic reactions between Cu and In selenides j ust below the melting point of CuInSe2 after the formation of the Cu-S e and In-Se phases below 400 degrees C. In a Cu + Ga + Se-2 mixture, t he CuGaSe2 compound is formed by the exothermic reaction between CuSe2 and Ga at about 900 degrees C, after the formation of the CuSe2 phase below 380 degrees C. In the CuGa1-xInxSe2 solid solution, the melting and transition points show a slightly concave decrease with increasin g composition x. It may be very difficult to lower the number of heter ogeneous phases, because of the difference in the chemical-reaction pr ocesses between end-member compounds.