THERMAL-ANALYSIS OF CHEMICAL-REACTION FORMING THE CUGASE2 SINGLE-PHASE

The chemical reaction which forms the CuGaSe2 phase has been investiga ted by differential thermal analysis and powder X-ray diffraction. The two mixtures of CuGa+2Se and Cu+Ga+2Se are used as starting materials . In the former mixture, the CuGaSe2 phase has been formed incompletel y below the melting point of CuGaSe2. In the latter mixture, the CuGaS e2 phase has been formed by the exothermic reaction between CuSe2 and Ga phases at about 900 degrees C, after the formation of the CuSe2 pha se below 380 degrees C. In contrast to the case of CuInSe2, the seleni zation of CuGa alloy is not necessarily required for growing the CuGaS e2 single phase. The chemical reaction between Cu selenides and Ga at temperatures higher than 900 degrees C works to remove heterogeneous p roducts and form a CuGaSe2 single phase.