Homogeneity range and crystal growth of CuGaSe2

Crystals of CuGaSe2 were grown by chemical vapor transport (CVT) with iodine as transport agent and by horizontal gradient freeze. Using CVT flat crystals of dimensions 50x15x2mm(3) were obtained. CuGaSe2 ingots crystallized from the melt in glassy carbon boats exhibited single crystalline grains of 12x5x5mm(3). Thermo-gravimetric measurements have shown that CuGaSe2 is thermally stable under CVT conditions (Delta T=820-750 degrees C). However, this chalcopyrite thermally decomposes at 1000 degrees C into solid Cu2Se and volatile Ga2Se and Se-2. Therefore, an additional Ga2Se3 source was introduced in the melt growth experiments and hold at 700 degrees C during crystallization. The crystallized ingot exhibited an uniform composition over the whole length. This observation is in contradiction to the established phase diagram proposing a peritectic melting point. Preliminary own differential thermal analyses (DTA) in the join Cu2Se-Ga2Se3 allows the conclusion that CuGaSe2 has a congruent melting point at 1094 degrees C.