The phase relations in the system Cu,In,Se

The phase relations in the system Cu,In,Se are evaluated by DTA and direct observations of the solid-liquid equilibria in the temperature range 800 ≤ T ≤ 1300 K. Five distinct miscibility gap regions where two liquids coexist in equilibrium with a solid phase are observed. Four of these regions extend from monotectics on the Cu-Se and In-Se binaries into the ternary field and tie to the homogeneity ranges about Cu2Se, In2Se3 and In4Se3, respectively. The fifth miscibility gap regions ties to the homogeneity range about CuInSe2 at ∼ 943 K. Further clarification concerning the phase relations on the Cu2Se-In2Se3 pseudobinary is presented for the Cu2Se-rich section where four temperature invariant 3-phase lines are observed. In addition to the γ-δ transition a second solid state transformation δ-ζ exists for stoichiometric CuInSe2 in the disordered high temperature phase. A correction of the previously published phase relations at XIn2Se3 < 0.2 is needed because of reactive interactions of the melt with unprotected fused silica enclosures used in the earlier work. The position of the second congruently melting ternary compound C on the Cu2Se-CuInSe2 cut is slightly shifted from the previously reported composition Cu5InSe4 to Cu18In4Se15, and the existence of an additional compound P is suggested that we tentatively link to a peritectic reaction at 1258 K between liquid at x = 0.105 and saturated solid solution of In2Se3 in Cu2Se referred to as α-phase. A eutectic exists between P and C at 1208 K.