The thermodynamic stability of the chalcopyrite CuGaSe2 compound semiconductor was studied. Asolid-state electrochemical cell was employed to obtain the standard Gibbs energy of formation ofCuGaSe2. The reversible EMF data of the following cell over the range of 818 to 950 K were measured:Pt, Ga(l), Ga2O3(s) // 15 YSZ // Ga2O3(s), Cu2Se(s), CuGaSe2(s), Cu, C, Pt. By using Cu2Se literaturedata with the EMF results, the following expression for the standard Gibbs energy of formation forCuGaSe2 was obtained: (DGof CuGaSe2) (kJ/mol) = -233.31 + 0.0075T(K) (818 to 950 K). The calculatedDGof function shows that the ternary CuGaSe2 compound is more stable than the corresponding CuInSe2by approximately 10 kJ/mol over the entire temperature range of the present investigation, which isconsistent with the current phase diagram information.
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