Thermodynamics of CuInO ₂ Preparation by Cation Exchange Reaction

Abstract To investigate the optimum conditions of the CuInO ₂ (CIO) preparation by cation exchange reaction method, the standard entropy, thermal capacity at constant pressure, standard enthalpy and standard Gibbs free energy of formation were estimated. The relations of temperature ( T ) and thermodynamic equilibrium constants ( K ), the conditions for three independent reactions were analyzed in CuInO ₂ preparation. The curves of Gibbs free energy- T , K − T and P _CuCl − T for those reactions have been plotted. The results showed that the CIO powder could be synthesized by cation exchange reaction. There were two main reactions through the way of NaInO ₂ reacting with CuCl. One was NaInO _2(s) reacting with CuCl _(s) at T ≥ 1698 K. The cost was higher in the way. The other was NaInO _2(s) reacting with CuCl _(g) at T < 1698 K. However, the yield of CIO would be decreased because CuInO ₂ powder decomposed into Cu ₂ O _(s) and In ₂ O _3(s) with the temperature reduced, especially when T ≤ 573 K. And the higher vapor pressure of CuCl _(g) was necessary for the process, which needs the higher temperature since the vapor pressure of CuCl _(g) increases with increasing temperature, especially when T > 973 K. It was recommended that NaInO _2(s) react with CuCl _(g) for preparing CIO under conditions of 973 < T ≤ 1698 K and the vacuum in the reactor.