Phase equilibria and thermodynamics of the double oxide phase Cu3TiO4 |
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Authors: | D Hennings |
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Institution: | Philips GmbH Forschungslaboratorium Aachen, 5100 Aachen, Federal Republic of Germany |
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Abstract: | Phase equilibria in the system CuCu2OTiO2 were investigated in the temperature range of 1160–1270 K by means of thermogravimetry and measurements of the oxygen partial pressure. The tie lines on the isothermal phase diagram run from the phase Cu3TiO4 to CuO, Cu2O, and TiO2. The existence of Cu3TiO5 and Cu2TiO3 could not be confirmed in this temperature range. The phase “Cu3TiO4” is only stable above about 1140 K and its composition fluctuates between about Cu3TiO4.3 and Cu3TiO3.9. The formation of Cu3TiO4.3 according to the reaction 1.6 CuO + 0.7 Cu2O + TiO2 = Cu3TiO4.3 is endothermic: (1160 < T < 1270 K) ΔH° = (7600 ± 450 J-mole?1; ΔS° = (6.7 ± 0.4) J·K?1·mole?1. The standard Gibbs free energy, enthalpy, and entropy of formation of Cu3TiO4.3 at 1200 K are ΔG°f = ?101.39 kJ, ΔH°f = ?1115.84 kJ, and S°f = 466.76 J·K?1. Rather similar values were found for Cu3TiO3.9. |
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