| Autor: |
Pokrovski, Gleb S., Diakonov, Igor I., Bénézeth, Pascale, Gurevich, Vyacheslav M., Gavrichev, K?nstantin S., Gorbunov, Vadim E., Dandurand, Jean-L?uis, Schott, Jacques, Khodakovsky, Igor L. |
| Zdroj: |
European Journal of Mineralogy; September 1997, Vol. 9 Issue: 5 p941-952, 12p |
| Abstrakt: |
Abstract The standard molal thermodynamic properties of a-GaOOH at temperatures to 700 K were retrieved from (1) low-temperature a-GaOOH heat capacity measurements, (2) solubility measurements ofa-GaOOH and ß-Ga2O3, and (3) data available for the a-GaOOH - ß-Ga2O3 transformation in the presence of aqueous solution. The heat capacity of a-GaOOH as a function of temperature was found to be consistent with the formulation CP° = 54.38 + 0.06418 T - 11.3 105/T2 (J/mol.K) in the temperature range 298-700 K. The estimated standard molal entropy of a-GaOOH from low-temperature heat capacity measurements is 51.61 ±0.26 J/mol.K. The estimated standard molal Gibbs free energy of formation from the elements for a-GaOOH as retrieved from a-GaOOH and ß-Ga2O3 solubility experiments and available stability data was -627.9 ± 2.0 kJ/mol. The corresponding a-GaOOH standard molal enthalpy of formation from the elements was found to be -705.3 ± 2.5 kJ/mol. These data allowed the prediction of the thermodynamic properties of a-GaOOH to high temperatures and demonstrate that a-GaOOH and ß-Ga2O3 are the stable solid phases in the Ga-O-H system at saturated water vapour pressure below and above 573 K, respectively |
| Databáze: |
Supplemental Index |
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