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Gibbs Energy of Formation of Ca3Ti8Al12O37 and Phase Relations and Chemical Potentials in the System Al2O3-TiO2-CaO

Jacob, KT and Rajitha, G (2012) Gibbs Energy of Formation of Ca3Ti8Al12O37 and Phase Relations and Chemical Potentials in the System Al2O3-TiO2-CaO. In: JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, 33 (4). pp. 293-302.

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Official URL: http://dx.doi.org/10.1007/s11669-012-0048-6

Abstract

The quaternary oxide in the system Al2O3-CaO-TiO2 is found to have the composition Ca3Ti8Al12O37 rather than CaTi3Al8O19 as reported in the literature. The standard Gibbs energy of formation of Ca3Ti8Al12O37 from component binary oxides is measured in the temperature range from 900 to 1250 K using a solid-state electrochemical cell incorporating single crystal CaF2 as the solid electrolyte. The results can be represented by the equation: delta G(f(0x))(0) (+/- 70)/J mol(-1) = -248474 - 15.706(T/K). Combining this information with thermodynamic data on calcium aluminates and titanates available in the literature, subsolidus phase relations in the pseudo-ternary system Al2O3-CaO-TiO2 are computed and presented as isothermal sections. The evolution of phase relations with temperature is highlighted. Chemical potential diagrams are computed at 1200 K, showing the stability domains of the various phases in the chemical potential-composition space. In each chemical potential diagram, chemical potential of one component is plotted against the cationic fraction of the other two components. The diagrams are valid at relatively high oxygen potentials where Ti is present in its four-valent state in all the oxide phases.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Springer
Keywords: Ca3Ti8Al12O37; chemical potential diagram; enthalpy of formation; entropy; free energy of formation; isothemal section; phase diagram; system Al2O3-TiO2-CaO
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 10 Sep 2012 12:21
Last Modified: 10 Sep 2012 12:21
URI: http://eprints.iisc.ernet.in/id/eprint/45000

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