System Ho-Rh-O: Phase Equilibria, Chemical Potentials and Gibbs Energy of Formation of HoRhO3

Jacob, KT and Sharma, Juhi and Gupta, Preeti (2012) System Ho-Rh-O: Phase Equilibria, Chemical Potentials and Gibbs Energy of Formation of HoRhO3. In: JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION, 33 (6). pp. 429-436.

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Abstract

The thermodynamic properties of the HoRhO3 were determined in the temperature range from 900 to 1300 K by using a solid-state electrochemical cell incorporating calcia-stabilized zirconia as the electrolyte. The standard Gibbs free energy of formation of orthorhombic perovskite HoRhO3, from Ho2O3 with C-rare earth structure and Rh2O3 with orthorhombic structure, can be expressed by the equation; Delta G(f)degrees((ox)) (+/- 78)/(J/mol) = -50535 + 3.85(T/K) Using the thermodynamic data of HoRhO3 and auxiliary data for binary oxides from the literature, the phase relations in the Ho-Rh-O system were computed at 1273 K. Thermodynamic data for intermetallic phases in the binary Ho-Rh were estimated from experimental enthalpy of formation for three compositions from the literature and Miedema's model, consistent with the phase diagram. The oxygen potential-composition diagram and three-dimensional chemical potential diagram at 1273 K, and temperature-composition diagrams at constant oxygen partial pressures were computed for the system Ho-Rh-O. The decomposition temperature of HoRhO3 is 1717(+/- 2) K in pure O-2 and 1610(+/- 2) K in air at a total pressure p(o) = 0.1 MPa.

Item Type:	Journal Article
Publication:	JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION
Publisher:	SPRINGER
Additional Information:	Copyright for this article belongs to Springer
Keywords:	electromotive force (EMF); enthalpy of formation; entropy; Gibbs energy; isothermal section; phase equilibria; thermodynamic properties
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	21 Dec 2012 04:07
Last Modified:	21 Dec 2012 04:07
URI:	http://eprints.iisc.ac.in/id/eprint/45538

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