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

作者：Jacob K T^*; Sharma Juhi; Gupta Preeti

来源：Journal of Phase Equilibria and Diffusion, 2012, 33(6): 429-436.

DOI：10.1007/s11669-012-0110-4

• electromotive force (EMF)
• enthalpy of formation
• entropy
• Gibbs energy
• isothermal section
• phase equilibria
• thermodynamic properties

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; %26lt;br%26gt;Delta G(f)degrees((ox)) (+/- 78)/(J/mol) = -50535 + 3.85(T/K) %26lt;br%26gt;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%26apos;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.

• 出版日期2012-12