The thermodynamics and phase behaviour of Tb2Pd2O5 and Er2Pd2O5

Jacob, Thomas K and Lwin, Kay Thi and Waseda, Yoshio (2002) The thermodynamics and phase behaviour of Tb2Pd2O5 and Er2Pd2O5. In: Journal of Chemical Thermodynamics, The, 34 (10). pp. 1509-1529.

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Abstract

Isothermal sections of the phase diagrams for the systems Ln-Pd-O (with Ln = Tb or Er) have been established by equilibration of samples at T = 1223 K, and phase identification after quenching by optical and scanning electron microscopy (OM, SEM), energy dispersive spectroscopy (EDS), and X-ray powder diffraction (XRPD). Two oxide phases were stable along the binary Tb-O: Tb2O3+x, a phase of variable composition, and Tb7O12 at T = 1223K. The oxide PdO was not stable at this temperature. Only one ternary oxide Tb2Pd2O5 was identified in the Tb-Pd-O system. No ternary compound was found in the system Er-Pd-O at T = 1223K. However, the compound Er2Pd2O5 could be synthesized at T = 1075 K by the hydrothermal route. In both systems, the alloys and inter-metallic compounds were all found to be in equilibrium with the lanthanide sesquioxide Ln(2)O(3) (where Ln is either Tb or Er). Two solid-state cells, each incorporating a buffer electrode, were designed to measure the Gibbs energy of formation of the ternary oxides, using yttria-stabilized zirconia as the solid electrolyte and pure oxygen gas as the reference electrode. Electromotive force measurements were conducted in the temperature range (900-1275) K for Th-Pd-O system, and at temperatures from (900-1075) K for the system Er-Pd-O. The standard Gibbs energy of formation Delta(f)G(m)degrees,, of the inter-oxide compounds from their component binary oxides Ln(2)O(3) and PdO are represented by equations linear in temperature. Isothermal chemical potential diagrams for the systems Ln-Pd-O (with Ln = Tb or Er) are developed based on the thermodynamic information. (C) 2002 Elsevier Science Ltd. All rights reserved.

Item Type:	Journal Article
Publication:	Journal of Chemical Thermodynamics, The
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	phase diagrams;systems Tb–Pd–O and Er–Pd–O;thermodynamic properties of Tb2Pd2O5 and Er2Pd2O5
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	27 Jul 2011 09:43
Last Modified:	27 Jul 2011 09:43
URI:	http://eprints.iisc.ac.in/id/eprint/39496

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