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Oxygen Potentials for the Oxidation of Rare Earth Oxysulfides to Oxysulfates

Jacob, KT and Akila, R and Shukla, AK (1987) Oxygen Potentials for the Oxidation of Rare Earth Oxysulfides to Oxysulfates. In: Journal of Solid State Chemistry, 69 (1). pp. 109-115.

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Abstract

The equilibrium oxygen potentials corresponding to the oxidation of rare earth oxysulfides to their respective oxysulfates are measured in the temperature range 900 to 1480 K using the solid-state cell Pt, Ni + $NiO/(CaO)Zr0_2/R_20_2S + R_20_2S0_4$, Pt, where R = La, Pr, Nd, Sm, Eu, Gd, Tb, or Dy. The reference electrode consisting of a mixture of Ni + NiO is selected as its oxygen potential lies close to those of the rare earth systems studied here. At a constant temperature, the oxygen potentials for the oxidation of the oxysulfides to oxysulfates are found to increase monotonically with the atomic number of the rare earth element. The “second law” enthalpy change for the oxidation reaction also shows a similar trend, albeit a larger uncertainty. Based on the empirical trend, the changes in the standard Gibbs’ energy accompanying the conversion of oxysulfides of Ho, Er, and Tm to their oxysulfates are estimated. The higher polarizing powers of the heavier trivalent rare earth ions appear to destabilize the relatively open structure oxysulfates more than the close-packed oxysulfides.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier Science.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 24 Jun 2008
Last Modified: 19 Sep 2010 04:45
URI: http://eprints.iisc.ernet.in/id/eprint/14330

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