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# Gibbs Energies of Formation of $CuYO_2$ and $Cu_2Y_2O_5$ and Phase Relations in the System Cu-Y-O

Kale, GM and Jacob, KT (1989) Gibbs Energies of Formation of $CuYO_2$ and $Cu_2Y_2O_5$ and Phase Relations in the System Cu-Y-O. In: Chemistry of Materials, 1 (5). pp. 515-519.

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## Abstract

Thermodynamic properties of cuprous and cupric yttrates $(CuYO_2 and Cu_2Y_2O_5)$ and oxygen potentials corresponding to three three-phase fields in the system Cu-Y-O have been determined by using solid-state galvanic cells; Pt, Cu + $CuYO_2$ + $Y_2O_3$ \parallel $(Y_2O_3)ZrO_2$ \parallel Cu + $Cu_2O$, Pt; Pt, $CuYO_2$ + $Cu_2Y_2O_5$ \parallel $(Y_2O_3)ZrO_2$ \parallel $Cu_2O$ + CuO, Pt; and Pt, $CuYO_2$ + $Cu_2Y_2O_5$ + $Y_2O_3$ \parallel $(Y_2O_3)ZrO_2$ \parallel $Cu_2O$ + CuO, Pt. Yttria-stabilized zirconia was used as the solid electrolyte in the temperature range 873-1323 K. The compound $CuYO_2$ was prepared by the reduction of $Cu_2Y_2O_5$ at 1373 K under argon gas with a residual oxygen partial pressure of \sim 1 Pa. For the reaction $\frac {1} {2} Cu_2O(s) + \frac {1} {2} Y_2O_3(s) \rightarrow CuYO_2(s)$, \Delta G° = -5800 + 3.90T (\pm 30) J $mol^{-1}$, and for $2CuO(s) + Y_2O_3(s) \rightarrow Cu_2Y_2O_5(s)$, \Delta G° = 11 210 - 15.072T (\pm 120) J $mol^{-1}$. The oxygen potentials corresponding to the coexistence of phases $CuYO_2 + Cu_2Y_2O_5$ and $CuYO_2 + Cu_2Y_2O_5 + Y_2O_3$ were found to be the same over the temperature range of measurement, thus indicating negligible solid solubility of $Y_2O_3$ in $CuYO_2$ and $Cu_2Y_2O_5$. On the basis of the present results and auxiliary thermodynamic data from the literature, phase relations in the Cu-Y-0 system at 723, 950, and 1373 K have been deduced.

Item Type: Journal Article http://dx.doi.org/10.1021/cm00005a010 Copyright of this article belongs to American Chemical Society. Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 13 Feb 2008 19 Sep 2010 04:42 http://eprints.iisc.ernet.in/id/eprint/12931

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