Phase relations in the system Cu-Gd-O and Gibbs energy of formation of CuGd[sub 2]O[sub 4]

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02646604· OSTI ID:6301496

Jacob, K T; Mathews, T; Hajra, J P ^[1]

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1. Indian Inst. of Science, Bangalore (India). Dept. of Metallurgy

The phase relations in the system Cu-Gd-O have been determined at 1,273 K by X-ray diffraction, optical microscopy, and electron microprobe analysis of samples equilibrated in quartz ampules and in pure oxygen. Only one ternary compound, CuGd[sub 2]O[sub 4], was found to be stable. The Gibbs free energy of formation of this compound has been measured using the solid-state cell Pt, Cu[sub 2]O + CuGd[sub 2]O[sub 4] + Gd[sub 2]O[sub 3]//(Y[sub 2]O[sub 3])ZrO[sub 2]//CuO + Cu[sub 2]O, Pt in the temperature range of 900 to 1,350 K. For the formation of CuGd[sub 2]O[sub 4] from its binary component oxides, CuO (s) + Gd[sub 2]O[sub 3] (s) [r arrow] CuGd[sub 2]O[sub 4] (s) [Delta]G[degree] = 8230 - 11.2T([plus minus]50)J/mol. Since the formation is endothermic, CuGd[sub 2]O[sub 4] becomes thermodynamically unstable with respect to CuO and Gd[sub 2]O[sub 3] below 735 K. When the oxygen partial pressure over CuGd[sub 2]O[sub 4] is lowered, it decomposes according to the reaction 4CuGd[sub 2]O[sub 4] (s) [r arrow] 4Gd[sub 2]O[sub 3] (s) + 2Cu[sub 2]O (s) + O[sub 2] (g) for which the equilibrium oxygen potential is given by [Delta][mu][sub o][sub 2] = [minus]227,970 + 143.2T([plus minus]500)J/mol. An oxygen potential diagram for the system Cu-Gd-O at 1,273 is presented.

• OSTI ID: 6301496
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24:7; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER OXIDES
FORMATION FREE ENERGY
PHASE STUDIES
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DECOMPOSITION
ELECTRON MICROPROBE ANALYSIS
EXPERIMENTAL DATA
OPTICAL MICROSCOPY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
X-RAY DIFFRACTION
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COHERENT SCATTERING
COPPER COMPOUNDS
DATA
DIFFRACTION
ENERGY
FREE ENERGY
GADOLINIUM COMPOUNDS
INFORMATION
MICROANALYSIS
MICROSCOPY
NONDESTRUCTIVE ANALYSIS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SCATTERING
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