Phase equilibria of the MgO-Cu{sub 2}O-CuO system

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Materials Research Bulletin

DOI:https://doi.org/10.1016/S0025-5408(96)00184-5· OSTI ID:455237

Paranthaman, M; David, K A; Lindemer, T B ^[1]

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1. Oak Ridge National Lab., TN (United States)

Phase equilibria of the MgO-Cu{sub 2}O-CuO system have been determined in air at temperatures ranging from 850 to 1,100 C. The starting compositions ranged from 0 to 100% Mg in (Mg{sub 1{minus}x}Cu{sub x})O. CuO was quite soluble in MgO. The solubility of CuO in MgO at 850 C was about 9% and at 1,050 C was about 20%. The only known ternary Guggenite phase had a composition of Cu{sub 2}MgO{sub 3}. The Guggenite phase exists in three forms, namely, Guggenite A (G{sub A}, orthorhombic, space group Pmmn(59)), Guggenite B (G{sub B}, orthorhombic, space group I(0)), and Guggenite X (G{sub X}, monoclinic). Guggenite A was obtained as a single phase in air at x{sub CuO} = 67% (i.e., 67% CuO and 33% MgO) and 1,000 C. It undergoes a phase transition to the Guggenite X phase when it is heated above 1,050 C. The Guggenite B phase was obtained in a mixture at x{sub CuO} = 75% and at temperatures above 1,050 C. MgO was not found to be soluble in CuO. For samples with x{sub CuO} {ge} 67%, the Guggenite A phase coexisted with tenorite (CuO, monoclinic) at temperatures {le} 1,000 C and above 1,021 C, it was in equilibrium with cuprite (Cu{sub 2}O, cubic). For CuO compositions between 20% and 67%, a mixture of Guggenite A phase and the periclase phase (MgO, cubic) was obtained at temperatures {le} 1,000 C. The decomposition of Cu{sub 2}MgO{sub 3} (Guggenite A) phase was determined at several oxygen partial pressures and the Gibbs free energy of formation of this phase was also calculated.

• DOE Contract Number: AC05-96OR22464
• OSTI ID: 455237
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 2 Vol. 32; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER OXIDES
EQUILIBRIUM
EXPERIMENTAL DATA
FORMATION FREE ENTHALPY
MAGNESIUM OXIDES
PARTIAL PRESSURE
PHASE DIAGRAMS
PHASE STUDIES
PHASE TRANSFORMATIONS
SOLUBILITY
TEMPERATURE RANGE 1000-4000 K