Phase equilibria and thermodynamics of coexisting phases in rare-earth element--iron--oxygen systems. I. The cerium--iron--oxygen system

Journal Article · Thu Jul 01 04:00:00 EDT 1976 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(76)90103-1· OSTI ID:7346623

Tretyakov, Yu D; Sorokin, V V; Kaul, A R; Erastova, A P

It is shown that in the Ce--Fe--O system only one ternary compound with a perovskite structure, the orthoferrite CeFeO/sub 3/, is formed. The crystallographic properties of cerium ferroperovskite are defined more accurately. The thermodynamics of its oxidation and reduction over a temperature range of 900 to 1200/sup 0/C are studied using the emf method with a solid electrolyte. It is shown that the free energy of cerium orthoferrite formation from the oxides according to the reaction 1/2Ce/sub 2/O/sub 3/ + 1/2Fe/sub 2/O/sub 3/ = CeFeO/sub 3/, derived from data on the equilibrium oxidation of CeFeO/sub 3/, differs very little from the value of ..delta..G/sup 0/, calculated from the magnitude of the equilibrium pressure of oxygen over the orthoferrite and reduction products coexisting with it. Phase equilibria and the thermodynamics of coexisting phases in the Ce--Fe--O system were investigated. Equilibrium diagrams are constructed which define the character of the changes taking place in the Ce--Fe--O system during changes in partial oxygen pressure, temperature, and composition of the initial oxide mixture. Thus, we have equilibrium diagrams of the type Po/sub 2/ = f(composition) with T = constant; Po/sub 2/ = f(1/T) with one composition parameter fixed; and T = f(composition) with Po/sub 2/ = constant.

• Research Organization: Moscow State Univ.
• OSTI ID: 7346623
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 18:3; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
FERRIMAGNETIC MATERIALS
FERRITES
IRON COMPOUNDS
IRON OXIDES
MAGNETIC MATERIALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
RARE EARTH COMPOUNDS
THERMODYNAMICS
TRANSITION ELEMENT COMPOUNDS
VERY HIGH TEMPERATURE