Thermodynamic behavior of various phases appearing in the CeZrO{sub 4}-CeZrO{sub 3.5} system and the formation of metastable solid solutions
- Osaka Univ., Suita, Osaka (Japan). Dept. of Materials Science and Processing
In order to investigate the thermodynamic behavior of t{prime}, t{sup *}, and {kappa} phases with the composition, CeZrO{sub 4}, the equilibrium oxygen partial pressure, p{sub O{sub 2}}, over their mixtures with pyrochlore (Ce{sub 2}Zr{sub 2}O{sub 7+x}) was measured utilizing an electrochemical cell: Pt, {l_brace}CeZrO{sub 4}(t{prime}, t{sup *}, or {kappa} phase) + Ce{sub 2}Zr{sub 2}O{sub 7+x}{r_brace}/ZrO{sub 2}(+Y{sub 2}O{sub 3})/air, Pt. The conclusions described below were derived: the thermodynamic stability of the {kappa} phase is the lowest in the CeO{sub 2}0ZrO{sub 2} system. The {kappa} phase forms metastable solid solutions with the pyrochlore phase; it was virtually stable around 1,123 K. Two kinds of tetragonal phases exist, tet. (high temp.) and tet. (low temp.), which may correspond to t{prime} and t{sup *}, respectively. A change in p{sub o{sub 2}} corresponding to the phase transitions: {kappa} {yields} t{prime} and t{prime} {r_reversible} t{sup *} was observed. The standard Gibbs energies of formation, {Delta}G{degree}, of {kappa}(CeZrO{sub 4}) and t{sup *}(CeZeO{sub 4}) for the reaction: 1/2Ce{sub 2}Zr{sub 2}O{sub 7} + 1/4 O{sub 2} {yields} CeZrO{sub 4} were evaluated from the emf data.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 624311
- Journal Information:
- Journal of the Electrochemical Society, Vol. 145, Issue 4; Other Information: PBD: Apr 1998
- Country of Publication:
- United States
- Language:
- English
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