Oxygen nonstoichiometry of Ce1-ySmyO2-0.5y-x (y = 0.1, 0.2)

Citation
T. Kobayashi et al., Oxygen nonstoichiometry of Ce1-ySmyO2-0.5y-x (y = 0.1, 0.2), SOL ST ION, 126(3-4), 1999, pp. 349-357
Citations number
17
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
SOLID STATE IONICS
ISSN journal
01672738 → ACNP
Volume
126
Issue
3-4
Year of publication
1999
Pages
349 - 357
Database
ISI
SICI code
0167-2738(199911)126:3-4<349:ONOC(=>2.0.ZU;2-5
Abstract
Dependence of oxygen nonstoichiometry of Ce1-ySmyO2-5,5-x (y = 0.1, 0.2) on temperature, T, and oxygen partial pressure, P-O2, was investigated by the rmogravimetry. Based on the experimental data, partial molar enthalpy, Delt a (H) over bar(O), and entropy, Delta (S) over bar(O), of oxygen were calcu lated and the defect model was discussed. In the region where oxygen defici ency, x, was below 0.02 of Ce0.9Sm0.1O1.95-x, Delta (H) over bar o was inde pendent of x, indicating that an ideal solution model was applicable for th e distribution of oxygen vacancies. Linear relationship between Delta (H) o ver bar(O) and x observed in the region 0.02 less than or equal to x less t han or equal to 0.05 of Ce0.9Sm0.1O1.95-x indicated that the regular soluti on model was applicable in this range. Experimentally obtained Delta (S) ov er bar(O), of Ce0.9Sm0.1O1.95-x with x less than or equal to 0.05 also agre ed with a theoretical calculated ones based on an ideal solution or a regul ar solution model, in which random distribution of oxygen vacancies was ass umed. From the analysis of dependence of Delta (H) over bar(O) and Delta (S ) over bar(O) on x, it was revealed that an ideal solution model for the di stribution of oxygen vacancies was applicable in Ce0.8Sm0.2O1.9-x with x ra nge below 0.05. With the increase of x larger than 0.05, deviation from ide al or regular solution model was observed for the both specimens, which cou ld be attributed to the association among oxygen vacancies. The oxygen nons toichiometry, Delta (H) over bar(O) and Delta (S) over bar(O) of Sm-doped C eO2 were compared with those of Gd-doped CeO2. (C) 1999 Elsevier Science B. V. All rights reserved.