Dielectric relaxation in YTTRIA-doped Ceria solid solutions |
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Authors: | Da Yu Wang AS Nowick |
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Institution: | Henry Krumb School of Mines, Columbia University, NY 10027, U.S.A. |
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Abstract: | The nature of the defects present in Y2O3-doped CeO2 is explored by means of dielectric relaxation, employing primarily the thermally-stimulated depolarization current (TSDC) technique. For Y2O3 concentrations ? 1 mole %, two relaxation peaks are observed. The lower-temperature peak shows a dielectric relaxation rate, τ?1 which is the relaxation rate of the corresponding anelastic relaxation. This proves that the peak is due to nn, 〈111〉 oriented, (YVO) pairs, where VO represents the oxygen vacancy. These pairs are positively charged defects which are compensated by an equal number of isolated Ý. The upper peak is a broad peak whose position varies with Y2O3 concentration in the same manner as the activation enthalpy for the ionic conductivity. The peak is not due to simple dipoles, but to relaxation of the array of alternately charged (YVO) and Ý defects by the redistribution of oxygen-ion vacancies. A simple model, in which these defects form a superlattice containing wrong pairs, explains the essential features of the upper peak. |
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