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Influence of thermally induced oxygen order on mobile ion dynamics in Gd_(2)(Ti_(0.65)Zr_(0.35))_(2)O_(7)

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Moreno, Karla J. and Fuentes, Antonio F. and Maczka, Miroslaw and Hanuza, Jerzy and Amador, Ulises and Santamaría Sánchez-Barriga, Jacobo and León Yebra, Carlos (2007) Influence of thermally induced oxygen order on mobile ion dynamics in Gd_(2)(Ti_(0.65)Zr_(0.35))_(2)O_(7). Physical review B, 75 (18). ISSN 1098-0121

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Official URL: http://dx.doi.org/10.1103/PhysRevB.75.184303


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http://journals.aps.org/Publisher


Abstract

We report on the influence of oxygen order in the oxygen-ion dynamics in the ionic conductor Gd_(2)(Ti_(0.65)Zr_(0.35))_(2)O_(7). The metastable Gd_(2)(Ti_(0.65)Zr_(0.35))_(2)O_(7) powders prepared by mechanical milling present an anion-deficient fluorite type of structure, stable up to about 800 °C. Thermal treatments at higher temperatures facilitate the gradual rearrangement of the cation and anion substructures and the relaxation of mechanochemically induced defects. Interestingly, metastable pyrochlores showing a very unusual cation distribution were observed during the thermally induced defect-recovery process. We have found that the ionic conductivity due to mobile oxygen ions increases significantly with increasing sintering temperature from 800 to 1500 °C as a result of a systematic decrease in the activation energy for the dc conductivity from 1.23 to 0.78 eV. Electrical conductivity relaxation is well described by stretched exponentials of the form φ(t)=exp[-(t/τ)^(1−n)], and the fractional exponent n decreases systematically from n=0.51 to 0.18 with increasing sintering temperature. These results are explained in terms of weaker ion-ion interactions in the increasingly ordered structure of the samples sintered at higher temperatures, and point to the importance of structural disorder in determining the dynamics of mobile oxygen ions.


Item Type:Article
Additional Information:

© 2007 The American Physical Society. This work was supported by Mexican Conacyt SEP- 2003-C02-44075 and Spanish MCYT MAT2004-3070.

Uncontrolled Keywords:Electrical relaxation; Constituent oxides; Solid-solutions; Pyrochlore; Microstructure; Condcutivity; Diffraction; Conductors; Diffusion.
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:30542
Deposited On:01 Jun 2015 09:50
Last Modified:10 Dec 2018 14:58

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