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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. y Fuentes, Antonio F. y Maczka, Miroslaw y Hanuza, Jerzy y Amador, Ulises y Santamaría Sánchez-Barriga, Jacobo y 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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URL Oficial: http://dx.doi.org/10.1103/PhysRevB.75.184303

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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.

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

Palabras clave:Electrical relaxation; Constituent oxides; Solid-solutions; Pyrochlore; Microstructure; Condcutivity; Diffraction; Conductors; Diffusion.
Materias:Ciencias > Física > Electricidad
Ciencias > Física > Electrónica
Código ID:30542
Depositado:01 Jun 2015 09:50
Última Modificación:10 Dic 2018 14:58

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