X-ray Photoelectron Spectroscopy Study of Disordering inGd2(Ti1−xZr

Abstract

The dramatic increases in ionic conductivity in Gd2(Ti1-xZrx)2O7 solid solution are related to disordering on the cation and anion lattices. Disordering in Gd2(Ti1-xZrx)2O7 was characterized using x-ray photoelectron spectroscopy (XPS). As Zr substitutes for Ti in Gd2Ti2O7 to form Gd2(Ti1-xZrx)2O7 (0.25 < x < or =0.75), the corresponding O 1s XPS spectrum merges into a single symmetric peak. This confirms that the cation antisite disorder occurs simultaneously with anion disorder. Furthermore, the O 1s XPS spectrum of Gd2Zr2O7 experimentally suggests the formation of a split vacancy.

Influence of thermally induced oxygen order on mobile ion dynamics inGd2(Ti0.65Zr0.35)2Moreno1, Fuentes2, Mączka3 et al. 2007Phys. Rev. B445190View full textAdd to dashboardCite

“…The cation and anion substructures in the Gd 2 ͑Ti 1−y Zr y ͒ 2 O 7 solid solution disorder gradually as the Zr content increases, leading to the appearance of oxygen vacancies at 48f sites which are known to be responsible for oxygen hopping and diffusion. 5,9 Correspondingly, a marked increase in oxygen conductivity is observed in this system when y ജ 0.3, which has been related to the onset of the anion disordering. 9 Mechanical milling allows preparing partially disordered and metastable RE 2 Ti 2 O 7 pyrochlores, 10 obtained otherwise only by chemical substitution, ion irradiation, or pressureinduced compression.…”

“…4,5 Pyrochlore oxides A 2 B 2 O 7 are a very large family of compounds showing a great variety of physical and chemical properties as a function of chemical composition and the existing atomic ordering ͑disordering͒ and oxygen vacancies. Thus, while some pyrochlores such as Gd 2 Zr 2 O 7 are electronically insulating and fast high-temperature ionic conductors, others such as Gd 2 Mo 2 O 7 display at room temperature a metallic conducting behavior.…”

Estudio del régimen de pérdidas dieléctricas constantes en conductores iónicos con estructura de tipo pirocloro

“…En este trabajo se presentan datos de conductividad ac de varios circonatos conductores de iones oxígeno de fórmula general Gd 2 (Zr y Ti 1−y ) 2 O 7 , los cuales presentan una estructura de tipo pirocloro con un alto grado de desorden estructural y que han demostrado ser materiales prometedores para sustituir a fluoritas tales como la circonia estabilizada con itria como electrolito sólido en celdas de combustible cerámicas (21,22). Estructuralmente, los óxidos de este tipo se relacionan con la fluorita y como ésta, presentan conductividades considerables a elevadas temperaturas.…”

Crossover to nearly constant loss in ac conductivity of highly disordered pyrochlore-type ionic conductors

“…These materials present a highly disordered pyrochlore structure and have been shown to be promising candidates to substitute fluorites such as yttria-stabilized zirconia as the electrolyte currently used in fuel cells. 21,22 The cation and anion substructures in the Gd 2 ͑Zr y Ti 1−y ͒ 2 O 7 solid solution disorder gradually as the Zr content increases, leading to the appearance of oxygen vacancies at 48f sites which are known to be responsible for oxygen hopping and diffusion. 22,23 We show that the crossover to the NCL behavior can be clearly identified in these materials and it is found to be thermally activated with an activation energy E NCL much lower than the activation energy E dc for the dc conductivity.…”

“…21,22 The cation and anion substructures in the Gd 2 ͑Zr y Ti 1−y ͒ 2 O 7 solid solution disorder gradually as the Zr content increases, leading to the appearance of oxygen vacancies at 48f sites which are known to be responsible for oxygen hopping and diffusion. 22,23 We show that the crossover to the NCL behavior can be clearly identified in these materials and it is found to be thermally activated with an activation energy E NCL much lower than the activation energy E dc for the dc conductivity. We found that the values of E NCL do not change upon modifying composition unlike those of E dc , and, in fact, E NCL is similar to the energy barrier of the cages, E a , as calculated from computer simulations 24 and also estimated from electrical conductivity relaxation measurements at higher temperatures.…”