Nanoscale Manipulation of Pyrochlore: New Nanocomposite Ionic Conductors

Abstract

The ionic conductivity of isometric pyrochlore, ideally A2B2O (7), is extremely sensitive to disordering of A- and B-site cations and oxygen anion vacancies. We report the first use of ion beam irradiation-induced disordering in Gd 2Ti 2O (7) to produce a strain-free, buried, disordered defect-fluorite layer approximately 12 nm thick within an ordered pyrochlore matrix. This approach provides a new means of creating nanoscale, mixed ionic-electronic conductors in pyrochlore ceramics, such as those required for solid-state electrochemical cells.

Lanthanum pyrochlores and the effect of yttrium addition in the systems La2−xYxZr2O7 and La2−xYxHf2O7

“…The magnitude of the node splitting, and hence the ring diameter, is on the order of 0.04-0.07 Å À1 normal to /111S* and appears to increase from La 0. 4 different to that of the other samples (Fig. 3e).…”

“…The pyrochlore structure type has great many uses, examples of which include magnetic materials [1,2], oxide fast ion conductors [3][4][5][6], and matrices for immobilisation of highly active radionuclides from nuclear wastes [7][8][9][10]. The last two applications are currently of major interest, as in both cases pyrochlores are capable of overcoming many technological problems, whilst remaining cost effective.…”

Ion beam irradiation of U-, Th- and Ce-doped pyrochlores

“…Isometric pyrochlores, A 2 B 2 O 7 , have been proposed as potential hosts for the immobilization of actinides, particularly Pu, due to their chemical durability and their ability to accommodate a wide variety of waste stream compositions [1][2][3][4][5][6][7]. The self-irradiation effects from the ␣-decay events of the incorporated actinides in the transplutonium-zirconate pyrochlores An 2 Zr 2 O 7 (An = Am, Cf) have recently been reported [8].…”

Movilidad de oxígeno en conductores iónicos A₂Ti_2-yZr_yO₇ (A: Y, Gd)

“…En este contexto, los óxidos de estructura pirocloro A 2 B 2 O 7 han demostrado ser de los candidatos más prometedores como conductores iónicos para su aplicación en pilas de combustible y sensores de oxígeno, y entre ellos, el sistema A 2 Ti 2-y Zr y O 7 con A=Y o Gd, resulta ser de particular interés (3,4). La conductividad iónica tiene lugar por el movimiento de vacantes de oxígeno, y el valor de la conductividad iónica de estos pirocloros resulta estar relacionado con el desorden de los cationes en los sitios A y B así como el desorden de las vacantes de oxígenos (3,5,6).…”