ISSN 0004-881X

Positron Annihilation Lifetime Spectroscopy of Off-Stoichiometric and Doped Gd₂Ti₂O₇

by E.R. Vance¹, J.H. Hadley, Jr.², F.H. Hsu²
1 Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia
2 Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA

Abstract

Positron annihilation lifetime spectroscopy (PALS) data confirm that the known tolerance of pyrochlore-structured Gd₂Ti₂O₇-based ceramics to Gd deficiency is due to Gd vacancies. An increase of ~25% of the majority spectrum lifetime ô1 in samples containing ~ 0.1 f.u. of Gd vacancies was observed, relative to that observed in pure Gd₂Ti₂O₇. In Gd₂Ti₂O₇ samples doped with Nb substituted on the Ti site to promote the formation of Gd or Ti vacancies, depending on the detailed phase design, up to ~ 0.4 f.u. of Gd and ~ 0.3 f.u. of Ti site vacancies could be accommodated.

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