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Radiation Damage in Pyrochlore and Related Compounds

Published online by Cambridge University Press:  21 March 2011

G.R. Lumpkin
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK ANSTO Materials, Private Mail Bag 1, Menai 2234, NSW, Australia
K.R. Whittle
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
S. Rios
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
K. Trachenko
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
M. Pruneda
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
E.J. Harvey
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
S.A.T. Redfern
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
K.L. Smith
Affiliation:
ANSTO Materials, Private Mail Bag 1, Menai 2234, NSW, Australia
N.J. Zaluzec
Affiliation:
Materials Science Division, Argonne National Laboratory, Argonne, IL, USA
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Abstract

The radiation damage properties of synthetic pyrochlore-defect fluorite compounds containing lanthanides on the A-site and Ti, Zr, Sn, and Hf on the B-site have been studied extensively using Kr ion irradiation. Using statistical analysis, we show that the results can be quantified in terms of the critical temperature for amorphization, structural parameters, classical Pauling electronegativity difference, and defect energies. The best current model is able to predict the critical temperature to within about 80 degrees Kelvin. The model indicates that radiation tolerance is correlated with an increase in the X anion coordinate toward the value characteristic of the defect fluorite topology, a smaller unit cell dimension, and lower defect energies. Our analysis also demonstrates that radiation tolerance is promoted by an increase in the Pauling cation-anion electronegativity difference or, in other words, an increase in the ionicity of the chemical bonds. Of the two possible cation sites in ideal pyrochlore, the B-site cation appears to play the major role in bonding. This result is supported, for a subset of pyrochlore compounds, by ab initio calculations, which reveal a correlation between the Mulliken overlap populations of the B-site cation and the critical temperature.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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