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Energetics of rare-earth-doped hafnia

Published online by Cambridge University Press:  03 March 2011

Petra Simoncic  and
Alexandra Navrotsky
Petra Simoncic
Affiliation:
Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU) and Thermochemistry Facility, University of California at Davis, Davis, California 95616
Alexandra Navrotsky*
Affiliation:
Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU) and Thermochemistry Facility, University of California at Davis, Davis, California 95616
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

The enthalpies of formation of rare-earth (RE)-doped Hf1−xRExO2−x/2 solid solutions (RE = Sm, Gd, Dy, Yb; x = 0.25 to 0.62) with respect to the oxide end members, monoclinic HfO2 and C-type REO1.5, were determined using oxide melt solution calorimetry. The enthalpies of formation fit a function quadratic in composition. The strongly negative interaction parameters in all solid solutions confirm a strong tendency for short-range order. Though strongly negative for all systems, the interaction parameters become less negative with increasing ionic potential (decreasing RE radius). Crystallization energetics were investigated for amorphous coprecipitation products with x = 0.4. The energy difference between the crystalline (fluorite and pyrochlore) and amorphous phases decreases with decreasing dopant radius. This suggests that systems doped with small RE ions have more similar local structures in the fluorite and amorphous phases. These observations may result in a smaller kinetic barrier to recrystallization and account for the greater radiation resistance of materials with smaller RE cations.

Keywords

CalorimetryIonic conductorLanthanide
Type
Articles
Information
Journal of Materials Research , Volume 22 , Issue 4 , April 2007 , pp. 876 - 885
Copyright
Copyright © Materials Research Society 2007

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