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Characterization of a Cerium-Rich Pyrochlore-Based Ceramic Nuclear Waste Form

Published online by Cambridge University Press:  11 February 2011

R. Gieré ,
S. Segvich  and
E. C. BUCK
R. Gieré
Affiliation:
Earth&Atmospheric Sciences, Purdue University, West Lafayette, IN 47907–2051, USA; giere@purdue.edu
S. Segvich
Affiliation:
Earth&Atmospheric Sciences, Purdue University, West Lafayette, IN 47907–2051, USA; giere@purdue.edu Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
E. C. BUCK
Affiliation:
Pacific Northwest National Laboratory, P. O. Box 999, Richland, WA 99352, USA
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Abstract

Titanate ceramics have been proposed as candidate materials for immobilizing excess weapons plutonium. This study focuses on the characterization of a titanate-based ceramic through X-ray diffraction (XRD), electron probe microanalysis, and electron energy-loss spectroscopy (EELS). Three distinct phases have been identified, and their volume fraction was determined from element distribution maps using Scionimage-NIH Analysis software. This analysis revealed that the pyrochlore-group phase betafite (A2Ti2O7) forms the matrix of the ceramic and occupies 90.4% of the volume. Uniformly distributed in this matrix are perovskite (A2Ti2O6) and Hf-enriched rutile (TiO2), which account for 6.4 vol% and 3.1 vol%, respectively. The studied ceramic exhibits a very low porosity (0.3 vol%), which is characterized by small (<6 μm), rounded and isolated voids. In the studied ceramic, A-site cations are represented by Ca, rare earth elements, and Hf. The powder XRD pattern of the ceramic allowed refining the unit cell parameters for the cubic betafite, which is characterized by a cell edge of 10.132±0.003Å. The EELS data indicate that Ce is present as both Ce3+ and Ce4+ in betafite, whereas in perovskite, all Ce is trivalent.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II6.4
Copyright
Copyright © Materials Research Society 2003

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