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Effect of temperature on formation of murataite and murataite-pyrochlore ceramics

Published online by Cambridge University Press:  11 February 2011

O. I. Kirjanova ,
S. V. Stefanovsky  and
S. V. Yudintsev
O. I. Kirjanova
Affiliation:
SIA Radon, 7th Rostovskii per. 2/14, Moscow 119121, RUSSIA
S. V. Stefanovsky
Affiliation:
SIA Radon, 7th Rostovskii per. 2/14, Moscow 119121, RUSSIA
S. V. Yudintsev
Affiliation:
IGEM RAS, Staromonetnii per. 35, Moscow 109017, RUSSIA
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Abstract

Processes of phases formation in the ceramic mixtures with basic compositions (wt.%) 10 CaO, 10 MnO, 5 Al2O3, 5 Fe2O3, 55 TiO2, 5 ZrO2, 10 UO2 (M1) and 8 CaO, 8 MnO, 4 Al2O3, 4 Fe2O3, 20 Gd2O3, 44 TiO2, 4 ZrO2, 8 UO2 (M4) were studied using X-ray diffraction, scanning and transmission electron microscopy. The batches were milled, compacted in pellets at 200 MPa, and heat-treated in a resistive furnace at 1100 °C, 1300 °C, 1400 °C, and 1500 °C as well as melted in a cold crucible at ∼1600 °C. Reactions in the mixtures heat-treated at 1100 °C were not completed and samples contained significant amount of unreacted and intermediate (altered rutile, cubic oxide solid solution, perovskite) phases. Within the temperature range 1100–1300 °C reactions are mainly completed and ceramics sintered at 1300 °C are composed of major murataite and minor rutile (M1) or major murataite and pyrochlore and minor zirconolite and perovskite (M4). However full homogenization at 1300 °C has not been reached yet and to obtain the ceramics with uniform compositions of the phases sintering at 1400 °C or melting at 1500–1600 °C were required.

In the ceramic sample M1 two murataite varieties with five- (murataite-5C) and eight-fold (mu-rataite-8C) fluorite-type unit cells were found. The sample M4 is composed of pyrochlore, murataite-8C and zirconolite-3O. In the sample M1 murataite-5C is enriched with U and Ca and depleted with iron group elements as compared to murataite-8C. Fraction of murataite-5C concentrates about 80% of total U and about 70% of Mn+Fe (corrosion products). Waste elements partitioning among the phases in the M4 sample depends significantly on temperature of heat-treatment.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II3.11
Copyright
Copyright © Materials Research Society 2003

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References

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