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Phase composition of the ceramics based on Rare Earth, Manganese and Titanium Oxides

Published online by Cambridge University Press:  21 March 2011

S.V. Stefanovsky ,
S.V. Yudintsev ,
B.S. Nikonov  and
O.I. Stefanovsky
S.V. Stefanovsky
Affiliation:
SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121, RUSSIA
S.V. Yudintsev
Affiliation:
Institute of Geology of Ore Deposits, Staromonetnii lane 35, Moscow 109017, RUSSIA
B.S. Nikonov
Affiliation:
Institute of Geology of Ore Deposits, Staromonetnii lane 35, Moscow 109017, RUSSIA
O.I. Stefanovsky
Affiliation:
SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121, RUSSIA
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Abstract

Ceramics in systems with rare earth (REE = Y, Sm, Gd), manganese, and titanium oxides are considered as potential matrices for immobilization of REE- and actinide-containing radioactive wastes. Ceramics of this type were synthesized from oxide mixtures by a cold pressing and sintering method at temperatures of 1300-1400 °C as well as plasma heating. Major phases in the ceramics were found to be the phases of the pyrochlore-murataite polysomatic series with three- (3C), five- (5C), and seven-fold (7C) elementary fluorite unit cell. Perovskite/pyrophanite, hibonite/loveringite as well as garnet in the samples contained extra Fe and Al oxides were present as minor phases. Formation of the murataite, to be exact – structures built from murataite and pyrochlore modules, is more characteristic of the Y-bearing systems rather than the systems with heavier lanthanides. Increase of ionic radius of the REE trends towards formation of the pyrochlore structure phases whereas occurrence of large-size cations (La) stimulates formation of the perovskite structure phase. In the Y-bearing system murataite formation takes place at relative low Y2O3 concentrations (<15 mole %) and TiO2 content as high as ∼60 mole % and MnOx – 15-20 mole %. Higher Y2O3 concentrations and Gd2O3 substitution for Y2O3 yields preferably the pyrochlore phase or may favor formation of the phase with the 7C polytype.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 932: Symposium – Scientific Basis for Nuclear Waste Management XXIX , 2006 , 63.1
Copyright
Copyright © Materials Research Society 2006

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References

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