Phase equilibria and elements partitioning in zirconolite-rich region of Ca-Zr-Ti-Al-Gd-Si-O system

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:572096

Knyazev, O A; Stefanovsky, S V ^[1]; Ioudintsev, S V; Nikonov, B S; Omelianenko, B I; Mokhov, A V; Yakushev, A I ^[2]

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1. SIA RADON, Moscow (Russian Federation)
2. Inst. of Geology of Ore Deposits, Moscow (Russian Federation)

Zirconolite-rich ceramics were produced by the cold crucible melting technique in an air atmosphere, at 1550 {+-} 50 C and 1 atm. Four samples with overall composition (in wt.%): 4.9-14.3 CaO; 19.0-41.3 ZrO{sub 2}; 24.1-42.6 TiO{sub 2}; 1.3-11.3 Al{sub 2}O{sub 3}; 6.8-30.0 Gd{sub 2}O{sub 3}; and 1.1-8.5 SiO{sub 2} have been studied. Total phases in the ceramics consist of major zirconolite and minor rutile, perovskite, zirconia, aluminium titanate, and glass. The Gd{sub 2}O{sub 3} content in zirconolite reaches up to 31.4 wt.% corresponding to the formula: (Ca{sub 0.4},Gd{sub 0.7})Zr{sub 1.0}(Ti{sub 1.4},Al{sub 0.5})O{sub 7.0}. The data on the phase composition agree well with coupled Gd incorporation into the mineral structure: Ca(II) + Ti(IV) = Gd(III) + Al(III), and 2Gd(III) = Ca(II) + Zr(IV). The highest Gd contents observed in the other phases are 25.4% for zirconia, 12.6% in glass, 8.8% in perovskite, and 1.4% for rutile. The rest of the elements` distribution in the samples are analyzed.

• OSTI ID: 572096
• Report Number(s): CONF-961202--
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
CORROSION RESISTANCE
FABRICATION
HIGH-LEVEL RADIOACTIVE WASTES
PHASE STUDIES
WASTE FORMS
ZIRCONOLITE