Formation and stability regions of the high-temperature fluorite-related phase in the R{sub 2}O{sub 3}-Ta{sub 2}O{sub 5} system (R = La, Nd, Sm, Ho, Er, and Yb)
Journal Article
·
· Journal of the American Ceramic Society
OSTI ID:532932
- Tokyo Inst. of Tech., Midori, Yokohama (Japan). Research Lab. of Engineering Materials
Solid-state reaction and annealing of melts of samples in the R{sub 2}O{sub 3}-Ta{sub 2}O{sub 5} system (R is a rare-earth element, i.e., La, Nd, Sm, Ho, Er, and Yb) revealed a defect-fluorite phase (F-phase) at high temperatures. The formation region of this F-phase was in the region of {approximately}70--80 mol% R{sub 2}O{sub 3} for small rare-earth ions, such as erbium and ytterbium, but only in the region of {approximately}80 mol% R{sub 2}O{sub 3} at temperatures of >1,800 C for large rare-earth ions, such as the lanthanum-through-samarium series. This F-phase exhibited disordered cation and anion sublattices, such as (R{sub 0.8}Ta{sub 0.2})(O{sub 1.7}{open_square}{sub 0.3}). The F-phase decomposed to R{sub 2}O{sub 3} and an ordered phase--R{sub 3}TaO{sub 7} (orthorhombic weberite)--through a eutectic reaction at temperatures in the range of 1,500--1,700 C for gadolinium or larger rare-earth ions, whereas the F-phase was stable at 1,500 C for the small rare-earth ions (the erbium-through-ytterbium series).
- OSTI ID:
- 532932
- Journal Information:
- Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 8 Vol. 80; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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