High-Temperature Phase Relations in the Sc2O3-Ta2O5 System |
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Authors: | Yoshiyuki Yokogawa Masahiro Yoshimura |
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Affiliation: | National Industrial Research Institute of Nagoya, Nagoya 462–8510, Japan;Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226–8503, Japan |
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Abstract: | The phase relations for the Sc2O3-Ta2O5 system in the composition range of 50-100 mol% Sc2O3 have been studied by using solid-state reactions at 1350°, 1500°, or 1700°C and by using thermal analyses up to the melting temperatures. The Sc5.5Ta1.5O12 phase, defect-fluorite-type cubic phase (F-phase, space group Fm 3 m ), ScTaO4, and Sc2O3 were found in the system. The Sc5.5Ta1.5O12 phase formed in 78 mol% Sc2O3 at <1700°C and seemed to melt incongruently. The F-phase formed in ~75 mol% Sc2O3 and decomposed to Sc5.5Ta1.5O12 and ScTaO4 at <1700°C. The F-phase melted congruently at 2344°± 2°C in 80 mol% Sc2O3. The eutectic point seemed to exist at ~2300°C in 90 mol% Sc2O3. A phase diagram that includes the four above-described phases has been proposed, instead of the previous diagram in which those phases were not identified. |
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