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High‐Temperature Phase Relations in the Sc 2 O 3 ‐Ta 2 O 5 System
Author(s) -
Yokogawa Yoshiyuki,
Yoshimura Masahiro
Publication year - 1999
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1999.tb01962.x
Subject(s) - eutectic system , phase diagram , phase (matter) , melting point , atmospheric temperature range , fluorite , materials science , analytical chemistry (journal) , crystallography , chemistry , microstructure , thermodynamics , metallurgy , physics , organic chemistry , composite material , chromatography
The phase relations for the Sc 2 O 3 ‐Ta 2 O 5 system in the composition range of 50‐100 mol% Sc 2 O 3 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 Sc 5.5 Ta 1.5 O 12 phase, defect‐fluorite‐type cubic phase (F‐phase, space group Fm 3 m ), ScTaO 4 , and Sc 2 O 3 were found in the system. The Sc 5.5 Ta 1.5 O 12 phase formed in 78 mol% Sc 2 O 3 at <1700°C and seemed to melt incongruently. The F‐phase formed in ∼75 mol% Sc 2 O 3 and decomposed to Sc 5.5 Ta 1.5 O 12 and ScTaO 4 at <1700°C. The F‐phase melted congruently at 2344°± 2°C in 80 mol% Sc 2 O 3 . The eutectic point seemed to exist at ∼2300°C in 90 mol% Sc 2 O 3 . 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.