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High‐Temperature Phase Relations in the System Y 2 O 3 ‐Ta 2 O 5
Author(s) -
Yokogawa Yoshiyuki,
Yoshimura Masahiro
Publication year - 1991
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.1151-2916.1991.tb08262.x
Subject(s) - eutectic system , orthorhombic crystal system , phase diagram , phase (matter) , fluorite , crystallography , atmospheric temperature range , materials science , chemistry , crystal structure , thermodynamics , microstructure , physics , metallurgy , organic chemistry
The phase relations for the system y 2 o 3 –Ta 2 o 5 in the composition range 50 to 100 mol% Y 2 O 3 have been studied by solid‐state reactions at 1350°, 1500°, or 17000C and by thermal analyses up to the melting temperatures. Weberite‐type orthorhombic phases (W2 phase, space group C222 1 ), fluorite‐type cubic phases (F phase, space group Fm3m )and another orthorhombic phase (O phase, space group Cmmm )are found in the system. The W2 phase forms in 75 mol% Y 2 O 3 under 17000C and O phase in 70 mol% Y 2 O 3 up to 1700°C These phases seem to melt incongruently. The F phase forms in about 80 mol% Y 2 O 3 and melts congruently at 2454° 3°C. Two eutectic points seem to exist at about 2220°C 90 mol% Y 2 O 3 , and at about 1990°C, 62 mol% Y 2 O 3 . A Phase diagram including the above three phases were not identified with each other.