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Fractional Crystallization of Liquid Coexisting with α‐Ca 2 SiO 4 Solid Solution in the CaO–SiO 2 –Al 2 O 3 –Fe 2 O 3 Pseudoquaternary System
Author(s) -
Fukuda Koichiro,
Hattori Namiko,
Yoshida Hideto
Publication year - 2003
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.1151-2916.2003.tb03624.x
Subject(s) - crystallization , analytical chemistry (journal) , phase diagram , ferrite (magnet) , scanning electron microscope , liquid phase , chemical composition , microanalysis , atmospheric temperature range , mineralogy , chemistry , phase (matter) , crystallography , materials science , chromatography , thermodynamics , physics , organic chemistry , composite material
The phase stability in the pseudoquaternary CaO–SiO 2 –Al 2 O 3 –Fe 2 O 3 system has been studied over the temperature range of 1700° to 1360°C. The samples were prepared so that the mean chemical compositions were distributed between the end members of P 2 O 5 ‐bearing Ca 2 SiO 4 (C 2 S(ss)) and Ca 2 AlFeO 5 . They were examined by electron probe microanalysis, optical microscopy, and powder X‐ray diffractometry. Above 1378°C, α‐C 2 S(ss) and the liquid coexisted in equilibrium. Based on the temperature dependence of the chemical compositions of the two phases, the phase diagram was established in part of the pseudobinary Ca 2 SiO 4 –Ca 2 AlFeO 5 system. The Ca 2 AlFeO 5 contents of α‐C 2 S(ss) and liquid steadily increased from 3.4 to 5.2 and from 51.6 to 80.0 mass%, respectively, as the temperature decreased from 1700° to 1380°C. At temperatures between 1378° and 1368°C, the three‐phase mixture of α′ H ‐C 2 S(ss), ferrite, and liquid was stable. When α‐C 2 S(ss) and the liquid above 1378°C were cooled, both the remelting (metatectic) reaction of α‐C 2 S(ss) and the fractional crystallization of the liquid simultaneously occurred in the narrow temperature range of 1378° to 1368°C. In the latter reaction, the crystallized ferrite became enriched in Fe 2 O 3 with respect to Al 2 O 3 ; thus the relative composition of the differentiated liquid was reversed. During further cooling below 1368°C, the aluminate was crystallized out of the liquid. The resulting phase compositions (i.e., α′ H ‐C 2 S(ss), ferrite, and aluminate) were therefore distinct from those which were thermodynamically most stable (i.e., α′ H ‐C 2 S(ss) and ferrite).