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Composition Microheterogeneity of Uvarovite–Grossularite Garnets
Author(s) -
Carda Juan,
Monrós Guillermo,
Tena Ma. Angeles,
Escribano Purificación,
Rincón Jesús Ma.
Publication year - 1994
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.1151-2916.1994.tb07103.x
Subject(s) - scanning electron microscope , transmission electron microscopy , analytical chemistry (journal) , microstructure , mineralogy , solid solution , materials science , gehlenite , cristobalite , microanalysis , crystallography , phase (matter) , chemistry , quartz , metallurgy , nanotechnology , chromatography , composite material , organic chemistry
A solid‐solution series with up to 50 mol% uvarovite (Ca 3 Cr 2 Si 3 O 12 ) and grossularite (Ca 3 Al 2 Si 3 O 12 ) was synthesized by the sol–gel method at 1543 K. Colloidal silica was used as the starting reagent, together with chloride salts of the remaining components. X‐ray diffraction analysis of the evolution of the systems showed the formation of uvarovite in a nominal composition of 100 mol% uvarovite; a garnet‐phase solid solution; and gehlenite (Ca 2 Al 2 SiO 7 ), pseudowollastonite (α‐CaSiO 3 ), and α‐cristobalite in a nominal composition of 100 mol% grossularite. In some samples, small amounts of impurity phases appeared along with the major phase. The general microstructure was observed by scanning electron and transmission electron microscopy, and an agglomeration of crystals with 2‐μm average size was revealed. The crystals were similar and rounded in shape for all compositions. Additional observations carried out by transmission electron microscopy (TEM) (using the powder replica method) showed that the end series consists of cubic crystals displaying some deformation. Quantitative and semiquantitative scanning electron microscopy/energy‐dispersive X‐ray (SEM/EDX) and transmission electron microscopy/scanning electron microscopy/energy‐dispersive X‐ray (TEM/STEM/EDX) microanalysis (by the Cliff‐Lorimer method, working at 200 kV) were also conducted in all compositional ranges of the solid solutions synthesized in the present study.