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The Series MgCr 2 O 4 ‐MgFe 2 O 4
Author(s) -
ALLEN WALTER C.
Publication year - 1968
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.1151-2916.1968.tb15673.x
Subject(s) - spinel , series (stratigraphy) , solid solution , thermodynamics , refractive index , standard deviation , chemistry , materials science , mathematics , metallurgy , statistics , physics , paleontology , optoelectronics , biology
The characteristics of spinels in the series MgCr 2 O 4 ‐MgFe 2 O 4 were determined. The plot of cell size vs. molar composition is unusual in series showing complete solid solution because an unusually large deviation from Vegard's law was observed. This deviation is caused by changes in spinel structure with composition and temperature, and an equation was derived which applies a correction in terms of the degree of inversion. The effects of temperature on compositions high in MgFe 2 O 4 include changes in density and refractive index. Solid solution of forsterite in MgCr 2 O 4 decreases the cell size to 8.329 A but apparently is less than 1%. Changes in composition caused by vapor loss or by dissociation are small enough that this series is essentially binary below 1400° C.