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A Crystallographic Investigation of Calcium Diferrite
Author(s) -
CHESSIN HENRY,
TURKDOGAN E. T.
Publication year - 1962
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.1151-2916.1962.tb11068.x
Subject(s) - curie temperature , calcium , hexagonal crystal system , calcium oxide , crystallography , lattice constant , ferromagnetism , thermal expansion , materials science , oxide , chemistry , analytical chemistry (journal) , mineralogy , condensed matter physics , metallurgy , physics , diffraction , chromatography , optics
Calcium diferrite has been prepared at 1220°C in air. The lattice constants at 25° C of calcium diferrite have been determined by X‐ray powder data and have been based on the hexagonal system. They are a = 5.992 ± 0.004 A and co = 31.121 ± 0.008 A. The coefficients of thermal expansion were evaluated by X‐ray methods between‐130° and 25°C to be α 1 = 9.2 × 10 −6 per°C and 3 = 23 × lop 6 per °C, where a 3 is along the principal axis and α is perpendicular to it. The diferrite is ferromagnetic with a Curie point of 135°C. Comparison of the results obtained from the present work with those of some recent studies shows that the X‐ray data given by previous workers on compounds claimed to be Ca 3 FeleO 15 , Ca 4 Fe 17 O 29 , and Ca 4 Fe 4 O 25 are for calcium diferrite. The present work, however, also indicates that when mixtures of calcium diferrite plus ferrous oxide (up to 6 wt%) are heat‐treated at 1220°C, a new phase appears together with the diferrite.