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Chemical Instability of Metal‐Deficient Hexagonal Ferrites with W Structure
Author(s) -
LOTGERING F. K.,
VROMANS P. H. G. M.
Publication year - 1977
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.1151-2916.1977.tb15524.x
Subject(s) - barium , metal , hexagonal crystal system , annealing (glass) , materials science , oxygen , atmospheric temperature range , ion , decomposition , crystallography , instability , analytical chemistry (journal) , chemistry , metallurgy , physics , thermodynamics , mechanics , organic chemistry , chromatography
The hexagonal ferrite W=BaFe 2+ 2 Fe 3+ 16 O 27 , which is in equilibrium with oxygen under 0.015 atm at 1350 ° C, is oxidized in the range 250 ° to 1100 ° C in the same atmosphere to BaFe 3+ 16+2x Fe 2 2‐3x > x O 27 with 2–3 x <0.03. The metal‐deficient W structure is chemically unstable and decomposes after longer annealing at the same temperature. This difference in oxidation and decomposition rate is attributed to a difference in the diffusion rate of barium and iron ions.