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Oxygen Grain‐Boundary Diffusion in Polycrystalline Mullite Ceramics
Author(s) -
Fielitz Peter,
Borchardt Günter,
Schmücker Martin,
Schneider Hartmut,
Willich Peter
Publication year - 2004
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.1151-2916.2004.tb07497.x
Subject(s) - mullite , grain boundary , materials science , ceramic , crystallite , impurity , oxygen , thermal diffusivity , analytical chemistry (journal) , grain boundary diffusion coefficient , mineralogy , diffusion , metallurgy , microstructure , chemistry , thermodynamics , physics , organic chemistry , chromatography
Oxygen tracer diffusivities of low‐ and high‐alumina mullite ceramics (72 wt% Al 2 O 3 , 28 wt% SiO 2 and 78 wt% Al 2 O 3 , 22 wt% SiO 2 , respectively) were determined. Gas/solid exchange experiments were conducted in an atmosphere enriched in the rare stable isotope 18 O, and the resulting 18 O isotope depth distributions were analyzed using SIMS depth profiling. The investigation showed that grain‐boundary diffusivities for both mullite ceramics were several orders of magnitude higher than mullite volume diffusivity. Activation enthalpies of oxygen diffusion were 363 ± 25 kJ/mol for the low‐alumina and 548 ± 46 kJ/mol for the high‐alumina materials. Because the glassy grain‐boundary films were not identified, the differences between the low‐ and high‐alumina materials might be explained by different impurity concentrations in the grain boundaries of the two materials.