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Distribution of Oxide in a Bed of Thermally Decomposed ZrF 4 · H 2 O and Its Effect on ZrF 4 Sublimation
Author(s) -
Ewing Kenneth J.,
Wright Barbara M.,
Jaganathan James,
Aggarwal Ishwar D.
Publication year - 1992
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.1151-2916.1992.tb07217.x
Subject(s) - sublimation (psychology) , oxide , fluoride , zirconium , thermogravimetric analysis , materials science , analytical chemistry (journal) , mineralogy , chemistry , metallurgy , inorganic chemistry , psychology , organic chemistry , psychotherapist , chromatography
The oxide distribution in a bed of thermally decomposed zirconium fluoride monohydrate (ZrF 4 · H 2 O) is determined via inert gas carbon fusion analysis (LECO). It is shown that the oxide concentration in the bed of thermally decomposed ZrF 4 · H 2 O is a function of position in the crucible. The oxide concentration in the crucible decreases in the order, from greatest to least, surface ≫ bottom > sides > middle. XRD analysis and thermogravimetric analysis indicate that the predominant phase in the bottom, side, and middle regions of the bed is ZrF 4 , while in the surface region Zr 7 O 9 F 10 is the predominant phase with traces of ZrO 2 and ZrF 4 present. It is proposed that the production of HF (g) from the thermal decomposition of the bottom and side regions of the bed of ZrF 4 · H 2 O causes the central region of the bed to contain a higher concentration of HF (g) than any other region in the bed. The higher concentration of HF (g) in the central region of the bed of decomposing ZrF 4 · H 2 O is expected to shift the equilibrium from formation of zirconium oxyfluoride and elimination of HF (g) toward the formation of ZrF 4 and elimination of water. Thermal decomposition of different masses of ZrF 4 · H 2 O demonstrates that the oxide constration increases in the middle of the bed as the initial mass decreases. This result is consistent with the proposed mechanism for production of different phases in the bed of material. It is also shown that thermally decomposed ZrF 4 · H 2 O can be used as feedstock for preparation of low‐oxide zirconium fluoride via sublimation. The best results for sublimation from this feedstock material are obtained when the surface, which contains the highest oxide concentration, is removed before sublimation.