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Oxidation Equilibrium of Iron in Borosilicate Glass
Author(s) -
GOLDMAN DON S.
Publication year - 1983
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.1151-2916.1983.tb10018.x
Subject(s) - borosilicate glass , ferrous , ferric , oxygen , chemistry , silicate , inorganic chemistry , mineralogy , alkali metal , analytical chemistry (journal) , redox , atmospheric temperature range , ion , thermodynamics , physics , chromatography , organic chemistry
Ferrous/ferric equilibria were determined in alkali‐alkaline‐earth borosilicate glass as a function of temperature, oxygen partial pressure, and glass composition. Expected linear relations are found between log(Fe 2+ /Fe 3+ ) and log( p O 2 ) or 1/ T . The slopes of the correlation with 10g( p O 2 ) are near the expected value of ‐0.25, but are found to decrease with increasing temperature. Reaction enthalpies determined from the correlation with 1/ T of –100 to –116 kJ/mol are similar to those reported for other silicate glasses. The ferroudferric equilibrium is not dependent on total iron content in the range 0.5 to 0.09% Fe 2 O 3 . More reducing conditions are required at lower temperatures to stabilize the amber chromophore. The ferroudferric equilibria are correlated to the number of bridging and nonbridging oxygen ions in the glass. The results suggest that the oxidation‐reduction reaction can be written as: Fe 2+ + ( 1 / 4 )O 2 + ( 3 / 2 )O 2‐ = FeO 2 −