Thermogravimetric analysis and a coulometric titration technique were used
to measure the relative changes in oxygen stoichiometry of Sr-0.97(Ti,Fe)O3
-delta materials with temperature and oxygen partial pressure, and these re
sults were used to re-examine the defect chemistry. These materials undergo
significant weight gain on cooling which was attributed to changes in vale
nce of Fe ions. The oxygen gain attained on cooling from 1300 degreesC to r
oom temperature indicates that Fe3+ and Fe4+ coexist in these materials, an
d that the concentration of oxygen vacancies remains relatively high in wid
e ranges of working conditions but may vary with temperature, and/or oxygen
partial pressure. (C) 2000 Elsevier Science B.V. All rights reserved.