Temperature-dependent 57Fe Mössbauer spectroscopy and local structure of mullite-type Bi2(FexAl1–x)4O9 (0.1≤x≤1) solid solutions

Oxides of the chemical composition Bi (Fe Al (0.1≤ ≤1) possessing a mullite-type structure have been investigated using Fe Mössbauer spectroscopy in the temperature range between room temperature and 1073K. The spectra have been fitted with two quadrupole doublets for Fe ions in octahedral and tetrahedral oxygen coordination. The distribution of iron on the two inequivalent structural sites has been determined from the relative areas of the subspectra. The site occupancy is found to be random within experimental error: it does not exhibit any preference of iron for the octahedral or tetrahedral sites, either as a function of temperature or with a dependence on the composition of the solid solutions.