Jahn-Teller distortion around Fe4+ in Sr (Fex Ti1-x) O3-δ from x-ray absorption spectroscopy, x-ray diffraction, and vibrational spectroscopy

Sr (Fex Ti1-x) O3-δ perovskites (strontium titanate ferrite solid solution) with well-defined oxygen stoichiometry have been studied as a function of iron concentration by x-ray diffraction, Fe and Ti K -edge x-ray absorption spectroscopy (XAS), and vibrational (Raman and infrared) spectroscopy. In reduced Sr (Fex Ti1-x) O3-x2 samples, the analysis of the Fe K -edge extended x-ray absorption fine structure indicates the expected presence of oxygen vacancies VO in the first coordination shell of Fe3+ ions. In oxidized Sr (Fex Ti1-x) O3 samples, the combination of XAS and vibrational spectroscopy results yields strong indications for the presence of a Jahn-Teller distortion around Fe4+ ions, which is most pronounced for x 0.03 and decreases for higher iron concentrations.