Insight into the Effects of Fe Addition on the Local Structure and Electronic Properties of SrTiO3

This paper reports an experimental and theoretical investigation of the effects of adding Fe to the perovskite strontium titanate SrTiO 3 . The effects include changes in the short-order range structure as well as in the electronic and electrical properties. X-ray diffraction analysis reveals that the SrTi 1– x Fe x O 3 network shrinks with increasing Fe content, while X-ray absorption spectroscopy measurements of the Ti and Fe K-edge revealed the presence of some under-coordinated TiO 5 units created because of the partial replacement of Fe 3+ ions in the Ti 4+ site. UV–visible absorption spectra indicated a reduction in optical gap with increasing Fe content. The electronic structure and spin densities of STFO with x = 0, 0.0625, 0.125, 0.5, and 1 are calculated by the DFT method at the B3LYP computational level, showing a Jahn–Teller distortion of O atoms surrounding the Fe as well as the formation of under-coordinated TiO 5 units. From the electrical viewpoint, the results show that STFO is a mixed (ionic and electronic) conductor and that the electronic contribution becomes dominant with increasing Fe content.