Dilute iron‐doped polycrystalline strontium titanate: Tracking iron valence and local interactions

Abstract

AbstractThe mixed‐valence states of dilute Fe (0.2, 0.5, and 1.2 mol%) in bulk polycrystalline (SrTiO3) (STO) were determined. Specimens were sintered in air or O2 at 1500°C or 1300°C with the intent to quantify the relative valence states of Fe in the context of understanding microstructure development of Fe‐doped STO. Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, and magnetometry were combined to track changes in Fe valence, and Raman spectroscopy and X‐ray diffraction were used to describe the associated structural changes. Small concentrations of defect associates were detected, but the majority of Fe′Ti acceptors are isolated from oxygen vacancies. As doping increases, negative exchange interactions increase, consistent with an increase in the concentration of configurations. Additionally, the fraction of dopants existing as isovalent increased with of the sintering atmosphere and with total Fe content.