Defect structure of the mixed ionic–electronic conducting Sr[Ti,Fe]Ox solid-solution system — Change in iron oxidation states and defect complexation

Characterization of non-stoichiometric co-sputtered Ba0.6Sr0.4(Ti1 − x Fe x )1 + x O3 − δ thin films for tunable passive microwave applications

“…3 is dominated by a strong resonance at 335.7 mT with a g-value of 2.002. This g-value correlates well with trivalent Fe 3+ that is octahedrally coordinated by six oxygen ions [37]. Accordingly, the iron is incorporated on the B-site of the ABO 3 perovskite structure where charge compensating oxygen vacancies are in remote coordination spheres.…”

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

“…We recall 30,73 that undoped STO is naturally a semiconductor, but with a wide band gap that exceeds 3 eV; therefore, it is characterized by low conductivities. Replacing Ti 4+ by Fe 3+ ions normally produces, on the one hand, a decrease in band gap to around 2 eV and, on the other hand, an increase in defect concentration, such as multivalent Fe centers, electron holes, and oxygen vacancies (V ö) , 74 and the material turns out to be a mixed electronic (σ e ) and ionic (σ i ) conductor. To understand the results depicted in Figure 7a, it is worth remembering for reference that conductivity satisfies an expression of the type σ = Nqμ, where N represents the concentration of charge carriers, q the charge value attributed to these carriers, and μ their mobility throughout the dielectric medium.…”

Effects of thermal processing and iron doping in co-sputtered barium strontium titanate thin films

“…The broad resonance at *340 mT represents octahedral coordinated Fe 3? cations incorporated at the B-site of the perovskite structure [17,21,39]. The corresponding signal intensity is invariant upon temperature.…”

“…can only be detected by XPS and not for the experimental conditions relevant for the X-band, the incorporation of iron as divalent Fe 2? cannot be directly monitored by EPR [21].…”

“…The defect complexes, which act upon extrinsic loss mechanisms in BST [19] and emerge in the case of doping with divalent or trivalent iron dopants, are either neutral (Fe Ti [20,21] the association of these defects, exemplarily shown for Fe Ti 0 , is described by Eq. 1…”