The impact of UV irradiation on Fe-doped SrTiO 3 (Fe:STO) single crystals is investigated at elevated temperatures. Illumination leads to incorporation of oxygen into the single crystals and thus to a decreasing oxygen vacancy concentration and oxidation of Fe 3+ to Fe 4+ . The Fe 4+ ions cause a color change from transparent/brownish to black. This photo chromic blackening due to stoichiometry changes at elevated temperatures is irreversible at room temperature, but annealing at high temperatures, for example at 700 °C, can restore the original stoi chiometry and color. Absorbance changes due to UV irradiation are monitored by ex situ and in situ UV-vis spectroscopy experiments and changes in electrical properties are measured by van der Pauw measurements and in-plane electrochemical impedance spectroscopy. After 1140 min of illumination at 440 °C, for example, electrical measurements reveal a conductivity increase by more than a factor of 5 due to the enhanced hole concentration in blackened Fe:STO. In addition, UV illumination increases the oxygen chemical potential up to a calculated p(O 2 ) of more than 10 9 Pa in Fe:STO. Hence, UV light can be used to tune the color, but also electrical properties of Fe:STO by directly impacting the bulk defect concentrations.

The interplay of structure, composition and electrical conductivity was investigated for Fe-doped SrTiO3 thin films prepared by pulsed laser deposition. Structural information was obtained by reciprocal space mapping while solution-based...

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The possibility to control oxygen transport in one of the most promising solid oxide fuel cell cathode materials, La 0.6 Sr 0.4 CoO 3−δ , by controlling lattice strain raises questions regarding the contribution of atomic scale effects. Here, high-resolution transmission electron microscopy revealed the different atomic structures in La 0.6 Sr 0.4 CoO 3−δ thin films grown under tensile and compressive strain conditions. The atomic structure of the tensile-strained film indicated significant local concentration of the oxygen vacancies, with the average value of the oxygen non-stoichiometry being much larger than for the compressive-strained film. In addition to the vacancy concentration differences that are measured by isotope exchange depth profiling, significant vacancy ordering was found in tensile-strained films. This understanding might be useful for tuning the atomic structure of La 0.6 Sr 0.4 CoO 3−δ thin films to optimize cathode performance.