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Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)Osub3-x/sub thin film case study

机译:氧表面交换动力学通过同时光传输弛豫和阻抗光谱测量:Sr(Ti,Fe)O 3-x /亚>薄膜壳体研究

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摘要

We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTisub0.65/subFesub0.35/subOsub3-x/sub film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fesup4+/sup) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The ksubchem/sub values obtained by OTR were significantly lower than the AC-IS derived ksubchem/sub values and ksubq/sub values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in ksubchem/sub and ksubq/sub values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived ksubchem/sub values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.
机译:通过同时光传输弛豫(OTR)和交流阻抗光谱(AC-IS),比较测量氧表面交换动力学的方法,在相同的混合传导SRTI 0.65 FE 0.35 O 3-x 膜。在薄膜中作为氧气活性的函数评价表面交换系数,通过施加在离子传导ytTria稳定的氧化锆基底上的含油部分压力和/或DC偏压。通过薄膜随时间(弛豫)的测量光传输的变化由对应于其氧气和氧化Fe的变化(〜Fe 4 + )浓度的薄膜中的光学吸收变化产生;通过适合于薄膜几何形状的表面交换限制动力学的等式成功地描述了这种弛豫型材。通过OTR获得的K <亚>化学值显着低于AC-in衍生的k 化学值和k q 值乘以热力学因子(散装或薄膜),暗示金属集电器(PT,AU)的k中可能的增强。通过AC-IS获得的K Chem 和k Q / sub>值的长期降解也归因于多孔PT电流集电器的劣化,而在此期间没有观察到显着降解光学衍生的k chem 值。结果表明,虽然集电器可能会通过AC-IS对测量影响测量,但OTR方法提供连续,原位和无联接方法,以测量薄膜的天然表面的氧气交换动力学。

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