Optical Transmittance of Thin Films of SrFeO2.5+x at Elevated Temperatures and Applications to Gas Sensing

Abstract

AbstractNon-stoichiometric perovskites with the general formula SrFeO2.5+x have potential in oxygen sensing applications. Thin films of these compositions have been grown onto various substrates by pulsed laser deposition techniques. At elevated temperatures, (T > 550K), the films react rapidly and reversibly with oxygen and the bulk oxygen content, x, of the films changes. Accompanying the change in oxygen stoichiometry are significant changes in the optical transmittance and reflectance of the films. Transmission spectrophotometry in the uv-vis region has been used to determine the relationship of transmittance with oxygen composition in the gas phase. Spectrophotometric data have been obtained by a batch method and also in-situ in a flow cell at T = 690K. The data show a large variation in transmittance, exceeding 103 for the batch measurements, with SrFeO3 showing the highest opacity. The design of the flow cell is also described.