Optical and Chemi-Resistive Sensing in Extreme Environments: La-Doped SrTiO₃ Films for Hydrogen Sensing at High Temperatures

For efficient operation of next-generation fossil fuel technologies, development of sensors capable of withstanding harsh environments is required. Optical waveguide based sensing platforms have become increasingly important, but a need exists for materials that exhibit useful changes in optical properties in response to changing gas atmospheres at high temperatures. In this manuscript, the onset of a near-IR absorption associated with an increase in free carrier density in doped metal oxide films to form so-called conducting metal oxides is discussed in the context of results obtained for undoped and La-doped SrTiO 3 films. Film characterization results are presented along with measured changes in optical absorption resulting from various high temperature treatments in a range of gas atmospheres. Optical property changes are also discussed in the context of a simple model for optical absorption in conducting metal oxide thin films. The combination of experimental results and theoretical modeling presented here suggests that such materials have potential for high temperature optical gas sensing applications. Simulated sensing experiments were performed at 600–800 °C, and a useful, rapid, and reproducible near-IR optical sensing response to H 2 confirms that this class of materials shows great promise for optical gas sensing.