High temperature fiber-optic evanescent wave hydrogen sensors using La-doped SrTiO3 for SOFC applications

Abstract

Advanced sensors are needed for development of nextgeneration fossil fuel power generation technologies and for enhancing efficiencies of existing power generation systems. Optical waveguidebased sensing technologies have become increasingly important for harsh environment energy applications. In this manuscript, we present sensing results for fiberoptic evanescent wave hydrogen sensors employing Ladoped SrTiO 3 layers as the active sensing element. These sensors show a rapid, reproducible sensing response to hydrogen fuel gas streams at elevated temperatures (600800 °C). The presence of hydrogen results in a reversible and reproducible decrease in nearinfrared transmission through the sensor. Sensors were also tested directly in the anode assembly of an operating solid oxide fuel cell (SOFC) with the sensor response correlating with both H 2 concentration and SOFC cell potential.

Cost-effective fabrication of polycrystalline TiO2 with tunable n/p response for selective hydrogen monitoring

“…Titanium dioxide or titania (TiO 2 ) belongs to the MOX group and exhibit not only excellent sensitivity, but stability even in harsh conditions and elevated temperatures [15][16][17][18]. It has already been experimentally proved that bulk TiO 2 , in general, exhibits n-type conductivity with electrons being dominant surface charge carriers and having ionized donors at room temperature with the density of electrons [e -] equals the density of donors N D ([e -] = N D = 10 17 -10 20 cm -3 ), small effective mass m * (~ 0.1-0.4 m e ) and mobility in the range =1-50 cm 2 /Vs.…”

“…It has already been experimentally proved that bulk TiO 2 , in general, exhibits n-type conductivity with electrons being dominant surface charge carriers and having ionized donors at room temperature with the density of electrons [e -] equals the density of donors N D ([e -] = N D = 10 17 -10 20 cm -3 ), small effective mass m * (~ 0.1-0.4 m e ) and mobility in the range =1-50 cm 2 /Vs. Depending on the circumstances, many factors can be considered to influence the charge carrier density ([e -]~10 16 -10 18 cm -3 ) and the mobility value (~10 2 -10 3 cm 2 /Vs), including grain boundaries, ionized impurities and electron-phonon interactions. For example, the grain boundaries in polycrystalline TiO 2 contain very high densities of surface states that results in depleted grains and capture (or scatter) free charge carriers to generate a potential barrier (~eV s ).…”

The influence of mechanical activation on structural evolution of nanocrystalline SrTiO3 powders

“…Materials based on strontium titanate can be found in a variety of applications, like sensors [1], catalysis [2], UV detectors [3], solar cell [4], multilayer ceramic capacitors (MLCCs) [5], etc. Strontium titanate powders are also well known photocatalysts for NO x degradation under UV light.…”

Semiconducting Metal Oxides: SrTiO3, BaTiO3 and BaSrTiO3 in Gas-Sensing Applications: A Review

“…Apart from the conventional resistive-type SrTiO 3 -based gas sensors, ST was used as a gas-sensitive layer for fiber optic evanescent-wave hydrogen sensors, where SrTiO 3 films were doped with lanthanum (La) [83]. These sensors show a rapid, reproducible sensing response to hydrogen fuel gas streams at elevated temperatures (600-800 • C).…”