Combined resistive and thermoelectric oxygen sensor with almost temperature-independent characteristics

Bektas, Murat; Stöcker, Thomas; Mergner, Angelika; Hagen, Gunter; Moos, Ralf

The present study is focused in two directions. In the first part, BaFeinline-formula M1inlinescrollmathml ( normal 1 - x ) - normal 0.01 44pt9ptsvg-formulamathimg4324a5cde868890cf7c7304df3a26029 jsss-7-289-2018-ie00001.svg44pt9ptjsss-7-289-2018-ie00001.png Alinline-formula0.01Tainline-formulaxOinline-formula3−δ (BFATinline-formulax) thick films with a Ta content between 0.1 and 0.4 were manufactured using the novel room temperature coating method “aerosol deposition” (ADM), and its material properties were characterized to find the best composition of BFATinline-formulax for temperature-independent oxygen sensors. The material properties “Seebeck coefficient” and “conductivity” were determined between 600 and 800 inline-formulaC at different oxygen partial pressures. BaFeinline-formula0.69Alinline-formula0.01Tainline-formula0.3Oinline-formula3−δ (BFAT30) was found out to be very promising due to the almost temperature-independent behavior of both the conductivity and the Seebeck coefficient. In the second part of this study, films of BFAT30 were prepared on a special transducer that includes a heater, equipotential layers, and special electrode structures so that a combined direct thermoelectric/resistive oxygen sensor of BFAT30 with almost temperature-independent characteristics of both measurands, Seebeck coefficient and conductance could be realized. At high oxygen partial pressures (inline-formulapOinline-formula2 > 10inline-formula−5 bar), the electrical conductance of the sensor shows an oxygen sensitivity of inline-formulaminline-formula= 0.24 (with inline-formulam being the slope in the loginline-formulaσ vs. loginline-formulapOinline-formula2 representation according to the behavior of inline-formulaσαpOinline-formula M22inlinescrollmathml normal 2 m 9pt15ptsvg-formulamathimg8de9585e1d3b7707bba563c39a89ec18 jsss-7-289-2018-ie00002.svg9pt15ptjsss-7-289-2018-ie00002.png ), while the Seebeck coefficient changes with a slope of inline-formula−38 inline-formulaµV Kinline-formula−1 per decade of inline-formulapOinline-formula2 at 700 inline-formulaC. However, at low inline-formulapOinline-formula2 (inline-formulapOinline-formula2 < 10inline-formula−14 bar) the conductance and the Seebeck coefficient change with inline-formulapOinline-formula2, with a slope of inline-formulaminline-formula=inline-formula−0.23 and inline-formula−21.2 inline-formulaµV Kinline-formula−1 per decade inline-formulapOinline-formula2, respectively.

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Bektas, Murat / Stöcker, Thomas / Mergner, Angelika / et al: Combined resistive and thermoelectric oxygen sensor with almost temperature-independent characteristics. 2018. Copernicus Publications.

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