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

Abstract

The present study is focused in two directions. In the first part, BaFe(1 g x) g 0.01Al0.01Tai>x/i>O3 g i/i (BFATix/i) thick films with a Ta content between 0.1 and 0.4 were manufactured using the novel room temperature coating method qaerosol deposition/q (ADM), and its material properties were characterized to find the best composition of BFATix/i for temperature-independent oxygen sensors. The material properties qSeebeck coefficient/q and qconductivity/q were determined between 600 and 800gC at different oxygen partial pressures. BaFe0.69Al0.01Ta0.3O3 g i/i (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 (ip/iO2g&gt10g5gbar), the electrical conductance of the sensor shows an oxygen sensitivity of im/ig Combining double low line g0.24 (with im/i being the slope in the logiσ/i vs. logip/iO2 representation according to the behavior of iσ/iiα/iip/iO2im/i), while the Seebeck coefficient changes with a slope of g38gμVgKg1 per decade of ip/iO2 at 700gC. However, at low ip/iO2 (ip/iO2g