Oxygen sensors based on SrTi0.65Fe0.35O3−δ thick film with MgO diffusion barrier for automotive emission control

Oxygen sensors based on SrTi0.65Fe0.35O3−δ (STF35) thick films were fabricated by screen printing on Al2O3 substrates. STF35 nano-powder with an average crystallite size of ∼37.5 nm was used to prepare the precursor, and a MgO diffusion barrier was inserted between the STF35 film and the Al2O3 substrate to prevent the chemical diffusion and reaction. The STF35-based oxygen sensor demonstrated good performances: the temperature coefficient of resistance (TCR) was 200 ppm/K, the sensitivity (defined as S = − d log(R)/d log(pO2)) was 0.23, the response time was 100 ms at 900 °C, and the sensor's selectivity to oxygen was pretty good in the temperature range of 725–925 °C. In the same temperature range, the sensor showed only very poor sensitivity to CO and NO.