Sr(Tix, Fe1-x)O3-δ solid solutions were found to change their temperature coefficient of resistance (TCR) from negative to positive as iron increasingly substitutes for titanium, with the TCR tending towards zero at × = 0.35. This composition, Sr(Ti0.65Fe0.35)O3-δ thus shows temperature independent characteristic.
For the development of a planar type sensing element for automotive applications, Sr(Ti, Fe)O3-δ has to be applied as a thick film. To confirm the sensor characteristic temperature independence (at T = 750…950 °C, p O2 = 10−5…1 bar) and fast response times (t 90 = 6.5 ms at 900 °C), both key issues of Sr(Ti, Fe)O3-δ, thick film sensors have to be maintained over the entire lifetime. In this work, the structural and electrical properties of the sensor are investigated with regard to the chemical stability of the sensing element.