High temperature oxygen sensors based on doped SrTiO3

The sensor properties of semiconducting strontium titanate can be modified by dopants. On the one hand, the ambiguous dependence of the electrical con ductivity on the oxygen partial pressure can be changed by a small lanthanu m (donor) concentration to an unambiguous one over a wide oxygen partial pr essure range. Polycrystalline Sr0.995La0.005TiO3 and/or thick films have re sponse times of few milliseconds, caused by a surface type mechanism of the conductivity. The bulk type mechanism is very slow and is responsible for the long-term behaviour. On the other hand, the temperature dependence of s trontium titanate can almost be suppressed for a small oxygen partial press ure range by a high iron (acceptor) content. On the basis of SrTi0.65Fe0.35 O3 a fast thick film oxygen sensor is proposed, which can be applied to con trol of lean-bum engines. (C) 1999 Elsevier Science S.A. All rights reserve d.