Cross-sensitivity of various doped strontium titanate films to CO, CO 2, H 2, H 2O and CH 4

Abstract

Doped and undoped films made from SrTiO 3 have proved to be promising for use in high-temperature oxygen sensors (600<T<1000 °C). Studies on the cross-sensitivity of these materials constitute an important basis for understanding sensor signals. Reactive gases such as CO and CO 2 have only a reducing effect when present in concentration of 1% in oxygen-containing gas mixtures (1% O 2, the remainder being N 2).The strongest effect is seen at about 575 °C, H 2, H 2O and Ch 4 also have a reducing effect in oxygen-containing atmospheres below a temperature that is dependent on the reactive gas in question. However, above these temperatures such gases have an ‘oxidizing’ effect. These effects can be explained on the basis of a surface model for SrTiO 3 that assumes that the positive surface charge at the grain surface is at least partially counterbalanced by OH groups.