Tuning of the electrical conductivity of Sr(Ti,Fe)O3 oxygen sensing films by aerosol co-deposition with Al2O3

Iron-substituted strontium titanate Sr(Ti,Fe)O3 (STF) is a semiconducting oxygen sensing ceramic, and features a temperature independent conductivity at temperatures between 700 and 800 °C for the composition SrTi0.65Fe0.35O3–δ (STF35). Aerosol deposition (AD) offers advantages as a means of producing thick films of this sensor material. In this work, aerosol co-deposition of ceramics (AcDc) was used to tune the functional properties of STF35 by incorporating alumina particles directly. Composite films of STF35:Al2O3 with homogeneously distributed particle fractions were successfully deposited by AcDc. The conductivity of films was tunable over an order of magnitude with up to 60 volume percent alumina, and the temperature independent oxygen sensing behavior, as observed in bulk ceramics, was retained. Higher percentages of alumina decreased the conductivity further (up to four orders of magnitude) but the sensor response characteristic to oxygen disappeared.