Titanium based material for high-temperature gas sensor in harsh environment application

High temperature gas sensors are mainly designed to solve gas detection and monitoring problems with high operating temperature environment, such as gas turbine, nuclear power plants and automobile internal combustion engine emission. Cost effective metal oxide based gas sensors operate mostly at temperatures <400 °C. There are only few reports in literature focusing on their gas sensing above 400 °C. Titanium dioxide (TiO₂) is one of them to be capable of operating at and above 600 °C. However, TiO₂ is a high resistive n-type semiconductor with relatively poor conductivity for sensing oxidative gases such as nitrogen dioxide (NO₂). This disadvantage was previously reported to be overcome through addition of low valence dopant atoms which alter the electronic structure. Another strategy is to use catalytically doped perovskite based titanium compounds such as BaTiO₃. In this work, we report synthesis of Co and Ni doped TiO₂, Rh-doped BaTiO₃ by co-precipitation method and demonstrate gas sensing ability above 500 °C. Our results yield that Co-doping of TiO₂ promotes p-type behavior exhibiting good sensing properties to NO₂ while Ni-doping displays the maintenance of n-type behavior and better H₂-sensing properties at 600 °C. More interestingly, Rh-doped BaTiO₃ shows excellent NO sensing properties even at 900 °C