Many industrial, aerospace, and energy applications operate at elevated temperatures (often 500 to 1000°C) as well as in chemically harsh, highly oxidizing or reducing atmospheres. By monitoring atmospheric gas compositions during operation, process controls can be optimized to improve efficiency and longevity of equipment. SAW sensors are micro transponder devices that work well in extreme temperatures and offer real-time monitoring of temperature, strain, gas composition, and more. They operate wirelessly and without batteries. The device's frequency/phase depends on the gas sensing film's electrical conductivity. However, device sensitivity to film conductivity exists only over a specific and narrow range of conductivities. Out-of-range film conductivities and insignificant conductivity responses to relevant gas/temperature conditions generally limit the success for any standard metal oxide used as a gas sensing material on SAW gas sensors. That makes them of use only in restricted gas/temperature conditions. This innovation represents a way to achieve tunable absolute conductivity of gas sensing materials by using conducting metal oxides (CMOs), which enables a SAW device to be tuned to select gas conditions and temperatures.
