Stable and selective sulfur dioxide sensing elements operating at 800–900 centigrade

Sensing behavior of electrochemical transducers for the detection of sulfur dioxide (SO2) is described. These elements operate at temperatures in the range 800-900 °C, and are constructed from oxide and precious metal electrodes on oxygenion conducting substrates. The responses to SO2 at oxygen contents around 5% can be large, with 25 ppm SO2 causing a 30-40% change in the sensing signal. This SO2 response is shown to be little affected by oxides of nitrogen (NOx), carbon monoxide, and propylene, present at the 100s of ppm level. Element stability is demonstrated over about 50 days of operation at temperature.