Stabilized zirconia-based sensor using oxide electrode for detection of NO sub(x) in high-temperature combustion-exhausts

New type NO sub(x) sensors were newly designed by using stabilized zirconia and an oxide sensing electrode. Among the various oxides examined for the sensing electrode, CdMn sub(2)O sub(4) was found to be the most excellent material. Both planar and tubular devices attached with a sputtered CdMn sub(2)O sub(4) layer could respond well to NO sub(2) as well as NO in air at higher temperature, such as 500 degree C. The EMF values of the devices were almost linear to the logarithm of NO sub(x) concentration with a positive slope for NO sub(2) and a negative slope for NO. A NO sub(x) sensing mechanism involving mixed potential was proposed based on the measurements of polarization curves.