A NOx Sensor Based on Solid-Electrolyte Impedance Transducer

A new solid-electrolyte impedance-metric NOx sensor device composed of a lithium ionic solid electrolyte: Li1.5Al0.5Ti1.5(PO4)3 (LATP) as a transducer and ceramic oxides (perovskite-type oxides, TiO2, SnO2, etc) as a receptor, respectively, have been systematically investigated for the detection of NOx (NO and NO2 ) in the range 10 – 200 ppm at 400 - 500ºC. Responses of the sensors were able to divide component between resistance and capacitance, and it was found that the device was applicable to the selective detection of NO or NO2 concentration in each ingredient. Especially, those using TiO2, SnO2 (n-type semiconductor) and perovskite-type oxides (LaCoO3, LaNiO3 and LaCrO3) based receptors gave good responses to NO and NO2. It was also found that the responses were different between n-type or p-type semiconductors, in which we tried to elucidate the sensing mechanism