SOLID ELECTROLYTE NO2 SENSORS FITTED WITH SODIUM-NITRATE AND OR BARIUM NITRATE ELECTRODES

Solid electrolyte-based electrochemical elements fabricated with beta/beta" -alumina (and NASICON) and nitrate electrodes were tested for the detection of NO2 in the range 10-200 ppm. The element fitted with an NaNO3 sensing electrode exhibited excellent performance for the potentiometric sensing of NO2 at 200-degrees-C, but its operation was limited up to the melting point of NaNO3 (307-degrees-C). The use of a binary nitrate electrode of Ba(NO3)2-NaNO3 made it possible to stand operation at higher temperature up to 500-degrees-C without deteriorating the sensing performance. A Ba(NO3)2 electrode, when combined with a barium-ion conductor, was found to give excellent NO2 sensing properties. A possibility of the amperometric sensing of NO2 was also demonstrated experimentally.