PERFORMANCE EVALUATION OF SOX (X=2,3) GAS SENSORS USING AG-BETA''-ALUMINA SOLID-ELECTROLYTE

Fully solid state SOx sensors have been investigated with a galvanic c ell of Pt, Ag/Ag-beta ''-alumina/SO3, SO2, O-2, Pt using tubular Ag-be ta ''-alumina as solid electrolyte, metal silver as solid reference el ectrode, and porous Pt as working electrode. The values of electric mo tive force (EMF) of the sensors are consistent with the theoretically calculated ones at temperatures above 550 degrees C in the p(SOx) rang e of at least 10-50 000 ppm. Applying catalysts such as Pt-net and V2O 5 in the gas upstream considerably improves the sensor performance and extend its working temperature down to 450 degrees C. The reproducibl e EMF values are obtained in the gas flow velocity of 0.2-0.4 cm/s. Th e response time of the sensors is 50-100 s as the p(SOx) changes. The sensors exhibit a good selectivity to SOx against hundred-fold concent rations of CO2, NO2 and H2O.