Characteristics of Limiting Current‐Type Oxygen Sensor

Abstract

Characteristics of oxygen sensors based on limiting current behavior of zirconia pumping cells have been investigated. To limit oxygen transport from ambient gas to the cathodes of the zirconia pumping cells, a drilled cover and a porous layer were examined. For the sensor with a diffusion hole of the drilled cover, the limiting current showed a considerable nonlinearity to oxygen concentration in a high oxygen concentration and a temperature dependence as T "~ in oxygen-nitrogen mixtures. This behavior is in good agreement withthat expected from a model in which the oxygen transport rate is limited by the diffusion hole. For the sensor with the porous layer, the sensor output indicated a weak temperature dependence and good linearity to oxygen concentration compared with the former sensor. These characteristics can be explained by taking into account the fact that the oxygen diffusion in the porous layer involves both the Knudsen and ordinary molecular diffusion mechanisms.Social demands for research to improve fuel efficiency and reduce the amount of pollutant exhaust emissions of automobiles are increasing. To achieve both objectives simultaneously--the improvement of fuel efficiency and the reduction of the exhaust emissions--it is well known that the employment of fuel:lean combustion is quite effective in an internal combustion engine. For the internal combustion engine, the fuel efficiency becomes higher as the magnitude of specific heat ratio, C,,/Cv, of the combustion gas in the engine cylinders is larger, where C,, and C,. are the specific heat at constant pressure and volume, respectively. The ratio CJC, for air is about

Miniature Nernstian oxygen sensor for deposition and growth environments

“…Both use stabilized zirconia as the oxide ion conducting solid electrolyte and operate at elevated temperatures 800-1000°C. The first kind is a limiting current-type sensor 7,8 which operates on the principle of diffusion limited current induced by the viscous flow of molecular oxygen through a small circular aperture from the measuring environment into a ceramic cavity that employs a stabilized zirconia solid electrolyte. This sensor has a linear response with respect to oxygen content but suffers considerably from interference effects from other oxygen containing chemical constituents in the environment.…”

New Method to Fabricate Limiting‐Current‐Type Oxygen Sensors

“…Normal diffusion is generally observed in oxygen sensors with a single, large hole-type diffusion barrier, 3 and Knudsen diffusion is observed in sensors with a porous-body-type diffusion barrier in which the small-pore channels act as the gas-diffusion path. 9 Therefore, the results shown in Fig. 6 indicate that gas diffusion through the hole made by the burnout of carbon fiber in this study was virtually the rate-controlling step in the oxygen sensing.…”

Oxygen sensors based on SrTi0.65Fe0.35O3−δ thick film with MgO diffusion barrier for automotive emission control

“…In the fuel-lean region, A/F > (A/F) stoich , traditional ZrO 2 oxygen sensors show poor response. To solve this problem, limiting current oxygen sensors [23] were developed. However, the limiting current oxygen sensors can only be used in the fuel-lean region, because the signal is ambiguous in the stoichiometric A/F mixture and fuelrich region.…”