A NOVEL TEMPERATURE-GRADIENT NA+-BETA''-ALUMINA SOLID ELECTROLYTE BASED SOX GAS SENSOR WITHOUT GASEOUS REFERENCE ELECTRODE

An electrochemical SOx ps sensor with a tubular Na+-beta"-alumina solid electrolyte has been fabricated and tested under non-isothermal conditions. The temperature difference between the reference and working electrode of the sensor cell is about 100-degrees-C, which causes a serious deviation of the experimental EMF response from the value as calculated using the Nernst equation for an isothermal system. The experimental results are Consistent with the theoretical prediction for a non-isothermal system. The response time is usually less then 10 min. SEM and EDX have been employed to investigate the sensor material before and after use, confirming the formation of a glassy phase of Na2SO4 by an electrochemical reaction at the interface of the platinum electrodes and Na+-beta"-alumina. According to this new theoretical derivation, the sensor design could be simplified by applying the same SO2 ps at the two electrodes. The EMF of this so-called TGNB (Temperature Gradient Na+-beta"-alumina) SOx sensor is in good agreement with the theoretical prediction. The consistence of the experimental results with the theoretical values and the simple construction of this type of SOx sensor indicate its potential applicability.