PERFORMANCE OF PROTECTED OXYGEN SENSORS .1. SINGLE-PHASE MIXED CONDUCTING FILTERS

Theoretical predictions on sensor performance are compared with experi mental data obtained for YSZ (yttria stabilized zirconia) sensors prot ected by different types of single phase mixed conductors, including m aterials usually identified as predominantly ionic or electronic condu ctors. Relevant parameters determining the protected sensor performanc e are the ratio between the sensor and the filter oxygen electrochemic al permeabilities, the volume of the electrode protection chamber, the temperature and the magnitude of the oxygen pressure being measured. The sensor to filter electrochemical permeability ratio determines the steady state deviation between the protected and unprotected sensor r eading. Decreasing the protected chamber volume and the magnitude of t he oxygen partial pressure being measured will determine a faster sens or response. Results now reported, corresponding mostly to slow sensor response, are strongly determined by the relatively low operating tem peratures (850-950 degrees C) used in these laboratory scale experimen ts, but can be optimized for industrial applications.