Progress in the development of zirconia gas sensors

The development of zirconia gas sensors, arising from work instigated by Brian Steele in 1983, is reviewed and progress reported. New oscillatory modes of operation of pump-gauge sensors are described with concomitant advantages including, in particular, tolerance to leakage due to deterioration of the seal. A double chamber sensor, which does not need the provision of a reference gas of fixed composition, has been developed allowing the excess-air and fuel-rich regions to be distinguished in a combustion system. Planar thick-film sensors have been prepared and tested which operate effectively in the amperometric mode. Reducing unit cost is a crucial factor in the commercialisation and widespread application of these sensors and associated instrumentation.