Temperature drop of semiconductor gas sensor when exposed to reducing gases — simultaneous measurement of changes in sensor temperature and in resistance

Changes in sensor temperature, ΔT, and in semiconductor resistance, ΔR, were simultaneously measured when various semiconductor gas sensors were exposed to reducing gases. The drop of the sensor temperature was often observed, together with a decrease in semiconductor resistance, despite the exothermic reaction of the gases with the surface oxygen adsorbates. As a plausible explanation for this phenomenon, it was considered that the temperature drop was caused by a change in thermal conductivity of the sensors, as a result of an increase in the amount of conduction electrons due to consumption of negatively charged oxygen ad-ions.