INFLUENCE OF MICROSTRUCTURES ON THE FUNCTIONAL-PROPERTIES OF TIN OXIDE-BASED GAS SENSORS

Three types of SnO2 sintered-pellet gas sensors with different relative densities ranging between 0.5 and 0.3 and with almost equal grain and neck sizes have been prepared and tested. The influence of such microstructures on the functional properties of SnO2 gas sensors has been investigated using dry air and 1000 ppm ethanol in air, over the temperature range 600-700 K. Experimental data are discussed in the light of existing theories. Different equations for the sensitivity have been rewritten and discussed in order to separate the contribution of the microstructure from other contributions. The equations allow one to understand the sensitivity behaviour versus temperature and applied external electrical field. Furthermore, such equations predict the effects of the average coordination number on the electrical sensitivity of the three families of sensors, in significant agreement with the experimental data.