CHARACTERIZATION OF STRONTIUM CONTAINING TIN DIOXIDE-BASED THICK-FILMHUMIDITY SENSORS

Humidity is an important process parameter in a variety of industrial and agro-industrial processes. Ceramic based humidity sensors find an application in these domains where relatively high humidity levels are frequently encountered. Humidity sensitive materials based on tin dio xide, strontium carbonate and zinc borosilicate mixtures are used to p repare precursor powders for thick film humidity sensors. The response s of sensors based on well defined ink formulations are analysed by im pedance spectroscopy. The influence of composition of the sensing mate rial and operating frequency is studied in order to obtain optimum sen sing conditions at room temperature. Over the range of compositions st udied the sensor materials show an appreciable variation in humidity s ensitivity, film adhesion, optimum operating frequency, etc. It is con cluded that notwithstanding a drastic increase in sensitivity due to t he addition of zinc borosilicate, sensor materials containing approxim ately equal weights of tin dioxide and strontium carbonate show the be st acceptable overall properties for sensor applications in relatively humid environments.