HUMIDITY-SENSING BEHAVIOR OF SURFACE-MODIFIED ZIRCONIA

The humidity-sensing properties of one of the most well-known solid su peracids, namely, sulfated zirconia, have been systematically investig ated in order to correlate the mechanism of humidity sensing with the strength and distribution of acid sites on the surface. The surface-mo dified zirconia shows an unprecedented resistance change (10(11) to 10 (4) Ohm) with change in the relative humidity with a superior slope il lustrating better sensitivity compared to normal ceramic oxides. Measu rements of adsorption enthalpy for surface-modified and conventional z irconia indicate an energetically favourable interaction of water vapo ur with the oxide surface in the presence of sulfate species. Morpholo gical characterization using scanning electron microscopy reveals the importance of particle size and surface texture in controlling the hum idity-sensing behaviour. In addition, physicochemical characterization techniques like X-ray diffraction and IR spectroscopy have confirmed the role of sulfur species on the surface in causing the high humidity sensitivity.