Porous ceramic sensor for measurement of gas moisture in the ppm range

A moisture sensor based on porous alumina with interdigited thick film electrodes has been designed and fabricated to detect and measure concentration of moisture in gases over a wide range. Thin alumina compacts have been taken where the surface and penetration effect has been considered during the process of adsorption and absorption of water molecules through pores and grain boundaries. The porous structure of the compacts: have been obtained by controlling the particle size of the powder taken, pore size and distribution particularly on the surface by varying the percentage of pore former and sintering temperature. The electrode screen-printed with thick film conductive pastes and the designing of the electrodes have been optimized to obtain maximum sensitivity. The sensor so obtained is basically planar, porous and is found to be sensitive in the range 50-100 ppmv level of moisture. The response time of the sensor in ppmv level is less than 4 min and at higher concentration of moisture, it shows quasi-linear dependency on moisture content. (C) 2001 Elsevier Science B.V. All rights reserved.