SENSITIVITY, RESPONSE AND RECOVERY-TIME OF SNO2 BASED THICK-FILM SENSOR ARRAY FOR H-2, CO, CH4 AND LPG

This paper deals with the studies carried out on sensitivity, response and recovery time of a sensor array comprising of undoped and doped ( palladium, platinum and gold) thick-film SnO2 sensors. Initially, the sensitivity of all the sensors of the array has been studied for H-2, CO, CH4 and LPG followed by detailed analysis of transient response of Pd-doped sensors as it possesses better sensitivity for all the test gases. The response and recovery time of the Pd-doped sensor has been found to depend on type of gas and its concentration (upto 400 ppm). T he response time is minimum for CO and maximum for H-2 while recovery time is maximum for LPG and approximately same for H-2 and CO. The obs erved results of response time have been explained on the basis of two -film theory, i.e. gas film-gas phase and solid-gas film interfaces. F urther, the experimental result of the sensor array (sensitivity versu s concentration and sensitivity versus response time) for all the test gases at an operating temperature of 350 degrees C have been validate d with an analytical model and the observed results are found to be in good agreement to that predicted by the model. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.