The effect of relative humidity on the NO2 sensitivity of a SnO2/WO3 heterojunction gas sensor

The sensitivity of a heterojunction sensor, formed between WO3 and 3 wt.% Nd2O3 doped SnO2, to humidity and NO2 has been investigated using forward bias resistance measurements at 300degreesC. The sensor showed high sensitivity and a pseudo-linear response to NO2 in the range 0-5 ppm in dry air. The response to variations in relative humidity (RH) was small at RH levels below 40%, with the sensor becoming saturated at higher values of RH. Cross-sensitivity measurements were carried out to assess the influence of RH variations on the sensor response to 2.5 and 5 ppm NO2. Strong interference effects were observed, with the sensitivity of the sensor to NO2 decreasing rapidly as the RH of the atmosphere increased. (C) 2004 Elsevier B.V. All rights reserved.