Study of the response behavior of a CdS-SnO₂ thick film for high selectivity towards propanol gas

Gas monitoring devices are in demand for a rapidly growing range of applications. Metal oxide-based gas sensors have been extensively used for the detection of toxic pollutant gases, combustible gases, and hydrocarbon vapors. The sensitivity for a low concentration and observed response and the recovery times of the reported gas sensors are not satisfactory, and it needs further detailed studies. In the present work, undoped SnO₂ and cadmium sulfide (CdS)-doped SnO₂ thick films were fabricated using the screen-printing method to study their sensing behavior towards tested organic vapors such as acetone, propanol, and ethanol. The sensing properties of fabricated sensors were investigated for the test gases, i.e. acetone, propanol, and ethanol, at an elevated temperature of 473 K. It was observed that the 2 wt% CdS-doped SnO₂ sensor showed a maximum response (78%) and was highly selective (44.6%) to propanol over acetone and ethanol. The results showed that the diminution of the SnO₂ crystallite size with the CdS content leads to an improvement in the response of the SnO₂ sensor for the tested gases. The microstructural properties are also correlated to the sensing behavior. The measurement showed that the CdS-SnO₂ thick film sensor is highly sensitive. At the same time, it is more selective to propanol than the other test gases, ethanol and acetone.