Characteristics of high sensitivity ethanol gas sensors based on nanostructured spinel Zn sub(1&; minus; xCo) sub(x)Al sub(2O) sub(4)

Nanocrystalline powders of Zn sub(1) sub(-)xCo sub(xAl) sub(2)O sub(4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) mixed oxides, with cubic spinel structure were successfully prepared by the ethylene glycol mediated citrate sol-gel method. The structure and crystal phase of the powders were characterized by X-ray diffraction (XRD) and microstructure by transmission electron microscopy (TEM). X-ray diffraction results showed that the samples were in single phase with the space group Fd-3m. TEM analysis showed that the powders with spherical shape were uniform in particle size of about 17-24 nm with mesoporous in nature. Further investigations were carried out by FT-IR. Thick films of as-prepared Zn) sub(1) sub(-xCo) sub(x)Al sub(2O) sub(4) powders were fabricated using screen-printing technique. The response of Zn sub(1) sub(-)xCo sub(xAl) sub(2)O sub(4 based thick films towards different reducing gases (liquefied petroleum gas, hydrogen, hydrogen sulfide, ethanol gas and ammonia) was investigated. The sensor response largely depends on the composition, temperature and the test gas species. The Co (cobalt) content has a considerable influence on the gas-sensing properties of Zn) sub(1) sub(-xCo) sub(x)Al sub(2O) sub(4). Especially, Zn sub(0.4Co) sub(0).6Al sub(2O) sub(4) composition exhibited high response with better selectivity to 100 ppm C sub(2H) sub(5)OH gas at 150 degree C. The instant response (~7 s) and fast recovery (~16 s) are the main features of this sensor.