Thin films of [alpha]-Mn.sub.2O.sub.3 for resistance-based sensing of acetaldehyde vapor at ambient temperature

Thin films of dimanganese trioxide ([alpha]-Mn.sub.2O.sub.3) were deposited on glass substrates by using manganese acetate tetrahydrate as the precursor salt and spray pyrolysis technique. X-ray diffraction patterns of the film indicate a polycrystalline nature and a cubic crystal structure. Field-emission scanning electron micrograph and transmission electron micrograph reveals the formation of spherical nanocrystallites along with pores with sizes of 10 ± 5 nm. The electrical resistance of the film drops on exposure to vapours of acetaldehyde at ~30 °C. The sensor covers the 5 to 75 ppm concentration range, displays fast response (9 s) and recovery (~35 s), and is fairly selective over acetone, ammonia, formaldehyde, benzene, water vapour and ethanol.