Microcharacterisation and gas sensing properties of mechanochemically processed nanosized iron-doped SnO2

SnO₂ nanoparticles, undoped and doped with 1, 2 and 5 mol% Fe₂O₃, were synthesised by mechanochemical processing. XRD analysis, for heat treatment at 600°C, revealed the average crystallite size to decrease progressively from 9.5 nm for undoped SnO₂, to 5.3 nm for SnO₂ doped with 5% Fe₂O₃. HRTEM imaging revealed the presence of a number of crystal defects. Thin films for electrical characterisation were prepared by spin coating and subsequent annealing, with the response to O₂ measured. The resistance increased for increasing dopant concentration. The response to 1000 ppm, 1% and 10% O₂ was measured, with the highest response found for the 2%-doped sample. The 5%-doped sample exhibited a weak p-type response at 400°C and below, with a transition to n-type at 450°C. The thin films prepared from the Fe₂O₃-doped SnO₂ nanopowders have potential for the development of gas sensors.