Lithium ferrite for gas sensing applications

Microstructure and gas sensing properties of pure and samarium-substituted lithium ferrites, Li0.5SmxFe2.5−xO4 (x = 0, 0.05, 0.1 and 0.2), prepared by sol–gel self-combustion were studied. Ethanol, methanol, LPG and ammonia were used as test gases. SEM investigation evidenced that Sm ions induced microstructural changes of the Li ferrite. The finest granulation (about 100 nm) and highest porosity (44%) were observed in Li0.5Sm0.2Fe2.3O4. The gas response measurements evidenced that it depended on the working temperature and gas type. All ferrites were sensitive to alcohol (ethyl and methyl) and less sensitive to ammonia and LPG. The best responses, over 85%, were obtained at operating temperatures of 340–355 °C to ethanol and methanol vapour.