Effect of Co on the magnetic and gas sensing properties of SnO2 nanoparticles

Abstract

Undoped and Co-doped (0.5 and 3 at. %) SnO2 nanoparticles were synthesized by the co-precipitation method and the structural characterization done by X-Ray diffraction revealed the tetragonal rutile structure with a weak CoO phase in 3 at. % Co-doped sample. TEM and high-resolution transmission electron microscope images of Co-doped (3 at. %) SnO2 nanoparticles showed the presence of almost spherical nanoparticles with the particle size in the range of 7–9 nm. Pure SnO2 showed mixed phases of ferro and diamagnetism while Co-doped (3 at. %) SnO2 nanoparticles showed only ferromagnetism at room temperature. The room temperature ferromagnetism (RTFM) in the Co-doped sample is due to the interaction of the localized spins of the Co ions with the oxygen vacancies, which are introduced due to the substitution of Co2+ ions for Sn4+ ions (bound magnetic polarons). The presence of oxygen vacancies and the small particle size are responsible for the slightly enhanced ethanol sensitivity of Co-doped (3 at. %) SnO2 nanoparticles compared to SnO2 nanoparticles. From the results, it is concluded that the nanoparticles showing RTFM have potential applications in detecting ethanol.