Study of structural, optical and gas sensor properties, tin oxide nanoparticles doped with iron synthesized by microwave method

In this study, iron-doped tin oxide semiconductor nanoparticles with an iron to tin mole ratio of 0, 1, 2 and 3% synthesized by microwave method. The crystal structure, surface morphology, chemical bonds, and optical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), infrared fourier transform spectroscopy (FTIR), and UV–Vis spectroscopy. Elements analysis was performed by EDAX. The X-ray diffraction results showed that the samples were polycrystalline, and have the preferred peaks of plates (110), (101), (200), (211), (220), (002), (310), (112), and (301) SnO2 phase with rutile rectangular structure. Increasing the iron impurity density from zero to three percent causes the reducing average size of nanocrystals from 23.53 to 11.03 nm, reducing grain size from 37 to 28 nm, and increasing unit cell volume from 70.61 to 71.40  and the optical band gap from 3.3 to 4.2 eV. The results of FTIR analysis confirm the SnO2 bond in the samples. Investigation of the sensing properties of ethanol gas by the samples showed that the response time of the sensors is in the range of 15.75 to 38.85 s. The sensor made with nanoparticles with a concentration of 1% iron exhibited optimum sensing conditions.