Crystal lattice spacing shrinkage and band-gap narrowing phenomena in In-doped SnO2nanoparticles

Pure and In-doped Tin Oxide (SnO2) nanoparticles with different doping concentration were prepared by hydrothermal method. The prepared samples were characterized by XRD, TEM, and UV–vis absorption spectroscopy. The crystal lattice spacing of In-doped SnO2 nanoparticles decreases compared with pure SnO2. The crystal lattice spacing ratios for (110), (101) and (211) crystal face shrinks acutely with 1.9% doping in SnO2. Crystallite size calculated by the FWHM of the first major XRD peaks (110) decreases from 3.945 to 3.281 nm as the doping concentration increases from 0 to 10%, whereas the strain increases. XRD study reveals that crystal lattice spacing of SnO2 nanoparticles shrinks due to the effect of In element doping. Optical band-gap of SnO2 nanoparticles decreases from 3.76 to 3.33 eV first, and then increases to 3.55 and 3.52 eV, respectively, as the doping concentration changes from 1.9, 3.8 to 10%. Band-gap narrowing originates from the effect of crystal lattice spacing shrinkage.