Lanthanum doped tin oxide: Synthesis, characterization and application

This paper describes the synthesis of La-doped SnO2 nanoparticles for resistive-type relative humidity sensors. The structural characterization of synthesized SnO2 nanoparticles was analyzed using X-ray Diffraction (XRD), that exhibited the formation of the tetragonal rutile structure of pristine and La-doped SnO2 nanoparticles with a decrease in crystallite size in presence of different doping levels. Further increase in doping concentration (at 5 M%) revealed the formation of the La2O3 phase due to the excess amount of lanthanum. The UV–Vis spectroscopy indicates the doping of lanthanum (La) improves the optical property of pristine SnO2. The morphological characterization demonstrates the spherical-shaped nanoparticles. The synthesized nanoparticles were tested for relative humidity (RH) sensing application over the range of 10–100% RH at room temperature. The doping of 3 M% La-doped SnO2 shows good sensitivity (95%) than pristine SnO2 nanoparticles. The fabricated 3 M% La-doped SnO2 sensor not only showed better sensitivity and linear range over 10–100%RH, but also exhibited rapid response (8sec) and recovery (13sec) time than the pristine and the others La-doped levels of SnO2 nanoparticles. This better humidity sensing response of 3 M% La-doped nanoparticles was achieved due to high carrier density and small crystallite size. This indicates 3 M% La-doped nanoparticles is a promising material for room temperature humidity sensing.