D.W. Zeng

SYNTHESIS AND GAS SENSITIVITY OF IN-DOPED ZNO NANOPARTICLES

Undoped and In-doped ZnO nanoparticles were produced by renovated hybrid induction and laser heating (HILH) in this study from Zn–In alloy, with different mole ratios, as the raw material in a flowing mixed gas atmosphere of Ar+O2. The morphological characteristics, phase microstructure, and chemical state of In-doped ZnO nanoparticles were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The change in electrical resistance of thick film based on the In-doped ZnO nanoparticles and their gas sensitivities to volatile organic compounds (VOCs), benzene, acetone, ethyl alcohol, toluene, and xylene, as a function of temperature were measured in the temperature range of 200–500 °C, and compared with the undoped thick film. The results showed that the In-doped ZnO has lower resistance and higher sensitivity than that of the undoped ZnO. This was probably due to the fact that the In3+ ions, replacing the Zn2+ ions in the ZnO lattice, resulted in an increase of the concentration of free electrons followed by an increase of the adsorbed oxygen. Among the types of In-doped ZnO, 4.58 at % In-doped ZnO had the lowest resistance, and had the highest sensitivity. On increasing the concentration of In into ZnO, its resistance increased, while the sensitivity decreased. The sensitivity of the 4.58 at % In-doped ZnO to VOCs was in the order of acetone>alcohol>xylene>toluene> benzene at an operating temperature of 420 °C.

Characteristics of Sb2O3 nanoparticles synthesized from antimony by vapor condensation method

Abstract Sb 2 O 3 nanoparticles with an average size of approximately 80 nm were synthesized by vapor condensation method. The characteristics were investigated by means of TEM, XRD, differential thermal analysis (DTA), X-ray photoelectron spectrometer (XPS) and Raman spectroscopy. The exothermic peak temperature for the nanopowder is lower than that of the micropowder, its reactive temperature span is narrower and oxidizing exothermic heat is larger due to the nano-sized effect. XPS analysis shows that a few amount of antimonies are still in metallic states as the interstitial antinomy atoms in the nanoparticles. The interstitial atoms may be mainly responsible for the red shifts (3–6.4 cm −1 ) of the characteristic peaks in the Raman spectrum.