Microstructural study of nanocrystalline pure and doped tin dioxide to be used for resistive gas sensors

Nanocrystalline pure and doped SnO2 have been intensively studied for a long time to build resistive gas sensors. However, it is still useful to synthesize nanopowders with the smallest crystallite size to build devices. A modified gel-combustion method and a novel reactive oxidation process are proposed for nanopowders synthesis and results are compared. Materials have been characterized by XRD, Scherrer equation to evaluate the crystallite size; BET absorption to determine specific area and HRTEM to observe the crystallites (evaluating their mean size and distribution); defects and effect of calcination treatments are also considered. Previous studies have shown that if nano-SnO2 replaces the conventional microcrystalline-SnO2 to build resistive gas sensors, sensitivity increases (>30%) and the operation temperature considerably decreases. A heating and measuring system has been designed for achieving low power consumption and uses pulsed heating operation. This method of electrical control and measurement is operated intermittently, with “heating” and “readout” cycles (readout: signal of sensitive film).