HIGH PRECISION GAS SENSORS BUILT WITH CERAMIC NANOFILMS

MARIANA P. POIASINA; NOEMÍ E. WALSÖE DE RECA; VICTOR M. WITTEMBERG; MARIO F. BIANCHETTI; HÉCTOR LACOMI; CRISTIAN L. ARRIETA

Ciudad Autónoma de Buenos Aires

Congreso; XXXI Congreso Argentino de Quimica; 2016

Asociación Química Argentina (AQA)

ABSTRACTThe semiconductor metallic oxides, like pure or doped SnO2, have been intensively used to build resistive gas sensors to detect toxic, fuel or explosive gases: NOx, SO2, CO, H2, CH4 or VOCs (Volatile Organic Compounds). SnO2, gas sensors (as based on microcrystalline materials) have been considered by its high sensitivity and relatively low operation temperature Top=350oC-450oC. If conventional microcrystalline SnO2 is substituted by nanocrystalline SnO2 to build the sensors, the authors have proved that sensor sensitivity increases from 30% to 35% and the Top decreases from (350-450)ºC to a range (180-220)ºC. In the last decade, nanocrystalline powders with high [surface/volume] ratio have been synthesized and applied reaching a considerable improvement of devices. As sensors work in oxygen atmosphere, the sensing mechanisms have been carefully studied for micro- and nanocrystalline SnO2. At first, sensors were built with thick films, afterwards, with thin films. The aim of this work was to build a very thin film sensor with nanocrystalline pure SnO2 in layers to optimize the device behavior to detect hydrogen ppm in air. The nanocrystalline pure SnO2 has been synthesized by three thin film techniques to compare results. Nanomateriales were characterized by DRX: crystallite size was measured by Scherrer equation and lattice stresses as produced by the different synthesis methods, were also studied by X-rays; absorption BET techniques and morphology studies were performed with SEM and HRTEM. Besides, the double meander electronic circuit (built by MEMS) to control sensors (already patented by the authors) was also improved by a new controlled, modular and portable circuit, being able to program the working temperature, the sensing operation modes, the heating and the commutation time between them.