Gas Sensors Built with Nanomaterials and Provided with a Heating Double Purpose Hot-plate

Abstract

Pure or doped SnO2, has been used to build resistive type gas sensors from several decades. This subject has been retaken using pure or doped nanocrystalline SnO2 to build the sensors, finding considerable advantages in devices performance. The sensors working temperature (Tw) decreases from (350-450) 0C to (180-200) 0C in comparison with that of devices built with microcrystalline conventional material. Sensitivity of sensors built with nanocrystalline material in comparison with that of devices built with conventional microcrystalline material, increases from 30 % to 37 %. In this work, SnO2 is synthesized using two different modified techniques based on gel-combustion and reactive oxidation and results of both syntheses are compared. Nanomaterials are characterised with X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Field Emission Electron Scanning Microscopy (FESEM) and absorption techniques (BET). An electronic system, already patented by the authors, enables to alternatively measure the sensor resistivity (which is proportional to the adsorbed gas concentration) and set a constant working temperature, thus contributing to considerably save energy.