Synthesis and characterization of metal-doped humidity sensors based on hematite for environmental monitoring applications
Afify, Ahmed S.
Humidity sensors have several applications in both industrial processing and environmental control. Pure and doped hematite have proved to exhibit a remarkable humidity sensing properties. The aim of this investigation is to study the effect of doping of some metal ions (Li+, Mg+2, Ba+2, Sr+2, and Na+) onto the crystalline hematite and to determine their sensitivity towards relative humidity (RH). The obtained crystalline samples were characterized by particle size distribution, X-Ray Diffraction (XRD) combined with Field Emission Scanning Electron Microscopy (FESEM). Sensors were screen printed onto an α- alumina substrates with platinum electrode followed by Screen printing of doped α-Fe2O3 powders and a binder for the appropriate rheological properties to the paste. After deposition samples were dried in air at room temperature prior to be heat treated at 800°C for 1h. Humidity sensors were tested in a laboratory apparatus made of a thermostated chamber, operated at 25°C, in which relative humidity (RH) could be varied between 0 and 96%. The doped sodium metal ions (Na+) hematite sample showed a significant response towards relative humidity at room temperature.