Surface modified tin oxide pellets for CO gas sensing

Tin oxide (SnO₂) powders were obtained by the homogeneous precipitation method by using urea as precipitation agent. The SnO₂ powders were later ball milled for using a homemade stainless steel die and pressed with a pressing machine to manufacture thin pellets. After several experimental trials, stable SnO₂ pellets were formed by manual pressing. Copper (Cu) modified SnO₂ pellets (Cu-SnO₂) were prepared by impregnation method. Manufactured pellets were surface modified from two different aqueous 1 wt% Cu solutions. The metallic copper residues were removed from a further heat treatment. Structural analysis was performed by X-Ray diffraction (XRD) to confirm the SnO₂ rutile phase. The morphological and compositional characteristics of the pellets were analyzed by Scanning Electron Microscopy (SEM) and Energy dispersive spectrometry (EDAX) techniques, respectively. Later, silver contacts were deposited on the pellets surface by the thermal evaporation technique. The sensing properties of these pellets were measured in carbon monoxide (CO) atmosphere at different operation temperatures. Metallic copper crystals and porous CuO bars were formed on the surface of the pellets, depending on the impregnated solutions. The sensing properties of the SnO₂ pellets were tested as a function of the gas concentration and measuring temperatures.