The gas-sensing potential of nanocrystalline SnO2 produced by a mechanochemical milling via centrifugal action

Abstract.

In this work, the synthesis of undoped nanocrystalline tin dioxide powders and the subsequent preparation of SnO₂ thick-films were studied. An initial mixture of SnCl₂ and Ca(OH)₂ was sealed in a vial for milling in an air atmosphere. Heat treatment of the milled powder resulted in the formation of tetragonal and orthorhombic SnO₂ phases, which was confirmed by X-ray diffraction (XRD) analysis. It was found that crystallite size could be controlled by varying the milling time, the rotation speed and the temperature used for the heat treatment. Crystallite sizes in the range 20 to 30 nm (determined by XRD measurements) were obtained. The total pore volume was 0.22 ml/g for a measured particle size of 37 m²/g. No contamination of the powder during milling was found. The response of the prepared thick-films to H₂S gas in the concentration range 0.5 to 10 ppm in air was investigated as a function of the preparation conditions. The advantage of mechanochemical synthesis of powder is its relative simplicity, low cost and possibility of obtaining isolated, unagglomerated nanosized grains. It is shown that chemical reactions, which usually occur in the vibratory mill to produce the SnO phase, can also be initiated during a short processing time in the centrifugal mill.