The phase transformation behaviors of Sn2+-doped Titania gels

The transformation behaviors of Sn2+-doped titania gels, such as transformation temperature, conversion rate and the crystal granularity, were studied by using thermo-gravimetric/differential thermal analysis and X-ray diffraction methods. Experimental results show that, anatase, rutile and SnO2 phases can exist in the sintering products by varying Sn2+ content and sintering temperature. Sn2+-doping greatly depresses the growth of anatase and rutile crystals and so obtaining nanosized crystals The transformation temperatures of gel to anatase and anatase to rutile first decrease and then increase with an increase of Sn2+ content, while both of the transformation rates are associated with Sn2+ content, change in its valence and the sintering temperature. It is suggested that by adjusting Ti4+/Sn4+ ratio and sintering temperature, the crystal granularity and the ratio of anatase to rutile can be tailored to optimize properties of TiO2–SnO2 humidity sensing ceramics.