Quantitative Analysis of Amorphous Contents in Photocatalytic Titania Powders

Abstract

Titania powders with different crystallinity were prepared from alkoxide-derived amorphous titania powders by heat-treatments at temperatures of less than 600°C. The amorphous and anatase contents of titania powders were analyzed by measuring the heat of crystallization in DSC and by X-ray diffraction measurements with the Rietveld method. Amorphous powders showed an exothermic peak due to the crystallization of amorphous to anatase at around 360°C in DSC. The heat of crystallization was 163 J/g. The amorphous contents of titania powders decreased with an increase of the heat-treatment temperature. On the other hand, the amorphous powder began to crystallize under a heat treatment at 300°C in the XRD profile. The intensity of diffraction lines attributed to anatase became stronger with an increase of the heat-treatment temperature. The amorphous contents of titania powders decreased with the heat-treatment temperature in an analysis of the Rietveld method. There are linear relationships between the amorphous contents and the temperature in both results from DSC and the Rietveld methods. We examined the relationship between the crystallinity of the tiatnia powders and their photocatalytic activity. The photocatalytic performances of titania powders were evaluated upon the removal of acetaldehyde. The results showed that the photocatalytic activity of titania powders increased with an increase of the anatase contents.