Various Analyses of Phase Transformation from Titania Gel to Anatase Crystals

The phase transformation of titania gel to anatase crystals was characterized using a high-resolution transmission electron microscopy, differential scanning calorimetry and X-ray diffractometer. It was found that the transformation behavior was determined to be inconsistent using the three measurement techniques. The transmission electron microscopic results indicated that a small amount of anatase crystals existed in the amorphous gel that was dried at 100 °C for 24 h; however, the crystals were not detected by the differential scanning calorimetry and X-ray diffraction methods. As the sintering temperature increased, the lattice constant c of tetragonal anatase crystals gradually decreased and then stabilized with the standard constant (JCPDS card No 84-1285) at the temperatures above 300 °C. The lattice constant a remained relatively unchanged, which was in good agreement with the calculated results of the transmission electron microscopy and X-ray diffraction analyses. Moreover, the anatase crystal size determined by the transmission electron microscopy was larger than that by the X-ray diffraction analysis.