Structure transition of nano-titania during calcination

In order to study the structure transition during calcination, nano-titania powders prepared by hydrolyzing precipitation approach and calcined at 300, 400, 500, 600 and 700 degreesC were characterized by XRD, TEM and electron diffraction(ED), respectively. The results show that titania powders calcined below 500 degreesC are almost composed of anatase, rutile appears below 500 degreesC and its ratio increases gradually with increase of calcin temperature; nano-titania particles are smaller than 40 nm mostly and the dispersion is related to calcining temperature; the inter-planar distances of nano-anatase single crystalline change gradually when calcing temperature increases to 500 degreesC; so do that of nano-rutile single crystalline when calcining temperature charges from 600 to 700 degreesC. The conclusions can be drawn that the temperature of transformation from anatase to rutile is below 500 degreesC and the process carries on gradually. Both inter-planar distances and the structure of nano-titania transform gradually with increasing calcing temperature.