Influence of the X-ray diffraction line profile analysis method on the structural and microstructural parameters determination of sol-gel TiO_2 powders

摘要

Four sol-gel TiO_2 powders have been prepared from titanium tetraisopropoxide. The calcined powders are then characterized by X-ray diffraction. Cell parameters are extracted using two Rietveld refinement programs (fullprof and maud) leading to close values and indicating a contraction of the a (or b) cell parameter and an expansion of the c cell parameter of the anatase phase with temperature. Crystallite size and microstrain are highly dependent not only on the sol synthesis but also on the diffraction line profile analysis (LPA) models (i.e., Williamson-Hall, Thomson-Cox-Hastings, Dehlez et al, and log-normal size distribution) employed. Discrepancies are then observed for the phase transformation critical size, the activation energy of grain growth, and the microstrain stored potential energy according to the LPA approach used to calculate the microstructural parameters.