Crystallization properties of RE-doped (RE = Eu, Er, Tm) Zn2TiO4 prepared by the sol-gel method
Résumé
Samples of pure and rare earth (RE)-doped nanocrystalline Zn2TiO4 (RE = Eu, Er, Tm) have successfully been prepared by the single batch sol-gel method in a form of powders. The powders were annealed up to 1200 °C and analyzed by DTA and XRD methods. Sizes of formed nanocrystals were calculated from the Scherer equation and verified by the SEM analysis. Activation energies of crystallization were calculated using the Kissinger, Ozawa and Augis-Bennett approximations and reaction mechanisms were proposed evaluating the Avrami exponents from the Johnson-Mehl-Avrami equation. It has been found that RE elements particularly substitute zinc ions in the crystal lattice and are fully soluble up to 0.5 at.% related to the some of cations. Furthermore, the results have shown that the presence of RE elements blocks the crystallite growth and supports the nucleation process leading to the formation of smaller and more uniform nanocrystals compared to the undoped Zn2TiO4.