High-power infrared lasers are the heart of modern equipment in telecommunications, tracking and navigation systems, etc. The increasing power of lasers places high demands on the materials used as active laser media, which must exhibit high thermal stability and luminescence efficiency. Rare earth-doped yttrium titanium oxides, with the general formula (RExY1-x)2Ti2O7, represent a perspective class of materials for their phenomenal optical properties. Because the optical properties are highly sensitive to the structure and uniformity of the nanocrystals constituting the material, the knowledge of crystallization kinetics is necessary to prepare the nanocrystalline materials with tailored properties. We present a versatile sol-gel approach to nanocrystalline Y2Ti2O7 and (Er0,05Y0,95)2Ti2O7. We studied the nucleation process and crystallization mechanism of Y2Ti2O7 and (Er0.05Y0.95)2Ti2O7 from the amorphous xerogels. The crystallization temperatures of Y2Ti2O7 and (Er0,05Y0,95)2Ti2O7 were 792.5 ± 0.9 and 789.9 ± 0.5 °C, respectively. Based on calculated Avrami parameters the formation of Y2Ti2O7 from amorphous xerogel was driven by homogenous site-saturated nucleation. The introduction of Er3+ ions into host lattice of Y2Ti2O7 changed the crystallization kinetics causing the formation of (Er0.05Y0.95)2Ti2O7 occurred in a manner of homogenous nucleation with a constant nucleation rate. The different crystallization kinetics caused the nanocrystals of (Er0.05Y0.95)2Ti2O7 to be larger and exhibited broader nanocrystals size distribution than the nanocrystals of undoped Y2Ti2O7. The results provide fundamental information about nucleation and growth properties and crystal structure of investigated luminophores and give necessary information for preparing nanocrystalline powders with tailored properties for high-power photonic devices.Keywords: Nucleation, crystallization, pyrochlore, phosphors, (Er0.05Y0.95)2Ti2O7
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