Preparation and scintillating properties of sol-gel Eu ³⁺, Tb ³⁺, co-doped Lu ₂O ₃ nanopowders

Nanocrystalline Eu ³⁺, Tb ³⁺ co-doped Lu ₂O ₃ powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA) and infrared spectroscopy (IR) were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O2 atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD) to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu ₂O ₃ nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM) study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu ³⁺ dopant (5 mol%), Tb ³⁺ codoped Lu ₂O ₃ exhibited a typical red emission at 611 nm (D _o→ ⁷F ₂), furthermore, the effect of Tb ³⁺ molar content (0.01, 0.015 and 0.02% mol) on the Eu ³⁺ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb ³⁺ content.