Luminescence behavior of Eu³⁺ doped LaF₃ nanoparticles

Europium-doped LaF₃ nanoparticles have been prepared by the ionic reaction in the ethanol at 60 °C. From the XRD pattern of nanoparticles and the emission spectra of Eu³⁺ ions, it has been concluded that the Eu³⁺ ions could easily substitute the La³⁺ sites and the solid solution La_1-xEu_xF₃ can be synthesized. Due to very low phonon energies of LaF₃ matrix, the ⁵D₁ emission of Eu³⁺ ions in La_1-xEu_xF₃ nanoparticles can be observed at room temperature when doping concentration of Eu³⁺ ions is lower than 30 mol%. The quenching process of ⁵D₁ emission can be attributed to cross-relaxation. Since clusters of Eu³⁺ ions and resonance energy transfer only occurs within one particle due to the hindrance by the particle boundary, the concentration quenching resulted from resonance energy transfer between neighboring Eu³⁺ ions occurs at higher Eu³⁺ concentrations in the Eu³⁺ doped LaF₃ nanoparticles. © 2004 Elsevier B.V.