Energy transfer between UO₂ ²⁺ and Eu³⁺ in β-NaYF₄

β-NaYF₄:UO₂ ²⁺, β-NaYF₄:Eu³⁺ and β-NaYF₄:UO₂ ²⁺,Eu³⁺ have been prepared by hydrothermal synthesis. Emission spectra of these three samples were measured at temperatures down to 10 K. Eu³⁺ ions occupy several distinct sites with symmetry C₃ or lower in this host lattice whereas UO₂ ²⁺ ions form a disordered system with fourfold or fivefold equatorial fluoride coordination geometry. The occurrence of energy transfer from UO₂ ²⁺ to Eu³⁺ is demonstrated by excitation spectra and lifetime measurements. © 2008 Elsevier B.V. All rights reserved.