Lanthanide dopant-induced phase transition and luminescent enhancement of EuF3nanocrystals

Abstract

A novel strategy is proposed to prepare hexagonal EuF₃ nanocrystals by doping lanthanide ions (Ln³⁺) with large ionic radius (such as La³⁺, Ce³⁺, Pr³⁺, Nd³⁺ and Sm³⁺). Complete phase transition from orthorhombic to hexagonal phase can be achieved with the increase of ionic radius or doping concentration of Ln³⁺ ions. Meanwhile, the size and self-assembly degree of the product can be reduced dramatically. The possible growth and phase transformation mechanism of EuF₃ nanocrystals was proposed. Finally, Eu³⁺ ion was used as the structural probe to investigate the effect of phase transition on the luminescence. It was found that the emissions of the ⁵D₀ level of Eu³⁺ are greatly enhanced with the phase transition from orthorhombic to hexagonal phase. The luminescent enhancement is attributed to the larger radiative transition rate of the ⁵D₀ level in the environment with lower symmetry, which can be confirmed by Judd–Ofelt (J–O) theory.