Enhancement of structure stability and luminescence intensity of LiYF4:Ln3+ nanocrystals

Abstract

LiYF4 nanocrystals with tetragonal structure were adopted as the host materials for the phosphors and scintillators owing to the low phonon energy and high optical transparency. LiYF4:Ln3+(Ce3+,Eu3+) nanocrystals were fabricated by solvothermal method. Under UV excitation, they could emit visible light. In order to improve the luminescence intensity, the method of co-doping LiYF4 nanocrystals with Sc was adopted. Sc3+ ions could reduce the lattice expansion caused by the doping of Ce3+ or Eu3+ whose ionic radius was larger than Y3+. Crystal structure of Li(Y,Sc)F4:Ln3+ kept much more stable and the luminescence intensity could be significantly enhanced when the concentration of Sc was a moderate value. Thermoluminescence was employed to analyze the electron traps in Li(Y,Sc)F4:Ce3+. Results suggested that the suppression of the generation of electron traps with the co-doping of Sc contributed to the enhancement of luminescence intensity of LiYF4:Ce3+.