Radiative transition dynamics of holmium ions-doped LaF_3 nanocrystals

摘要

AbstractHo3+-doped LaF3nanocrystals with 1.0, 3.0, and 5.0 mol% Ho3+have been prepared by hydrothermal method. The nanocrystals possess hexagonal structure with$$Pstackrel{-}{3}c1$$P3-c1space group with lattice parametersa = 7.172 ± 0.002 Å andc = 7.342 ± 0.002 Å. The room temperature absorption, luminescence spectra of LaF3:Ho3+was investigated in detail. Judd–Ofelt theory has been applied to estimate$${{Omega }}_{{uplambda }}$$Ωλ(λ = 2, 4, 6) intensity parameters. For LaF3:5%Ho3+sample,$${varOmega }_{2}=1.872times {10}^{-20}{text{cm}}^{2},$$Ω2=1.872×10-20cm2,$${varOmega }_{4}=4.006times {10}^{-20}{text{cm}}^{2}$$Ω4=4.006×10-20cm2and$${varOmega }_{6}=4.720times {10}^{-20}{text{cm}}^{2}.$$Ω6=4.720×10-20cm2.Based on these Judd–Ofelt parameters, various radiative parameters such as radiative transition probabilities$${ A}_{R},$$AR,radiative lifetime$${ tau }_{R},$$τR,branching ratios$${beta }_{R}$$βRand stimulated emission cross-section$${sigma }_{em}left({lambda }_{p}right)$$σemλpfor various emission levels of LaF3:5%Ho3+sample have been determined. It is found that the luminescence quantum efficiency of5F5excited state is decreased from 55.8 to 37.9% with increasing Ho3+concentration from 1 to 5 mol%.