The invention provides a preparation method of a Al<3+> doped
hexagonal phase NaYF4:Yb, Er upconversion material. The preparation method has the advantages that small-
radius Al<3+> is introduced intoa NaYF4:Yb, Er
crystal lattice through a trifluoroacetate high-temperature
thermal decomposition method to allow NaYF4 to have evident lattice
distortion, the ability of NaYF4 converting from alpha phase (cubic phase) to
beta phase (
hexagonal phase) is increased, and accordingly the purity of the
hexagonal phase NaYF4 upconversion material is increased, and the upconversion
fluorescence intensityof the hexagonal phase NaYF4 upconversion material is increased; in addition, the
doping of the Al<3+> can favorably lower the symmetry of the local
crystal field of activating agent Er<3+>, f-f forbidden transition can be destroyed to increase the probability of
radiative transition, reaction time can be shortened, and accordingly the small-size hexagonal phase NaYF4:Yb, Er upconversion materialcan be synthesized favorably, the upconversion
fluorescence intensity of the NaYF4:Yb, Er upconversion material is further enhanced, and the actual application of the NaYF4:Yb, Er upconversion material in the field of biomarkers.