Investigation On NIR Upconversion And Long Persistent Emissions In Cr³⁺ Doped Gallogermanates

Recently reported gallium germanate based on ZnO has realized the up-conversion long afterglow luminescence of d state of Cr³⁺.Because the up-conversion luminescence of d state is difficult to realize,people pay more attention to gallium germanate.The analysis of ZnO doped gallium germanate system,Cd and Zn are in the same dominant family,the Cd molecular weight is greater than Zn,Therefore,the phonon energy of Cd is low and the symmetry reduction.This will benefit the up-conversion luminescence of f state and d state of rare earth ions and transition metals.In this thesis,ZnO and CdO are co-doped,and the following results are found in the new system:?1?We have prepared(Zn_xCd_1-x)₃Ga₂GeO₈:0.5%Er³⁺,5%Yb³⁺,1%Cr³⁺by using ZnO and CdO co-doped as substrates,and adjust the ratio of ZnO to CdO.Through experiments,we found that when ZnO is used as the substrate alone,the ceramic chip needs 400 degree heat treatment to see the upconversion luminescence of Cr³⁺,the upconversion of Cr³⁺ions can be clearly seen without 400 degree heat treatment after ZnO and CdO are co-doped.The luminescence intensity of rare earth ions and Cr³⁺increased several times,and the luminescence of the experimental product was the strongest when ZnO:CdO=3:2.?2?The upconversion of Cr³⁺ions comes from the sensitization of rare earth ions.The up-conversion luminescence of Cr³⁺was successfully realized by the experiment of doped Er³⁺through energy transfer.The excited state energy levels of the Tm³⁺ion Ho³⁺ion may also have the energy transfer between the Cr³⁺ion and the excited state energy level.Our experiments have successfully verified this.Materials doped with Tm³⁺and Ho³⁺ions can also enhance the luminescence of rare earth ions and Cr³⁺ions simultaneously.For the substrate doped with Tm³⁺,the luminescence of the experimental product is strongest when ZnO:CdO=2:1;for the substrate doped with Ho³⁺,the luminescence of the experimental product is strongest when ZnO:CdO=3:2.?3?The co-doping of ZnO and CdO not only enhances the upconversion luminescence of the f state and d state of rare earth ions and Cr³⁺ions,but also the afterglow is stronger than that of the single doped system.When ZnO:CdO=2:1,the afterglow is strongest,and this property occurs simultaneously in Er³⁺,Tm³⁺and Ho³⁺systems.