Research On The Synthesis And Luminescent Properties Of Aluminate And Gallate Phosphors

In this dissertation,with the help of Chemical Shift Model?CSM?,the impurity levels of transition metal ions with different valence states in semiconductors and wide band gap compounds were summarized and investigated from the viewpoint of vacuum referred binding energy.In order to further understand the theory,we investigated the luminescent properties of aluminate-gallate based luminescence materials,the luminescence mechanism and the energy level of the impurity ions were studied as well.The main contents are as follows:Firstly,the doping energy levels of transition metal ions?Cr,Mn,Fe?with different valence states in a variety of compounds were studied and the corresponding donor and acceptor energy levels in the band gap were summarized.For the wide band gap compounds,the charge transfer energies of the doped ions were collected and reviewed from literatures.With the help of Chemical Shift Model,the vacuum referred binding energy of 3d electrons were obtained.The results indicated that with the increase of the valence state for the same ion,the value of binding energy has a downward trend.Furthermore,the location of the bottom of conduction band has an important influence on the binding energy of doped impurities.The difference between these two energy levels may be caused by the Franck-Condon effect.Secondly,according to the Eu³⁺ charge transfer energy,the change of energy band structure when Ga³⁺ substituted Al³⁺ ions in CaAl₂O₄-CaGa₂O₄ system was investigated.The doping levels of different doped ions in this system were also studied.CaAlGaO₄ host was prepared with the high temperature solid-state reaction method at 1350? for 6h in air.A series of luminescence samples doped transition metal and lanthanides ions such as Eu³⁺,Tb³⁺,Dy³⁺,Sm³⁺,Ce³⁺ were prepared.CaAlGaO₄:Eu³⁺ samples give out red emission light due to the 5D0?7F2 transition of Eu³⁺ ions.CaAlGaO₄:Tb³⁺ phosphor has a strong green emission at 542 nm.With the cooperation of blue LED chip,Eu³⁺ and Tb³⁺ co-doped samples finally achieve white light.The emission of CaAlGaO₄: Dy³⁺ sample was mainly in the yellow-orange and blue light band.In addition,Sm³⁺ doped samples also have a strong orange light,when it co-doped with Eu³⁺ ions,the prepared samples have a wide range of orange-red emission.The color coordinations of all samples were displayed through the CIE chromaticity diagram.Finally,transition metal and lanthanides ions doped gallate based luminescence samples MGa₂O₄?M=Mg,Ba,Zn?were prepared by the solid-state reaction method,the photoluminescent properties of these doped ions were discussed.The emission spetrum of Cr³⁺ ions in MgGa₂O₄ host is mainly at 650nm-750 nm due to the 2E?2G??4A2?4F?transition of Cr³⁺ ions.Two kinds of raw materials MnO2 and MnCO3 were used in the experiment,and the raw materials were heated in air atmosphere.The results indicated that Mn ions mainly showed +2 valence state and occupied Mg²⁺ tetrahedral sites.Furthermore,the green afterglow phenomena of Mg0.98Ga₂O₄:0.02Mn²⁺ sample was observed and it last about 12 min.In addition,the variation of EV value for MGa₂O₄?M=Mg,Ba,Zn?was investigated and discussed.