Preparation And Luminescence Properties Of Rare Earth Ions Eu, Tb Doped The Unitary Or Binary System Of CaMoO₄ And SiO₂ Materials

In this paper, first of all, the sample CaMoO₄:RE(RE= Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺) has been prepared with the coprecipitation method and high-temperature roasting method. TG-DTA spectra shows that the energy of the samples is up to the maximum implying that it has formed stable structures at 800℃(CaMoO₄:Eu³⁺),850℃(CaMoO₄:Tb³⁺) and 866℃(CaMoO₄:Eu³⁺:Tb³⁺) respectively. XRD pattern of the sample shows that the CaMoO₄:Eu³⁺ (800℃),CaMoO₄:Tb³⁺ (850℃)and CaMoO₄:Eu³⁺:Tb³⁺ (866℃), at the single phase, is a representative scheelite structure of CaMoO₄.Due to three Ca²⁺ replaced by two RE in the cell of the samples CaMoO₄:RE(RE= Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺), the crystal produced tiny crystal defect, so that it has the samples CaMoO₄:RE (RE=Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺) form the semiconductor which is possessed of p-n junctions, as the samples are waken, the hole and the electron around the hole, it can form a F- (Frenkel) exciton, which is at the bound state, in the crystal.The three-dimensional fluorescence spectra, excitation and emission spectras of the samples are investigated and reveal that the defect structures of the sample not only enable the but also make energy of MoO₄^2- high efficiently transfer RE, especially the 4f electron of the RE transit, with the 488 nm of MoO₄^2- partly or completely overlapped, is greatly strengthened. For the sample CaMoO₄:Eu³⁺, as a result, the emission spectra withλex=465nm shows the emission intensity of the spontaneously activated fluorescence MoO₄^2- is greatly weaken or even quenching, while the red light luminescence intensity of the 5D0-7F2 transition(612nm)of Eu³⁺ is greatly enhanced, similarly the emission spectra of CaMoO₄:Tb³⁺ withλex=488nm shows the emission intensity of the green light luminescence intensity of the ⁵D₄→⁷F₅ transition (544nm)of the Tb³⁺ is greatly enhanced. About the emission spectra of the sample CaMoO₄:Eu³⁺:Tb³⁺ withλex=302nm, it can emit blue,green and red light at the same time. These particular advantages tell us a fact that the samples CaMoO₄:RE(RE= Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺) will become the luminescence material that is of great potentially used value.In addition, the sample RE(RE=Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺) to CaMoO₄ and SiO₂ matrix light-emitting materials, it are prepared by the sol-gel method. XRD spectra of the sample show that the samples are mainly formed by the structure of amorphous SiO₂, but the small crystals of CaMoO₄:RE (RE=Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺),which are in SiO₂ network structure , and in a small crystal the defective internal still have caused RE to replace Ca²⁺, thus as a result of generating p-n junction and F-(Frenkel) exciton. Through three-dimensional fluorescence spectra, excitation and emission spectra of the sample showed that: CaMoO₄:RE(RE=Eu³⁺, Tb³⁺ or co-doped Eu³⁺ and Tb³⁺) still has all the character of a small crystal,but after all in SiO₂ network structure, it make transfer part of the energy from MoO₄^2- to the RE (RE=Eu³⁺ , Tb³⁺ or co-doped Eu³⁺ and Tb³⁺), the other part of energy is saved for its own emitting phosphor of MoO₄^2-. Such as the emission spectrum of the sample SiO₂:CaMoO₄:Eu³⁺ atλex= 465nm, it takes on green light of MoO₄^2-in 498nm and 514nm and red light of Eu³⁺ in 612nm; the emission spectrum of SiO₂:CaMoO₄:Tb³⁺ inλex= 488nm, it presents two green light of MoO₄^2- in the 517nm and Tb³⁺ in the 544nm; the emission spectra of sample materials for SiO₂:CaMoO₄:Eu³⁺:Tb³⁺inλex= 302nm, it emits blue, green and red light at the same time, and the intensity is basically the same of three colors. Therefore, it can take on one, two or three colors of light in the same material SiO₂:CaMoO₄:RE(RE=Eu³⁺, Tb³⁺ or co-doped Eu³⁺and Tb³⁺).