The Up-conversion Luminescence And Its Temperature Characteristic Of Rare Earth Doped CaWO₄Phosphor

With the increasing progress of science and technology in recent years, rare earth dopedluminescence materials have potential applications in biomedicine, electric power industry,scientific research, and military defense and especially optical temperature sensor offluorescence. Intensity ratio based on rare earth doped luminescence materials and it becamea hot research both in our country and abroad. For the experiment measure the relationshipbetween the fluorescence intensity ratio and temperature of the two thermal coupling energylevels. It avoids the influence of the pump light source and optical signal transmission loss inthe process of experiment. The fluorescence intensity of rare earth radiation is not onlyrelated to the temperature, but also the choice of the host material. It has huge differences forthe fluorescence intensity with different host material. For example，, It has lower phononenergy when the host material be chosen as CaWO4, at the same time, the physical andchemical stability will be enhanced which make it to be a great potential application. In thispaper, CaWO4phosphor is taken as matrix material, CaWO4: Yb3+/Ho3+and CaWO4:Yb3+/Tm3+were made by high temperature solid phase method. The X-ray diffractionanalysis showed that the crystal structure of the sample keep good CaWO4lattice structure.In this article, fluorescence emission spectrum excited by different pump power which wereused to analyze the luminescence mechanism of rare earth ions, and much work were studiedon optical temperature system of Ho3+and Tm3+.The near infrared laser induced Up-conversion luminescence from Ho3+ions and itstemperature characteristic also have been studied. The Ho3+/Yb3+codoped CaWO4has beenprepared. Excited by a980nm diode laser, the two characteristics fluorescence belt of Ho3+have been successfully obtained. The UC process of Ho3+ions has been analyzied through thepower curve which are two photon processes. Stark splits of5F5energy level of Ho3+wereobserved in CaWO4. Meanwhile, according to the fluorescence intensity ratio method,temperature property of this split was studied between303K and723K.The near infrared laser induced Up-conversion luminescence from Tm3+ions and itstemperature characteristic have been studied. The Yb3+/Tm3+codoped CaWO4have been prepared. Excited by a980nm laser, up-conversion emissions centered at477nm(1G4→3H6),649nm(1G4→3H4),689nm(3F2→3H6) and689nm(3F3→3H6) in Tm3+,Yb3+codopedpolycrystalline CaWO4were successfully obtained. Based on the variation of emissionintensities with the pumping powers, the UC mechanism of Tm3+has been discussed.Meanwhile, temperature property of red up-conversion fluorescence was studied between313K and773K.