Controllable Synthesis And Luminescence Properties Of Rare Earth Doped Borate Phosphors

The special 4f electrons configuration of lanthanides and the BO33-group with the stable regular triangle based on the sp2 hybridization,make the luminescent materials of rare earth doped borate have excellent optical properties and chemical stability.In this thesis,a series of Re3+-doped borate phosphors were successfully prepared by the oleic acid(OA)-assisted hydrothermal method.The effects of the synthesis parameters and conditions on the structures and shapes of the prepared materials,the possible crystalline growth mechanism and luminescence properties of YBO3:Eu3+ phosphors were investigated in details.The main results obtained are described as follows.Uniform ReBO3(Re = Y,Dy,Ho,Er and Yb)spherical microstructures with the diameter of about 20 ?m were successfully prepared by the oleic acid(OA)-assisted hydrothermal method.The results showed that,the radius of Re3+,the solvent amount,synthesis temperature,pH value in synthesis solution,OA amount,molar ratio of Y3+/BO33-have an obvious influence on the structure and morphology of samples.Based on the above results obtained,the possible formation mechanism of YBO3 crystals was proposed.YBO3:3-5%Eu3+ samples prepared by the OA-assisted method displays bright white color under excitation of 394 nm and the chromaticity coordinate were(0.33,0.32)and(0.34,0.33),respectively,which was much close to the standard white point,and the quantum yield of the YBO3:5%Eu3+ sample can reach to 44.59%.However,YBO3:5%Eu3+ shows the orange-red emission and the quantum yield can reach to 79.73%when the excitation wavelength is 270 nm.And the light color of YBO3:Eu3+ can be varied with the concentration of Eu3+ and the excitation wavelength.And the morphology of YBO3:5%Eu3+would also affect its luminescence intensity(LI),and LI of the sample with 3D hexagonal micro structure was the strongest and that with porous sphere was weakest.YBO3:xEu3+/Tb3+ samples prepared have nice crystal form and uniform morphology with the diameter of about 20 ?m.When the mole ratio of Eu3+/Tb3+ was 1/5,it can emit close-white color under excitation of 235 nm,in which the chromaticity coordinate was(0.30,0.30).The pure hexagonal phase YBO3 samples were synthesized with different boron or yttrium raw materials,and the molar ratio of B/Y and pH values would affect the structure and morphology of samples.At 180 ? and pH value 7 of synthesis solution,using Y(NO3)3 and C12H27BO3 raw materials and Y/B of 2/4,the YBO3 spheres could be prepared;using Y(NO3)3 and Na2B4O7·1OH2O raw materials and Y/B of 2/6,the YBO3 porous spheres could be prepared;using YCL3·6H2O and H3BO3 raw materials and Y/B of 2/8,the tyre-like YBO3 spheres was prepared.And the quenching concentration of Eu3+ for the above three kind of YBO3:Eu3+ materials was 7%(C1),7%(C2)and 9%(C3)respectively.Among above three luminescent materials,the luminescence intensities are ranked in the order of C2>C3>C1.