Preparation And Properties Of Several Doped Gallium Luminescent Materials

Rare earth/transition metal ions doped Ln₄Ga₂O₉（Ln=Gd,La,Y）,Sr₃Ga₂O₆,and Zn₃Ga₂Sn O₈luminescent materials were synthesized by a sol-gel method or hydrothermal method.The phase structures,morphologies,components and optical properties of the samples were investigated by X-ray powder diffraction,scanning electron microscope,energy dispersive spectrometer,ultraviolet-visible diffuse reflectance spectroscopy and fluorescence spectroscopy.The luminescent properties of those rare earth/transition metal ions doped luminescent materials were systematically studied.Through experimental research,the conclusions obtained are as follows:Dy³⁺doped Ln₄Ga₂O₉（Ln=Gd,La,Y）crystals with monoclinic structure were successfully prepared by a sol-gel method.The preparation conditions have a great influence on the phase structure and luminescence properties of the Dy³⁺doped Ln₄Ga₂O₉（Ln=Gd,La,Y）samples.When the p H is 7-8,the ratio of n（Ln+Dy）/n（Ga）is 2:1,and the calcination temperature is 700-800℃,the obtained samples display good luminescent properties.Dy³⁺doped Ln₄Ga₂O₉（Ln=Gd,La,Y）luminescent materials can emit the Dy³⁺yellow characteristic emission bands and blue characteristic emission bands under the excitation of ultraviolet light,which originate from the ⁴F_9/2→⁶H_15/2and ⁴F_9/2→⁶H_13/2of Dy³⁺,respectively.The luminescence intensity of Dy³⁺-doped Ln₄Ga₂O₉（Ln=Gd,La,Y）luminescent materials varies with the doping amount of Dy³⁺.The optimized doping amount of Dy³⁺is 0.5%,1%and 1%for Gd₄Ga₂O₉,La₄Ga₂O₉and Y₄Ga₂O₉samples,respectively,and excessive doping of Dy³⁺will lead to concentration quenching.According to the concentration quenching mechanism,it is concluded that the quenching mechanism of Dy³⁺doped Gd₄Ga₂O₉samples belongs to the electric dipole-electric dipole interaction mechanism.The possible luminescence mechanism of the samples were analyzed.In addition,the decay curve of the samples show that the amount of Dy³⁺doped in Ln₄Ga₂O₉（Ln=Gd,La,Y）matrix increases,which leads to the decrease of the distance between Dy³⁺ions,and the increase of the energy exchange rate,which makes the rate of energy exchange increase,and the fluorescence lifetime of the samples decreased with the increase of Dy³⁺doping.Tb³⁺doped Sr₃Ga₂O₆luminescent materials were synthesized by sol-gel method,and the effect of synthesis conditions on the phase structure and luminescent properties of the samples were systematically studied.The results show that the Sr₃Ga₂O₆:Tb³⁺luminescent material with cubic structure was synthesized at 900℃.The ultraviolet-visible diffuse reflection spectrum shows that the sample is a direct band gap semiconductor with an optical band gap of 5.13 e V.And the scanning electron microscope images show that its morphology is irregular.Tb³⁺-doped Sr₃Ga₂O₆luminescent material can be effectively excited by230 nm ultraviolet light,and emit the characteristic emission of Tb³⁺ions,which correspond to the characteristic transition emission bands of ⁵D₃→⁷F₆and ⁵D₄→⁷F_{J（J=6,5,4,3）},respectively,and the intensity of the emission peak for the ⁵D₄→⁷F₅transition is the strongest.The luminescence intensity and average decay time of the samples vary with the doping amount of Tb³⁺.When the doping amount of Tb³⁺is higher than 0.5%,the cross relaxation phenomenon will occur,which will reduce the luminescence intensity of the sample.With the increase of the doping amount of Tb³⁺,the average decay time decreases gradually,which verifies that the transition probability of energy transfer between Tb³⁺ions increases,it shows that the increase of Tb³⁺ion concentration promotes the energy transfer between of Tb³⁺ions.At the same time,the possible luminescence mechanism of the sample is also analyzes reasonably.Zn₃Ga₂Sn O₈:Cr³⁺phosphors were successfully synthesized by a hydrothermal method,and the effects of different n（Ga）/n（Sn）raw material ratios,calcination temperature and Cr³⁺doping amount on the phase structure and luminescent characteristics of the material were studied.The results show that different ratio of n（Ga）/n（Sn）raw materials have great influence on the structure of the obtained solid solution products.The structure of the prepared Zn_1+xGa_2-2xSn_xO₄solid solutions change with the increase of x.The matrix structure affects the electronic transition and energy transfer of doped ions,which makes the luminescent properties of the materials first increase and then decrease.The Zn₃Ga₂Sn O₈solid solution exhibits excellent luminescent properties.Different calcination temperature conditions affect the structure and luminescence properties of the materials.With the increase of calcination temperature,the luminescence intensity increases,and the optimal preparation temperature is 1100°C.The prepared samples can be effectively excited by 270 nm ultraviolet light,and a characteristic red emission peak belonging to Cr³⁺ions appear near 698 nm（²E→⁴A₂）;and the luminescence intensity first increases and then decreases with the increase of Cr³⁺doping concentration.When the doping amount of Cr³⁺exceeds 1%,the phenomenon of concentration quenching will appear.In addition,the results of the time decay curve confirm that with the increase of Cr³⁺doping concentration,the concentration of lattice defects in the prepared samples increases,resulting in more excited state particles being captured by defects,that is,the probability of fast non-radioactive transition increases,and the fluorescence lifetime gradually decreases.