Preparation And Optical Properties Of Trivalent Bismuth Ion-doped Gallate Phosphors

As the growth of global population and the continuous improvement of the degree of industrialization,there is a contradiction between the increasing demand for energy and the reduction of fossil fuel storage.Therefore,it is becoming increasingly important to develop new energy-saving and environmental protection materials to solve this problem.The pc-WLED light-emitting diode technology,which has been widely used in the field of lighting,has great potential in reducing world energy consumption because of its low cost,easy packaging,high efficiency and environmental protection.It is well-known that Bi³⁺ion has the characteristic absorption in the ultraviolet region basically and almost no absorption in the visible region,which can effectively avoid the problem of reabsorption.Particularly the S-P transition of Bi³⁺ion is beneficial to achieve efficient emission,and the emission of Bi³⁺ion is greatly affected by the change of the surrounding crystal field environment,leading to the well control of different band emission in a large spectrum range.On this basis,we manipulate the defect states to systematically study and control the luminescence properties of Bi³⁺ion.The purpose of our work is to solve the problems of high color temperature,poor thermal stability and low efficiency for current Bi³⁺ion activated phosphors in practical applications.In this paper,gallium is selected as the matrix,because it is much easier for Bi³⁺ion to be activated in gallium matrix by doping.The gallium matrix has a special ring crystal structure containing Ga O₄ tetrahedron,when sintering in the high temperature,the Bi³⁺-doped gallium matrix is easier to produce defects and shows excellent optical properties.The corresponding research results are as follows:(1)A novel Sr Ca Ga₄O₈:Bi³⁺blue phosphor was designed and synthesized.The internal quantum efficiency(IQE)of the phosphor was 92.8%at 330 nm and 90%at 365 nm.pc-WLED devices were fabricated by using SCG:0.06Bi³⁺,commercial green phosphor Ba₃Si₆O₁₂N₂:Eu²⁺,red phosphor Ca Al Si N₃:Eu²⁺and 365 nm UV chips.The CRI of pc-WLED devices was 82 at 3.2 V supply voltage and 50 m A current.However,during the study of its thermal stability,we found the emission intensity of Sr Ca Ga₄O₈:Bi³⁺Phosphor remains about only 50%of the initial intensity at 150?,meaning that the thermal stability still needs to be strengthened;(2)A novel anti thermal quenched Ba Ca Ga₄O₈:Bi³⁺yellow green phosphor was designed and synthesized by trap compensation strategy.The emission intensity can reach119.24%of the initial intensity at 300?.A series of Ba_xCa_yGa₄O₈:0.015Bi³⁺(x=0.94-1.08,y=1.06-0.92)phosphors have been developed to achieve high thermal stability single-phase white light emitting phosphors.Under 365 nm UV excitation,the emission intensity can still reach 76.42%of the initial intensity at 150?,with excellent color stability;(3)A novel bright orange emitting Ba Sr Ga₄O₈:Bi³⁺,K⁺gallinate phosphor with low dimensional chain structure is reported.Based on the oxygen vacancy induced Bi³⁺activation strategy,the effective Bi³⁺activated long wavelength emission was realized.We further used K⁺ion to produce more oxygen vacancy defects in the matrix,resulting in increase of emission intensity more than 5 times than before.We show that the orange emission comes from the energy splitting of Bi³⁺ions through oxygen vacancies.pc-WLED devices were fabricated by mixing commercial blue phosphor BAM:Eu²⁺,green phosphor Ba₃Si₆O₁₂N₂:Eu²⁺with 365 nm UV chip.The CRI of the device is 87.7and the internal quantum efficiency is 65.5%under the condition of power supply voltage of 3.2 V and current of 50 m A.BSG:Bi³⁺,K⁺with high CRI and high quantum efficiency have great potential as novel long wavelength phosphors for NUV excited full spectrum pc-WLED lighting.