Synthesis,Properties And Anti-Counterfeiting Application Of Several Rare Earth Luminescent Materials

Rare earth luminescence materials play an important role in recent science and technology,which have been widely used in lighting,display,anti-counterfeiting and other fields.In recent years,people have proposed higher demand for anti-counterfeiting technology,and higher requirements for high-quality anti-counterfeiting.Therefore,developing novel luminescent materials with excellent performance has high practical significance.Here,using Na Ba Sc₂（PO₄）₃,Gd₃Ga O₆,and Gd Ga₂Al（BO₃）₄ as hosts,a series of novel luminescent materials were designed and synthesized by doping rare earth and other ions as activators.Their crystal structure,luminescent properties,and relative applications were studied,and the following meaningful results were obtained:1、A series of novel langbeinite-type phosphate Na Ba Sc₂（PO₄）₃:Eu²⁺/Ce³⁺/Tb³⁺and Na Ba Sc₂（PO₄）₃:Yb³⁺-Er³⁺/Ho³⁺/Tm³⁺phosphors were designed and synthesized.With doping the Eu²⁺ions,the samples emit blue light with a peak at 434 nm;and with doping the Ce³⁺ions,near-ultraviolet light with a peak at 370 nm is emitted.For Na Ba Sc₂（PO₄）₃:Eu²⁺/Ce³⁺-Tb³⁺co-doped samples,the energy transfer processes between Eu²⁺-Tb³⁺and Ce³⁺-Tb³⁺is founded,and involve quadrupole-quadrupole and dipole-dipole interactions,respectively.The adjustable emission color from blue to yellow of Na Ba Sc₂（PO₄）₃:Eu²⁺,Tb³⁺can be realized by regulating the concentration of Eu²⁺and Tb³⁺,and a White LED with ideal properties was manufactured.In addition,the prepared Na Ba Sc₂（PO₄）₃:Yb³⁺-Er³⁺/Ho³⁺/Tm³⁺samples can exhibit characteristic yellow,blue,and red upconversion luminescence under the excitation of 980 nm near-infrared light.The emission intensity,ratio of emission color,and luminescence mechanism were investigated.By combining these two materials with up/down conversion luminescence,an anti-counterfeiting label was prepared,and satisfactory anti-counterfeiting effects were obtained.2、A series of Bi³⁺and Er³⁺doped Gd₃Ga O₆ phosphors were successfully prepared,and their luminescent properties were studied.In the materials doped with single Bi³⁺,the occupation of Bi³⁺ions include two different Gd³⁺sites,which form Bi（I）and Bi（II）luminescent centers,and exhibit blue violet light at 409 nm and orange light emission at 594 nm,respectively.This materials with Er³⁺single-doped can exhibit green down-shifting luminescence,green upconversion luminescence（under the excitation of 980 nm）,and yellow upconversion luminescence（under the excitation of1530 nm）.Based on this,an anti-counterfeiting device with more security levels has been designed and manufactured,and different luminescent patterns can be obtained under the excitation of 302nm,365 nm,980 nm,and 1530 nm.3、Gd Ga₂Al（BO₃）₄:Cr³⁺phosphors were synthesized and their crystal structure,luminescent properties and thermal stability were studied in detail.It is shown that the crystal structure of Gd Ga₂Al（BO₃）₄ can be indexed to the R32 space group of the trigonal system.The Cr³⁺ions occupy the Ga³⁺site,forming an octahedron coordinated with six oxygen atoms.The Gd Ga₂Al（BO₃）₄:Cr³⁺samples exhibit a broadband near-infrared emission of Cr³⁺ions:the excitation spectrum consist of two bands at 422 nm and 610 nm,and the emission spectrum covers a range of 650-850 nm.The temperature-dependent spectrum revealed that the luminescent intensity maintained at 66.7%of room temperature at 150℃,indicating that it has a preferable thermal stability.Combining the phosphor with commercial blue light chips,the near-infrared LED have been prepared.