Preparation And Luminescence Properties Of Eu²⁺,Cr³⁺ Doped AlF₃ Phosphors

Luminescent materials play an important role in the rapid development of information today,with considerable scale and market demand.In addition to daily lighting,there are also a wide range of high-tech fields such as communications,biomolecular probes,aerospace,optical computers application.Fluoride system luminescent materials have the advantages of stable chemical properties,strong ionicity,high electronegativity,strong insulating properties,small refractive index,wide optically transparent area and so on.In this paper,AlF₃ is used as the host material,Eu²⁺and Cr³⁺are used as the doping ions,and two fluoride luminescent materials are synthesized by the high-temperature solid-phase method,the structure and fluorescent properties of the system are systematically studied.The specific work is as follows:Using AlF₃,EuF₂,NH₄F,Cr（NO₃）₃·9H₂O as raw materials,AlF₃:Eu²⁺near ultraviolet phosphor and AlF₃:Cr³⁺red phosphor were synthesized under high temperature solid phase method at 960℃.Analyze and characterize the sample image by XRD diffractometer,analyze and study the excitation spectrum,emission spectrum and fluorescence lifetime of the prepared sample by PL fluorescence spectrometer,and carry out the color coordinate of the prepared sample by CIE1931 colorimetric coordinate software.Describe and analyze the factors of rare earth doped ion concentration and holding time.The AlF₃:Eu²⁺phosphor was synthesized at a high temperature of 960℃,and the X-ray diffraction pattern of the prepared sample completely matched the diffraction peak of the standard card（PDF#044-0231）.For the prepared AlF₃:Eu²⁺phosphor,when the emission wavelength is 360nm,the excitation peak of the sample is in the range of230nm to 260nm,and the strongest peak is in the vicinity of 250nm.When the 250nm wavelength light is used as the monitoring light,the emission spectrum of AlF₃:Eu²⁺has a sharp peak at 360nm,which belongs to Eu²⁺4f⁷(⁶P_7/2)→4f⁷(⁸S_7/2)energy transition absorption.The CIE chromaticity coordinate of the phosphor is（0.1737,0.0049）.This point is located in the near ultraviolet region on the color coordinate diagram.When the heat preservation time is 3h,the excitation and emission intensity is the highest,which is the best heat preservation time.The fluorescence lifetime curves of AlF₃:Eu²⁺phosphor under different Eu²⁺doping concentrations under 250nm ultraviolet excitation were studied,and it was observed that with the increase of Eu²⁺ion concentration,the fluorescence lifetime was shortened.The AlF₃:Cr³⁺phosphor was synthesized at a high temperature of 960℃,and the X-ray diffraction pattern of the prepared sample completely matched the diffraction peak of the standard card（PDF#044-0231）.The prepared AlF₃:Cr³⁺phosphor has two broad excitation bands at 380⁴50 and 500⁶00nm when the emission wavelength is695nm.The excitation band of 500⁶00 nm is attributed to the transition of ⁴A_2g（F）→⁴T_2g（F）of Cr³⁺,and its center wavelength is at 560nm.The excitation at 380⁴50 nm is due to the transition of ⁴A_2g（F）→⁴T_1g（F）of Cr³⁺,and its central wavelength is at407nm.At the excitation wavelengths of 407nm and 560nm,the samples can be observed to have a sharp emission peak at 695nm,which can be attributed to the electron spin of Cr³⁺inhibiting the emission of the R line produced by the ²E→⁴A₂transition.The best doping concentration of Cr³⁺is 2%,and the best holding time is 3h.When the Cr³⁺doping concentration is 0.5%,the chromaticity coordinates of AlF₃:Cr³⁺phosphor are（0.7136,0.2864）,and the fluorescence lifetime is 2.926ms.