Synthesis And Property Modulation Of Ca₉Ce?PO₄?₇ Series Fluorescence Materials For UV-near UV Light

In this research,a series of Ca₉Ce?PO₄?₇phosphors were synthesized by a high-temperature solid-state reaction method,which includes Ca_9-x-y Ce?PO₄?₇:xEu²⁺,yMn²⁺,Ca_8.78-x-y-z Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺,x Mg²⁺,y Sr²⁺,z Ba2+,Ca_8.78Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺,x H₃BO₃ and Ca_9-x Ce_0.5Y_0.5-u-v-w?PO₄?₇:xMn²⁺,u Tb³⁺,v Sm³⁺,w Eu³⁺.In these series phosphors,these methods including changing the variety and ratio of cations in host and doping fertilizer are used to control the phosphor's optical property.XRD pattern,fluorescence spectrum,fluorescence decay curve,chromaticity coordinate and color rendering index of the as-prepared samples are measured and used to characterize the properties.The specified influence caused by different adjusting methods to the phosphors luminescence property are investigated,and in the end the high color rendering index and high thermal stability white light emitting phosphors are acquired.The results are shown below:?1?The series Ca_9-x-yCe?PO₄?₇:x Eu²⁺,yMn²⁺ phosphors are synthesized by high-temperature solid-state reaction method.These characterization methods including excitation spectrum,emission spectrum fluorescence spectrum and so on are used to investigate the energy transfer effect between Ce³⁺-Eu²⁺?Ce³⁺-Mn²⁺ and Eu²⁺-Mn²⁺.The host will emit blue light under the 320 nm light excitation.The material will emit strong green light with increasing Eu²⁺ concentration in the host.The material will emit strong red light with increasingMn²⁺concentration in the host.Through adjusting the co-doping ratio of Eu²⁺ andMn²⁺,the luminescence color of the materials can change from blue green to white or jacinth when Eu²⁺/Mn²⁺are co-doping in the host.The chromaticity coordinate can change from?0.224,0.337?to?0.333,0.310?and to?0.550,0.294?.The white light emitted by Ca_8.88Ce?PO₄?₇:0.04Eu²⁺,0.08Mn²⁺is the high color rendering index warm white light,which color rendering index is 81 and the correlated color temperature is5446 K.This work will generate important meanings for the synthesis of single host multi-doping white light emission phosphors.?2?The series Ca_8.78-x-y-zCe?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺,x Mg²⁺,y Sr²⁺,z Ba²⁺phosphors are synthesized by high-temperature solid-state reaction method.Mg²⁺?Sr²⁺and Ba²⁺are used to substitute the Ca₂₊ in the host,thus the local crystal field environment ofluminescence center are changed under the condition of pure phase formation.The change of local crystal field environment includes the change of average bond length of luminescent center-ligand and the change of symmetry of the ligand polyhedron.The emission peak of Ce³⁺?Eu²⁺ andMn²⁺ will shift to a shorter wavelength when the bond length of the luminescent center-ligand becomes longer or the symmetry of the ligand polyhedron becomes stronger,and vice versa.In some cases,the effects respectively caused by the two factors are same for the shift of emission peak position,and in many cases,the two effects are opposite.The result is the comprehensive result produced by the two factors.In the host investigated in this paper,the influence produced by the change of symmetry of polyhedron is more obvious than that effect by the change of bond length between the luminescence center and its ligand.Changing the variety and ratio of cations will increase the distribution region of the chromaticity coordinates in the chromaticity diagram and improve the quantum efficiency of the samples.The internal quantum efficiency of Ca_8.78Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺ are 53.4%,and the that of Ca_7.98Ba_0.8Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺ are 49.5%.This control method will also improve the thermal stability of Eu²⁺ in some degrees.?3?The Ca_8.78Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺,x H₃BO₃ phosphors are synthesized by the high-temperature solid-state reaction method.The XRD patterns of the samples indicate that the doping of H₃BO₃ does not change the phase formation.The emission spectrum and fluorescence decay curve of samples indicate that the doping of H₃BO₃ can change the emission of Ce³⁺,Eu²⁺,Mn²⁺ and the energy transfer efficiency of Ce³⁺-Eu²⁺ ?Ce³⁺-Mn²⁺,The doping of H₃BO₃ can influence the ligand polyhedron volume of the luminescence center and the distance between luminescence centers in some degrees.In Ca_8.78Ce?PO₄?₇:0.06Eu²⁺,0.16Mn²⁺,x H₃BO₃,when the doping content of H₃BO₃ change from 0 to7,average volume of [?Eu/Mn?1/2/3-O] polyhedron change frome 27.511 ?³to21.847 ?³?The emission intensity of luminescence centers will increase when the ligand polyhedron volume decrease.When the distance between Ce³⁺-Eu²⁺and Ce³⁺-Mn²⁺,the energy transfer efficiency of them will increase.The doping of H₃BO₃ perfects the ration of red,green and blue colors,which improved the color rendering of the materials and changed the color rendering index from 80.5 to 90.7.The doping of H₃BO₃ will also improve the thermal stability of Eu²⁺in some degrees.The quenching temperature of Eu²⁺ are improved from 75 ? to 100 ?.?4?The Ca_9-x Ce_0.5Y_0.5-u-v-w?PO₄?₇:xMn²⁺,u Tb³⁺,v Sm³⁺,w Eu³⁺ phosphors are synthesized by the high-temperature solid-state reaction method.The XRD patterns of indicate that the synthesized samples are in pure phase formation.The excitation spectrum,emission spectrum and fluorescence decay curve of samples indicate that there exists energy transfer effect between Ce³⁺-Tb³⁺,Ce³⁺-Sm³⁺,Ce³⁺-Eu³⁺,Tb³⁺-Sm³⁺,Tb³⁺-Eu³⁺and Tb³⁺-Mn²⁺ in the series materials.The interaction mechanisms between Ce³⁺-Tb³⁺,Ce³⁺-Sm³⁺and Ce³⁺-Eu³⁺are dipole-dipole,dipole-dipole and quadrupole-quadrupole interactions,respectively.In order to acquire white light emission phosphors,the Ce³⁺,Tb³⁺and Sm³⁺/Eu³⁺/Mn²⁺are used to be blue,green and red light luminescence center,respectively.Thus,three kinds of combination mode Ce³⁺/Tb³⁺/Sm³⁺,Ce³⁺/Tb³⁺/Eu³⁺ and Ce³⁺/Tb³⁺/Mn²⁺are acquired.In these combination mode,only the Ce³⁺/Tb³⁺/Mn²⁺can produce high color rendering index and high thermal stability white light.The color rendering index of Ca_8.8Ce_0.5Y_0.5-x?PO₄?₇:0.17Tb³⁺,0.20Mn²⁺can be up to 80.2 and the quenching temperature is greater than 150?.