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Title: Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution

Abstract

A range of Ca{sub 10.5-1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+}phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure ofβ-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+}, its emission undergoes a variation from violet–blue to cyan through introducing La{sup 3+}. The substitution of La{sup 3+} for Ca{sup 2+} could form some cation vacancies in Ca(4) sites according to the scheme 3Ca{sup 2+}= 2La{sup 3+}+ □ due to the different ion valence, which compels Eu{sup 2+} to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors. - Highlights: • Realizing photoluminescence control of Eu{sup 2+} by introducing relatively larger La{sup 3+} ion to replace the Ca{sup 2+} in β-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+} phosphor. • The mechanism of spectral control is proposed to be due to emptying of Ca{sup 2+} and migration of Eu{sup 2+}. • The thermal stability reduction is related to the formation of vacancies.

Authors:
; ; ; ; ; ; ;
Publication Date:
OSTI Identifier:
22658183
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 246; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM IONS; CALCIUM PHOSPHATES; CATIONS; EUROPIUM IONS; EXPERIMENTAL DATA; LANTHANUM IONS; PHOSPHORS; PHOTOLUMINESCENCE; RAMAN SPECTRA; SYNTHESIS; TEMPERATURE RANGE 0400-1000 K; VACANCIES; X RADIATION

Citation Formats

Fan, Yanting, Tang, Miao, Qiu, Zhongxian, Zhang, Jilin, Yu, Liping, Li, Chengzhi, Lian, Shixun, and Zhou, Wenli, E-mail: chemwlzhou@hunnu.edu.cn. Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution. United States: N. p., 2017. Web. doi:10.1016/J.JSSC.2016.11.026.
Fan, Yanting, Tang, Miao, Qiu, Zhongxian, Zhang, Jilin, Yu, Liping, Li, Chengzhi, Lian, Shixun, & Zhou, Wenli, E-mail: chemwlzhou@hunnu.edu.cn. Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution. United States. doi:10.1016/J.JSSC.2016.11.026.
Fan, Yanting, Tang, Miao, Qiu, Zhongxian, Zhang, Jilin, Yu, Liping, Li, Chengzhi, Lian, Shixun, and Zhou, Wenli, E-mail: chemwlzhou@hunnu.edu.cn. Wed . "Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution". United States. doi:10.1016/J.JSSC.2016.11.026.
@article{osti_22658183,
title = {Synthesis and photoluminescence control of Ca{sub 10.5–1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+} phosphors by aliovalent cation substitution},
author = {Fan, Yanting and Tang, Miao and Qiu, Zhongxian and Zhang, Jilin and Yu, Liping and Li, Chengzhi and Lian, Shixun and Zhou, Wenli, E-mail: chemwlzhou@hunnu.edu.cn},
abstractNote = {A range of Ca{sub 10.5-1.5x}La{sub x}(PO{sub 4}){sub 7}:Eu{sup 2+}phosphors were synthesized by high temperature solid state method. Subsequently we studied the crystal structures and luminescent properties through X-ray diffraction, photoluminescence and photoluminescence excitation, diffuse reflection spectra, Raman spectra and decay curves systematically. Based on the special crystal structure ofβ-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+}, its emission undergoes a variation from violet–blue to cyan through introducing La{sup 3+}. The substitution of La{sup 3+} for Ca{sup 2+} could form some cation vacancies in Ca(4) sites according to the scheme 3Ca{sup 2+}= 2La{sup 3+}+ □ due to the different ion valence, which compels Eu{sup 2+} to migrate from Ca(4) site to other sites. Additionally, the formation of the cation vacancies can further reduce the thermal stability of phosphors. - Highlights: • Realizing photoluminescence control of Eu{sup 2+} by introducing relatively larger La{sup 3+} ion to replace the Ca{sup 2+} in β-Ca{sub 3}(PO{sub 4}){sub 2}:Eu{sup 2+} phosphor. • The mechanism of spectral control is proposed to be due to emptying of Ca{sup 2+} and migration of Eu{sup 2+}. • The thermal stability reduction is related to the formation of vacancies.},
doi = {10.1016/J.JSSC.2016.11.026},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 246,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2017},
month = {Wed Feb 15 00:00:00 EST 2017}
}
  • Eu{sup 3+}-doped triple phosphate Ca{sub 8}MgR(PO{sub 4}){sub 7} (R=La, Gd, Y) was synthesized by the general high-temperature solid-state reaction. Excitation and emission spectra as well as luminescence decay were used to characterize the phosphors. Photoluminescence excitation and emission spectra showed that the phosphor could be efficiently excited by UV-vis light from 260 to 450 nm to give bright red emission assigned to the transition ({sup 5}D{sub 0}{yields}{sup 7}F{sub 2}) at 612 nm. The richness of the red color has been verified by determining their color coordinates (X, Y) from the CIE standard. - Graphical abstract: The RT luminescence spectra ofmore » Ca{sub 8}MgR(PO{sub 4}){sub 7} (R=La, Gd, Y) under 254 nm excitation using lamp source with the same conditions. The red emission lines at 612 nm originating from the electric dipole transition {sup 5}D{sub 0}-{sup 7}F{sub 2} is the dominant luminescence in the spectrum. It is found that the emission intensity of Eu{sup 3+} ions in Ca{sub 8}MgR(PO{sub 4}){sub 7} (R=La, Gd, Y) decreases in the sequence of R=Gd>Y>La.« less
  • A series of red-emitting phosphors Eu{sup 3+}-doped M{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} (M=Li, Na) have been successfully synthesized at 850 Degree-Sign C by solid state reaction. The excitation spectra of the two phosphors reveal two strong excitation bands at 396 nm and 466 nm, respectively, which match well with the two popular emissions from near-UV and blue light-emitting diode chips. The intensity of the emission from {sup 5}D{sub 0} to {sup 7}F{sub 2} of M{sub 2}(Gd{sub 1-x}Eu{sub x}){sub 4}(MoO{sub 4}){sub 7} phosphors with the optimal compositions of x=0.85 for Li or x=0.70 for Na is about five times higher thanmore » that of Y{sub 2}O{sub 3}:Eu{sup 3+}. The quantum efficiencies of the entitled phosphors excited under 396 nm and 466 nm are also investigated and compared with commercial phosphors Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} and Y{sub 3}A{sub 5}O{sub 12}:Ce{sup 3+}. The experimental results indicate that the Eu{sup 3+}-doped M{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7} (M=Li, Na) phosphors are promising red-emitting phosphors pumped by near-UV and blue light. - Graphical Abstract: The intensity of the red emission of M{sub 2}(Gd{sub 1-x}Eu{sub x}){sub 4}(MoO{sub 4}){sub 7} (M=Li, Na) phosphors with the optimal compositions is about five times higher than that of Y{sub 2}O{sub 3}:Eu{sup 3+}. Highlights: Black-Right-Pointing-Pointer Two novel Eu{sup 3+}-doped red phosphors (Na{sub 2}Gd{sub 4}(MoO{sub 4}){sub 2}, Li{sub 2}Gd{sub 4}(MoO{sub 4}){sub 7}) were synthesized. Black-Right-Pointing-Pointer Their emission intensities are about five times higher than that of Y{sub 2}O{sub 3}:Eu{sup 3+}. Black-Right-Pointing-Pointer Their quantum efficiencies are higher than that of commercial red phosphor Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+}.« less
  • The relationship between the photoluminescence properties and the crystal structure of undoped, Eu{sup 3+} or/ and Tm{sup 3+} singly or codoped Ca{sub 9}La(VO{sub 4}){sub 7} (CLaVO) samples was discussed. Under the excitation of UV light, CLaVO:Tm{sup 3+}, CLaVO, and CLaVO:Eu{sup 3+} exhibit the characteristic emissions of Tm{sup 3+} ({sup 1}G{sub 4}→{sup 3}H{sub 6}, blue), O{sup 2−}→V{sup 5+} charge transfer (CT), and Eu{sup 3+} ({sup 5}D{sub 0}→{sup 7}F{sub 2}, red), respectively. By adjusting the doping concentration of Tm{sup 3+} and Eu{sup 3+} ions in CLaVO, a natural white emission in a single composition with the color temperature at 6181 K wasmore » obtained. Based on the dielectric theory of complex crystal, the chemical bond parameters of La-O and V-O bonds were quantitatively calculated. The standard deviation of environmental factor of every bond (EFSD), which can be expressed as σ(h{sub e{sub i}})=√((1/N)∑{sub i=1}{sup N}(h{sub e{sub i}}−μ){sup 2}) (h{sub e{sub i}}=(f{sub c{sub i}}α{sub b{sub i}}){sup 1/2}Q{sub B{sub i}} and μ=(1/N)∑{sub i=1}{sup N}h{sub e{sub i}}), was proposed to quantitatively express the distortion degree of VO{sub 4}{sup 3−} from that of an ideal tetrahedron. The maximum change of EFSD comes from the [VO{sub 4}]{sup −} tetrahedra in CLaVO sample by comparison with that of EFSD of isostructural Ca{sub 9}Gd(VO{sub 4}){sub 7}. This is possible the key reason that the undoped CLaVO sample has self-activated emission while the self-activated emission of its isostructural Ca{sub 9}Gd(VO{sub 4}){sub 7} sample cannot be found. The quantitative calculation also demonstrated that the broad excitation bands at 319 nm in CLaVO:Tm and at 335 nm in CLaVO:Eu were due to the O-V2 and O-V3 (overlap with O-V2) CT, not the CT energy of O{sup 2−}-Eu1{sup 3+} (O{sup 2−}-Tm1{sup 3+}), O{sup 2−}-Eu2{sup 3+} (O{sup 2−}-Tm2{sup 3+}), and O{sup 2−}-Eu3{sup 3+} (O{sup 2−}-Tm3{sup 3+}). The environmental factors surrounding the atoms V1, V2 and V3 were calculated to be 1.577, 1.6379 and 1.7554, respectively. It can be demonstrated that the excitation spectra at 319 nm for CLaVO:Tm and 335 nm for CLaVO:Eu came from the O-V2 and O-V3 CT, respectively. - Graphical abstracts: The relationship between the photoluminescence properties and the crystal structure of undoped, Eu{sup 3+} or/ and Tm{sup 3+} singly or codoped Ca{sub 9}La(VO{sub 4}){sub 7} (CLaVO) samples was discussed experimentally and theoretically. - Highlights: ●The photoluminescence properties of Ca{sub 9}La(VO{sub 4}){sub 7}:Eu, Tm were measured. ●The tunable color including white emission can be obtained. ●The important chemical bond parameters of O-V were calculated quantitatively. ●The standard deviation of environmental factor of every bond was proposed. ●The theoretical analysis of the self-activated emission for Ca{sub 9}La(VO{sub 4}){sub 7} was given.« less
  • Graphical abstract: Emission spectra and CIE chromaticity diagram of the (Y{sub 0.9−x}La{sub x})Eu{sub 0.1}VO{sub 4} phosphor. - Highlights: • The CIE chromaticity of (Y{sub 0.75}La{sub 0.15})Eu{sub 0.1}VO{sub 4} phosphor is (0.66, 0.34). • The D{sub 0} → {sup 7}F{sub 2} transition intensity increases about five times for the 15 mol% of La{sup 3+} ion doping. • The (Y{sub 0.75}La{sub 0.15})Eu{sub 0.1}VO{sub 4} may be suitable for use as a UV-LED converted phosphor. - Abstract: The (La, Eu) co-doped YVO{sub 4} with nano-crystal phosphors were prepared using a sol–gel method. The X-ray diffraction profiles show that all of the peaks aremore » attributed to the YVO{sub 4} phase when co-doped with the (La{sup 3+}, Eu{sup 3+}) ions. The intensities of the diffraction peaks decreases when the La{sup 3+} ion concentrations increase. In addition, under an excitation of 318 nm, the {sup 5}D{sub 0} → {sup 7}F{sub 2} transition intensity increased with increasing the La{sup 3+} ion concentration, and increased about five with the 15 mol% of La{sup 3+} ion doping. This is caused by the large difference in ion radius between the La{sup 3+} and Y{sup 3+} ions, which leads to a distorted lattice and a local nonuniform strain in the vicinity of the Eu{sup 3+} ions when La{sup 3+} ions substitute Y{sup 3+} ions in the (Y{sub 0.9−x}La{sub x})Eu{sub 0.1}VO{sub 4} system. The bright red emission of the (Y{sub 0.9}Eu{sub 0.1})VO{sub 4} phosphor has the CIE chromaticity coordinates of (0.66, 0.34) with 15 mol% La{sup 3+} ion doping, which is very close to the NTSC system standard red chromaticity coordinates of (0.67, 0.33)« less
  • Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{submore » 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1−x}Ln{sub x} in one of the two Sr sites. • Mn{sup 3+}/Mn{sup 4+} magnetic ions are spatially arranged in a triangular kagomé fashion. • Enhanced ferromagnetic ordering attributed to doping non-Jahn–Teller Mn{sup 4+}.« less