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Title: Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si 6–zAl zO zN 8–z:Eu 2+ phosphors

Abstract

Inorganic phosphor materials play a crucial role in the creation of white light from blue and near-UV solid-state light-emitting diodes. Understanding the intricacies of the phosphor structure is key for setting the stage for improved, more efficient functionality. Average structure and coordination environment analysis of the robust and efficient green-emitting phosphor, β-SiAlON:Eu 2+ (β-Si 6–zAl zO zN 8–zEu 0.009), is combined here with a range of property measurements to elucidate the role of Al content ( z) in luminescence properties, including the red shift of emission and the thermal quenching of luminescence as a function of increasing Al content z. Average structure techniques reveal changes in polyhedral distortion with increasing z for the 9-coordinate Eu site in β-SiAlON:Eu 2+. X-ray absorption near edge structure (XANES) is used to confirm that the majority of the activator Eu is in the Eu 2+ state, exhibiting the symmetry-allowed and efficient 4f 75d 0 → 4f 65d 1 transitions. As a result, room temperature and temperature-dependent luminescence indicate a curious increase in thermal stability with increasing z over a small range due to an increasing barrier for thermal ionization, which is correlated to an increase in the quantum yield of the phosphor.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1];  [1];  [1];  [3]; ORCiD logo [1]
  1. Univ. of California, Santa Barbara, CA (United States)
  2. Bates College, Lewiston, ME (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC)
OSTI Identifier:
1399266
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Materials Chemistry. C
Additional Journal Information:
Journal Volume: 5; Journal Issue: 38; Journal ID: ISSN 2050-7526
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Cozzan, Clayton, Laurita, Geneva, Gaultois, Michael W., Cohen, Marcus, Mikhailovsky, Alexander A., Balasubramanian, Mahalingam, and Seshadri, Ram. Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si6–zAlzOzN8–z:Eu2+ phosphors. United States: N. p., 2017. Web. doi:10.1039/C7TC03039H.
Cozzan, Clayton, Laurita, Geneva, Gaultois, Michael W., Cohen, Marcus, Mikhailovsky, Alexander A., Balasubramanian, Mahalingam, & Seshadri, Ram. Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si6–zAlzOzN8–z:Eu2+ phosphors. United States. doi:10.1039/C7TC03039H.
Cozzan, Clayton, Laurita, Geneva, Gaultois, Michael W., Cohen, Marcus, Mikhailovsky, Alexander A., Balasubramanian, Mahalingam, and Seshadri, Ram. 2017. "Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si6–zAlzOzN8–z:Eu2+ phosphors". United States. doi:10.1039/C7TC03039H.
@article{osti_1399266,
title = {Understanding the links between composition, polyhedral distortion, and luminescence properties in green-emitting β-Si6–zAlzOzN8–z:Eu2+ phosphors},
author = {Cozzan, Clayton and Laurita, Geneva and Gaultois, Michael W. and Cohen, Marcus and Mikhailovsky, Alexander A. and Balasubramanian, Mahalingam and Seshadri, Ram},
abstractNote = {Inorganic phosphor materials play a crucial role in the creation of white light from blue and near-UV solid-state light-emitting diodes. Understanding the intricacies of the phosphor structure is key for setting the stage for improved, more efficient functionality. Average structure and coordination environment analysis of the robust and efficient green-emitting phosphor, β-SiAlON:Eu2+ (β-Si6–zAlzOzN8–zEu0.009), is combined here with a range of property measurements to elucidate the role of Al content (z) in luminescence properties, including the red shift of emission and the thermal quenching of luminescence as a function of increasing Al content z. Average structure techniques reveal changes in polyhedral distortion with increasing z for the 9-coordinate Eu site in β-SiAlON:Eu2+. X-ray absorption near edge structure (XANES) is used to confirm that the majority of the activator Eu is in the Eu2+ state, exhibiting the symmetry-allowed and efficient 4f75d0 → 4f65d1 transitions. As a result, room temperature and temperature-dependent luminescence indicate a curious increase in thermal stability with increasing z over a small range due to an increasing barrier for thermal ionization, which is correlated to an increase in the quantum yield of the phosphor.},
doi = {10.1039/C7TC03039H},
journal = {Journal of Materials Chemistry. C},
number = 38,
volume = 5,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
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  • Ce{sup 3+},Li{sup +}-codoped Ca-{alpha}-Sialon phosphors with the formula [Ca{sub (1-2x)}Ce{sub x}Li{sub x}]{sub m/2}Si{sub 12-(m+n)}Al{sub m+n}O{sub n}N{sub 16-n} (0{<=}x{<=}0.25, 0.5{<=}m{<=}3.5, and 0.16{<=}n{<=}2.0) have been synthesized by gas pressure sintering (GPS). The effects of the activator concentration and the overall composition of host lattice on the phase evolution, morphology, and optical properties were investigated. The single-phase Ca-{alpha}-Sialon:Ce{sup 3+},Li{sup +} can be synthesized at x<0.1, 1.0{<=}m{<=}2.5, and n{<=}1.2. The synthesized powders exhibit a relatively dispersive and uniform morphology. Under the near UV excitation, the bright green-blue emission centered at 500-518 nm is observed. The photoluminescence can be tailored by controlling Ce{sup 3+} concentrationmore » and the overall composition of the {alpha}-Sialon host lattice. With increasing the Ce concentration and m value both excitation and emission bands show a red shift, which perfectly matches with the near-UV LEDs in the range of 360-410 nm. The strongest luminescence is achieved at x=0.08-0.1, m=2.0-2.5, and n=1.0. Simultaneously, the highest quantum efficiency and better thermal stability are also present. -- Graphical abstract: Dependence of photoluminescence intensity and normalized photoluminescence spectra (the inset) of Ca-{alpha}-Sialon:Ce{sup 3+},Li{sup +} on the host lattice composition: (a) m value and (b) n value Display Omitted Highlights: {yields} The optical properties of [Ca{sub (1-2x)}Ce{sub x}Li{sub x}]{sub m/2}Si{sub 12-(m+n)}Al{sub m+n}O{sub n}N{sub 16-n} (0{<=}x{<=}0.25, 0.5{<=}m{<=}3.5, 0.16{<=}n{<=}2.0) have been investigated. {yields} Excited by near UV, the bright green emission centered at 500-518 nm is observed. {yields} The photoluminescence can be tailored by controlling Ce{sup 3+} content and host lattice composition. {yields} The strongest luminescence is achieved at x=0.08-0.1, m=2.0-2.5, and n=1.0. {yields} The highest quantum efficiency and better thermal stability are also present.« less
  • Graphical abstract: A yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was firstly synthesized by the solution-combustion method. The photoluminescence excitation and emission spectra, temperature dependence of luminescence intensity, and luminescence lifetime of the phosphor were investigated. Highlights: Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was synthesized by a solution-combustion method. Black-Right-Pointing-Pointer Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). Black-Right-Pointing-Pointer The temperature dependent luminescence property and mechanism of Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} were studied. -- Abstract: Yellow-emitting phosphor Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} was synthesized by a solution-combustion method. Themore » phase structure and microstructure were determined by the X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis, respectively. The as-prepared Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor absorbed near ultraviolet and blue light of 320-500 nm, and showed an intense yellow emission band centered at 569 nm with the CIE coordinate of (0.453, 0.526). The lifetime of Eu{sup 2+} ions in Ca{sub 2}BO{sub 3}Cl:Eu{sup 2+} phosphor was measured, furthermore the temperature dependent luminescence property and mechanism were studied, which also testified that the present phosphor had a promising potential for white light-emitting diodes.« less
  • It is shown that with simultaneous external damping and recombination interactions of centers, the luminosity of the activator bands depends on the intensity of the excitation. The dependence is of such a nature that it may be accounted fur by two co-multipliers, one of which is determined by the external damping and the other by the recombination:nteractions. The obtained formulas are used for determiaing the effects of temperature and activator concentration on each luminosity band. (R.V.j.)
  • Graphical abstract: A comparative study on the concentration quenching behaviors of green down- and up-conversion emissions was carried out for the first time, and the different concentration quenching mechanisms were analyzed. Secondly, the thermal effect induced by 980 nm LD irradiation was investigated, it was observed that the equilibrium temperature of Gd{sub 2}(WO{sub 4}){sub 3}:Er{sup 3+}/Yb{sup 3+} sample was decided by both the excitation power and Er{sup 3+} doping concentration. Highlights: ► Gd{sub 2}(WO{sub 4}){sub 3}:Er/Yb phosphors were prepared via a co-precipitation reaction. ► Morphology and structure of the phosphors were characterized by XRD and SEM. ► Concentration quenching mechanismsmore » for down and up emissions were studied. ► Thermal effect induced by laser irradiation was studied via temperature sensing tech. - Abstract: Gd{sub 2}(WO{sub 4}){sub 3} phosphors with various Er{sup 3+} concentrations and fixed Yb{sup 3+} concentration were synthesized via a co-precipitation method, and their crystal structure and morphology were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The concentration quenching behaviors of green up- and down-conversion emissions of Er{sup 3+} were analyzed, and it was confirmed that the difference between quenching concentration for up- and down-conversion emissions resulted from the different population routes. The temperature sensing properties of the Gd{sub 2}(WO{sub 4}){sub 3}:Er{sup 3+}/Yb{sup 3+} phosphors were studied, and it was found that the Er{sup 3+} doping concentration slightly affected the sensitivity, and Gd{sub 2}(WO{sub 4}){sub 3}:Er{sup 3+}/Yb{sup 3+} phosphors could be used in a broad temperature region for detecting temperature. Finally, the thermal effect induced by 980 nm LD irradiation was investigated, it was observed that the equilibrium temperature of Gd{sub 2}(WO{sub 4}){sub 3}:Er{sup 3+}/Yb{sup 3+} sample was decided by both the excitation power and Er{sup 3+} doping concentration.« less