Tailoring of Deep‐Red Luminescence in Ca2SiO4:Eu2+

Satô, Yasushi; Kato, Hideki; Kobayashi, Makoto; Takeuchi, Masaki; Yoon, Dae Ho; Kakihana, Masato

doi:10.1002/anie.201402520

Cited by 216 publications

(162 citation statements)

References 25 publications

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“…12,50 Through the crystal-site engineering approach, we introduced Si 4+ −Ca 2+ into the CaYAlO 4 host to replace Al 3+ −Y 3+ attempting to shrink the AlO 6 octahedrons, accompanied by the expansion of CaO 9 polyhedron, then fulfilling the conditions for the reduction of Eu 3+ , because Si 4+ has a smaller radius than Al 3+ and substitution of Y 3+ by Ca 2+ can achieve charge compensation in the whole structure. 11,12,51 As the XRD pattern shows in Supporting Information Figure S3, impurities began to appear when x exceeded 0.30; thus, we restricted the x value to a maximum of 0.30. First, Rietveld refinement with GSAS program has been performed to reveal more details to clarify how substitution (Si 4+ −Ca 2+ for Al 3+ −Y 3+ ) affects the Ca 0.99+x Y 1−x Al 1−x Si x O 4 :Eu 0.01 (CYASO, x = 0−0.30) crystal structure and luminescence properties.…”

Section: Resultsmentioning

confidence: 99%

“…1−10 As compared to the all-LED devices, phosphors-converted white LEDs (pcWLEDs) have attracted much attention due to their fascinating merits, such as high color rendering index (CRI), high stability, and easy tunability of color temperatures. 4,7,11 Thus, the characteristic properties of the phosphors, including photoluminescence excitation (PLE) and emission wavelengths, thermal stability, and quantum efficiency, play a critical role in determine the luminous efficacy, color temperature, and color rendition of the WLEDs. It is essential to design some efficient phosphors for practical applications.…”

Section: Introductionmentioning

confidence: 99%

“…31−34 However, less research has been conducted on the reduction of Eu 3+ through crystal-site engineering approach by modifying the coordination environment and crystal site size of activators, to then fulfill the coexistence of luminescence from Eu 3+ and Eu 2+ in single phased phosphors. 11,12,35,36 Accordingly, it is a promising method to overcome the limitations of Eu 3+ activated phosphors via valence transfer, combined with the luminescence of Eu 2+ to obtain warm white light.…”

Section: Introductionmentioning

confidence: 99%

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Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

Zhang

et al. 2015

ACS Appl. Mater. Interfaces

189

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In this article, Eu-activated CaYAlO4 aluminate phosphors were synthesized by a solid-state reaction. Under UV light excitation, characteristic red line emission of Eu(3+) was detected in the range of 570-650 nm. In addition, we introduced crystal-site engineering approach into the CaYAlO4 host through incorporation of Si(4+)-Ca(2+) to replace Al(3+)-Y(3+), which would shrink the AlO6 octahedrons, accompanied by the expansion of CaO9 polyhedron, and then enable the partial reduction of Eu(3+) to Eu(2+). The crystal structure and underlying mechanism have been clarified on the basis of the Rietveld refinement analysis. The PL spectra of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) exhibit both green emission of Eu(2+) (4f(6)5d(1)-4f(7), broadband around 503 nm) and red-orange emission of Eu(3+) ((5)D0-(7)F1,2, 593 and 624 nm) under UV light excitation with a quantum yield of 38.5%. The CIE coordinates of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) phosphors are regularly shifted from (0.482, 0.341) to (0.223, 0.457) with increasing x, which would expand the application of Eu. Furthermore, this investigation reveals the correlations of structure and property of luminescent materials, which would shed light on the development of novel phosphors suitable for lighting and display applications.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

Zhang

et al. 2015

ACS Appl. Mater. Interfaces

189

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“…[6][7][8][9][10][11][12] Among these, calcium silicate hosts [6][7][8] have attracted considerable attention because of their various crystal structures (α, α' H , α' L , β and γ phases) 13 and therein crystallographically different calcium sites. Recently, Kalaji and co-workers have studied the photoluminescent (PL) behavior of the promising yellow γ-Ca 2 SiO 4 : Ce 3+ phosphors in detail, and also demonstrated the significance of a second dopant Al 3+ .…”

Section: Introductionmentioning

confidence: 99%

First-Principles Study on Structural, Electronic, and Spectroscopic Properties of γ-Ca₂SiO₄:Ce³⁺ Phosphors

et al. 2015

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In the present work, geometric structures, electronic properties, and 4f → 5d transitions of γ-Ca2SiO4:Ce(3+) phosphors have been investigated by using first-principles calculations. Four categories of typical substitutions (i.e., the doping of the Ce(3+) without the neighboring dopants/defects and with the neighboring VO(••), AlSi', and VCa″) are taken into account to simulate local environments of the Ce(3+) located at two crystallographically different calcium sites in the γ-Ca2SiO4. Density functional theory (DFT) geometry optimization calculations are first performed on the constructed supercells to obtain the information about the local structures and preferred sites for the Ce(3+). On the basis of the optimized crystal structures, the electronic properties of γ-Ca2SiO4:Ce(3+) phosphors are calculated with the Heyd-Scuseria-Ernzerhof screened hybrid functional, and the energies and relative oscillator strengths of the 4f → 5d transitions of the Ce(3+) are derived from the ab initio embedded cluster calculations at the CASSCF/CASPT2/RASSI-SO level. A satisfactory agreement with the available experimental results is thus achieved. Moreover, the relationships between the dopants/defects and the electronic as well as spectroscopic properties of γ-Ca2SiO4:Ce(3+) phosphors have been explored. Such information is vital, not least for the design of Ce(3+)-based phosphors for the white light-emitting diodes (w-LEDs) with excellent performance.

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“…There are mainly two approaches to find new phosphors; utilization of known compounds and their derivatives as hosts, 4 or exploration of new compounds. To discover new compounds, some research groups use their own methods.…”

mentioning

confidence: 99%

Synthesis, Structure, and Photoluminescence of a Novel Oxynitride BaYSi₂O₅N Activated by Eu²⁺ and Ce³⁺

Kobayashi¹,

Yasunaga²,

Sato³

et al. 2017

Chem. Lett.

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A novel oxynitride, BaYSi 2 O 5 N, has been synthesized by a solid-state reaction method. Its crystal structure was determined by single-crystal X-ray analysis. Eu 2+ -and Ce 3+-doped BaYSi 2 O 5 N exhibit broad blue emission with peaks around 459 and 412 nm under excitation at 250450 and 250370 nm, respectively. This is the first report on the synthesis of oxynitrides in the BaO-Y 2 O 3 -SiO 2 -Si 3 N 4 system. Keywords: Oxynitride | Phosphor | Novel compoundSolid-state lighting devices based on white light-emitting diodes (w-LEDs) rapidly became popular due to their advantages such as low energy consumption, long lifetime, less mercury usage, and compactness compared with those composed of conventional incandescent lamps and fluorescents.1,2 Brightness, whiteness, and other functional abilities of the most prevalent w-LEDs, that is, phosphor-converted w-LEDs, are strongly dependent on phosphors.2,3 Therefore, exploration of new phosphors is one of the important subjects in the fabrication of high-performance w-LEDs.There are mainly two approaches to find new phosphors; utilization of known compounds and their derivatives as hosts, 4 or exploration of new compounds. To discover new compounds, some research groups use their own methods. 511 Our group succeeded in the development of new compounds capable of hosts for Eu 2+ -activated phosphors with giving a contrast in the ionic radii of constituent ions by substitution of Sr 2+ or Ca 2+ for Ba 2+ in Ba 4 Al 2 S 7 or NaBaPO 4 , respectively. 9,10 On the other hand, oxynitrides are one of the promising host groups for phosphors because some oxynitrides such as SiAlON, Ba 3 Si 6 O 12 N 2 , and their related materials exhibit excellent luminescent properties, especially low thermal quencing.12 Based on the background described above, we searched for new oxynitride compounds with the concept of contrasts in constituent elements with respects to not only the ionic radii but also oxidation numbers ( Figure S1) N) was mixed. The pellets were put in a carbon crucible and calcined at 1573 K for 4 h under 100 mL min ¹1 of N 2 flow. After cooling to room temperature, they were ground into powders. To grow single crystals without any activator, after calcination at 1573 K for 4 h, it was slowly cooled to 1373 K at a rate of 25 K h ¹1 and to 1173 K at a rate of 50 K h ¹1. Colorless plate-like crystals were obtained and cut into pieces. One crystal with dimensions of 0.040 mm © 0.037 mm © 0.030 mm was used for single-crystal X-ray diffraction (XRD) analysis (Rigaku; R-AXIS RAPID II) using Mo Kα radiation at 296 K. The obtained powders were characterized by powder XRD analysis (Bruker AXS; D2 Phaser) and PL spectroscopy at room temperature (Hitachi; F-7100). Rietveld refinement was performed using the TOPAS 4.2 program (Bruker). The nitrogen contents in the samples were analyzed with an oxygen/ nitrogen analyzer (Horiba; EMGA-620W). Thermogravimetricdifferential thermal analysis (TG-DTA) was also conducted in air (Shimadzu; DTG-60H).The single-crystal XRD and nitrogen content ...

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Tailoring of Deep‐Red Luminescence in Ca₂SiO₄:Eu²⁺

Cited by 216 publications

References 25 publications

Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

First-Principles Study on Structural, Electronic, and Spectroscopic Properties of γ-Ca₂SiO₄:Ce³⁺ Phosphors

Synthesis, Structure, and Photoluminescence of a Novel Oxynitride BaYSi₂O₅N Activated by Eu²⁺ and Ce³⁺

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Tailoring of Deep‐Red Luminescence in Ca2SiO4:Eu2+

Cited by 216 publications

References 25 publications

Crystal-Site Engineering Control for the Reduction of Eu3+ to Eu2+ in CaYAlO4: Structure Refinement and Tunable Emission Properties

Crystal-Site Engineering Control for the Reduction of Eu3+ to Eu2+ in CaYAlO4: Structure Refinement and Tunable Emission Properties

First-Principles Study on Structural, Electronic, and Spectroscopic Properties of γ-Ca2SiO4:Ce3+ Phosphors

Synthesis, Structure, and Photoluminescence of a Novel Oxynitride BaYSi2O5N Activated by Eu2+ and Ce3+

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Tailoring of Deep‐Red Luminescence in Ca₂SiO₄:Eu²⁺

Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

Crystal-Site Engineering Control for the Reduction of Eu³⁺ to Eu²⁺ in CaYAlO₄: Structure Refinement and Tunable Emission Properties

First-Principles Study on Structural, Electronic, and Spectroscopic Properties of γ-Ca₂SiO₄:Ce³⁺ Phosphors

Synthesis, Structure, and Photoluminescence of a Novel Oxynitride BaYSi₂O₅N Activated by Eu²⁺ and Ce³⁺