Subscriber access provided by UNIV AUTONOMA DE COAHUILA UADEC
Article 1-x
x
3
4
2+
Chemical Control of SrLi(Al Ga)N:Eu Red Phosphor at Extreme Condition for the Application in Light-emitting Diodes Mu-Huai Fang, Shu-Yi Meng, Natalia Majewska, Tadeusz Lesniewski, Sebastian Mahlik, Marek Grinberg, Hwo-Shuenn Sheu, and Ru-Shi Liu Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.9b01783 • Publication Date (Web): 28 May 2019 Downloaded from http://pubs.acs.org on May 28, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Chemistry of Materials
Chemical Control of SrLi(Al1-xGax)3N4:Eu2+ Red Phosphor at Extreme Condition for the Application in Light-emitting Diodes Mu-Huai Fang,† Shu-Yi Meng,† Natalia Majewska,§ Tadeusz Leśniewski,§ Sebastian Mahlik,§ Marek Grinberg,§ Hwo-Shuenn Sheu,¥ and Ru-Shi Liu*,†,‡ †Department
of Chemistry, National Taiwan University, Taipei 106, Taiwan of Experimental Physics, Faculty of Mathematic, Physics and Informatics, Gdańsk University, Wita Stwosza 57, 80-308 Gdańsk, Poland ¥National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan ‡Department of Mechanical Engineering and Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei 106, Taiwan §Institute
ABSTRACT: Phosphor materials are promising candidates for white light-emitting diode applications. High-quality phosphor materials must be synthesized under extreme conditions. In this study, a series of SrLi(Al1-xGax)3N4:Eu2+ (GSLA) narrow-band emission red phosphors are successfully synthesized under 1,000 atm nitrogen gas atmosphere through the hot isostatic press, which cannot be achieved under low pressure. Successful Ga incorporation is confirmed by X-ray diffraction and Rietveld refinement. Phonon repetition structure and detailed thermal properties are analyzed by temperature-dependent photoluminescence intensity and lifetime. The structural ordering and rigidity are comprehensively evaluated by Raman spectra. The blueshift of the photoluminescence spectra enhances the luminous efficacy of radiation, making GSLA a potential candidate for practical application. This study promotes the research on materials synthesized under extreme conditions and the development of novel phosphor materials.
With progress for several centuries, lighting application has shifted from simple daily use to high-standard devices. Lightemitting diodes (LEDs) have become mainstream in this field. Phosphors, which are the basic materials in LED, determine the color of the LED devices and affect their color rendition.1-3 Narrowband emission phosphor should be selected to achieve highstandard devices with excellent color rendition. Among all the colors, the red component shows the largest area for improvement. Schnick et al.4-7 developed numerous nitride phosphors with narrow-band emission. Among nitride phosphors, SrLiAl3N4:Eu2+ (SLA) is the most outstanding and has acceptable emission intensity, extremely narrow emission bandwidth, and excellent thermal stability. SLA loses less than 5% of luminescence intensity at 200 °C compared with that at room temperature. Nevertheless, SLA has two distinct disadvantages. One is chemical stability, which was already solved by a previous study via surface coating.8 The other is its emission wavelength at around 650 nm, which is close to the insensitive region in the human eye and could increase the waste–photon ratio.9 As a solution, the Ga-doped SLA phosphor with the blue-shifted emission was synthesized. However, different
from SLA, SrLi(Al1-xGax)3N4:Eu2+ (GSLA) synthesis failed under atmospheric N2 pressure, which can only be synthesized through the hot isostatic press (HIP). A previous study revealed the advantage of using high-pressure synthesis, which can significantly enhance the quantum efficiency.10 In other works, phosphors, such as SrAlSiN3:Eu2+, cannot be synthesized under the abovementioned condition but only through the use of pressure higher than 100 MPa (approximately 1000 atm.).11-12 Therefore, extreme conditions should be applied to synthesize special phosphor materials. In this study, a series of SrLi(Al1-xGax)3N4 (GSLA) is synthesized through the HIP. Photoluminescence (PL) spectra show a blue shift in the crystal of SLA during Ga substitution. The crystal structure of the GLSA is also well examined by synchrotron X-ray diffraction and Rietveld refinement. Moreover, its thermal properties are analyzed by temperature-dependent PL and lifetime. Finally, structural ordering and rigidity are comprehensively checked by Raman spectra. The X-ray diffraction (XRD) patterns of the GSLA are shown in Figure S1. The host of SLA belongs to the triclinic system with the space group of P1. Li+ and Al3+ form the LiN4 and AlN4 tetrahedrons, respectively, and constitute the channel structure. Sr ions are found in the channel and coordinated by the cuboid environment. For GSLA, Ga is substituted in the Al sites to form the solid solution, whereas Eu is substituted in the Sr sites. The XRD peaks shift toward the low angle. Furthermore, the GSLA undergoes Rietveld refinement to understand its basic information (Figure 1a and 1b). The lattice parameters, including a, b, c, and volume, follow Vegard’s law of linearly increasing due to the larger cation size of Ga (0.47 Å, IV) compared with that of Al (0.39 Å, IV) as shown in Figure 1c and Table S1.13 Some AlN impurities are detected in the XRD patterns. The peaks of AlN also shift toward a low angle during the incorporation of Ga ions, indicating the existence of (Al1-xGax)N impurity. Although GSLA is successfully synthesized via the HIP system, the intensity of (Al1-xGax)N impurity peaks in XRD patterns rapidly increase with the doping of Ga ions. This result indicates that gas pressure promotes the doping of Ga but within some limitations.
ACS Paragon Plus Environment
Chemistry of Materials
Page 2 of 5 ∞
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Ф𝑣 = 683.002 𝑙𝑚/𝑊 ·∫0 𝑦(𝜆)Ф𝑒,𝜆 𝑑𝜆,
Figure 1. Rietveld refinement of (a) SrLiAl3N4:Eu2+ and (b) SrLi(Al0.9Ga0.1)3N4:Eu2+. (c) Lattice parameters of SrLi(Al12+ xGax)3N4:Eu . PL and photoluminescence excitation (PLE) spectra are measured to understand the luminescent properties of GSLA. PLE is characterized by broadband absorption in the range of 400 nm to 600 nm in relation to the transition from the 4f7(8S7/2) ground state to the 4f65d excited state (Figure S2). The maximum peak of the excitation spectra is at approximately 470 nm, which indicates that GSLA can be efficiently excited by the 460 nm blue LED chips. The PL spectrum of Eu2+ (Figure 2a) is related to the transition from the lowest excited state (4f65d1) to the ground state of the Eu2+ with the maximum peak at 655 nm for SLA. When incorporated with Ga, the blue shift in the emission is observed. This result reveals the benefit of enhancing the brightness due to the high sensitivity of the human eye for wavelengths shorter than 650 nm. The increasing of the PL energy is related to diminishing of the crystal field strength and lowering the splitting of the 4f65d electronic manifold. As a result of the energy of the lowest state of 4f65d increases. Additionally, compared with Al, Ga has lower covalence effect.14 Both effects lead to the shorter emission wavelength. The detailed PL information and quantum efficiency are shown in Table S2 and Table S3. The full-width at half-maximum (FWHM) is approximately 56–59 nm for all samples. However, if the unit of FWHM is converted from nanometer to wavenumber, then the FWHM increases from 1281 cm−1 to 1462 cm−1 for x = 0 to 0.6. This result also reveals the importance of using the energy scale when considering the bandwidth. Moreover, the broadening of the PL spectrum illustrates the inhomogeneous environment of the Eu2+ coordinated environment. The room temperature (RT) decay profiles of SrLi(Al1-xGax)3N4:Eu2+ are shown in Figure S3. PL is excited with 470 nm and then monitored at the emission maximum for various dopant concentrations. Decay profiles are obtained from the entire spectral range of the luminescence. For SLA and low-Ga GSLA (x = 0.033) samples, the RT decay curve is two exponential, whereas for high-Ga GSLA (x = 0.5), the curve is multi-exponential with rapid decay. The luminous efficiency of radiation (LER) and relative LER across the PL intensity are shown in Figure 2b to further understand the benefit of Ga incorporation. LER can be calculated as follows:15 𝐾=
Фv
= Фe
∞
∫0 𝐾(𝜆)Ф𝑒,𝜆 𝑑𝜆 ∞
∫0 Ф𝑒,𝜆 𝑑𝜆
,
(1)
(2)
where Фe is the radiant flux, Фv is the luminous flux, 𝑦 is the eye sensitivity curve, and Фe,λ is the luminous spectrum. The theoretical LER of the 555 nm green light is 683 lm/W and decreases when the wavelength of the light diverges. Owing to the deep-red emission with the wavelength at 650 nm (655 nm in our case), the LER is only around 60 lm/Wopt but increases to nearly 80 lm/Wopt when 10% of Ga is doped. The peak is apparently shortened, leading to the large enhancement of the LER (210 lm/Wopt as x = 0.6). However, LER only considers the emission wavelength and the peak shape, which cannot represent the practical performance of the phosphors. Hence, the relative value of LER across PL intensity is also calculated. Although the wavelengths of SLA and SrLi(Al0.9Ga0.1)3N4:Eu2+ are close to each other, the values can increase around the deep-red color when the emission peak slightly shifts to the short wavelength. From the calculation, SrLi(Al0.9Ga0.1)3N4:Eu2+ gains 125% of LER*(PL Int.) compared with that of SLA. With the high x value, the LER*(PL Int.) starts to decrease due to the weak PL intensity. However, for x = 0.2 and 0.3, the value is still higher than the SLA itself. This finding illustrates the advantage of the blue shift of the PL spectra during Ga doping. The main reason for the decrease in PL intensity is the impurity of (Al1-xGax)N during synthesis.
Figure 2. (a) Photoluminescence spectra and (b) LER and LER*PL of SrLi(Al1-xGax)3N4:Eu2+. Temperature-dependent photoluminescence (TDPL) spectra are measured to understand the thermal properties of GSLA (Figure 3a). For SLA, the emission intensity at 200 °C can produce 98% of the intensity at low temperature, which shows extremely good thermal stability and is in line with the findings in the literature.6 By contrast, the thermal stability of GSLA continuously decreases when the Ga concentration increases. This result might be attributed to the decrease in band gap during Ga doping. The reduce band gap consequently decreases the energy difference between the lowest 4f65d1 state and the conduction band, thus enhancing the
ACS Paragon Plus Environment
2
Page 3 of 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Chemistry of Materials photoionization. Furthermore, the asymmetric feature is observed in the TDPL contour plot of SrLi(Al0.4Ga0.6)3N4:Eu2+ (Figure 3b), revealing the distinct differences in thermal stability for the two Eu2+ sites. The temperature dependence of average decay time of GSLA upon excitation at 470 nm is comprehensively analyzed in the temperature range from 10 K to 500 K. The average decay times τ for these decay profiles are calculated using the following formula: 𝜏=
∫𝐼(𝑡)𝑡𝑑𝑡 ∫𝐼(𝑡)𝑑𝑡
,
(3)
where I(t) is the intensity of luminescence. The average decay time at 10 K is almost the same for x = 0 and x = 0.033 samples (0.55–0.56 μs), which is long for x = 0.5 sample (0.47 μs). For x = 0 and x = 0.033, the average decay time increases with the temperature between 10 K and 400 K and starts to decrease at temperatures higher than 400 K (Figure 3c). This finding is due to the fact that at low temperature only spin allowed transition from the lowest df state occurs and the luminescence probability of transition from this state to the ground state 8S7/2 (spin 7/2) from 4f7 configuration is the highest. When the temperature increases, apart of the emission from the above-mentioned excited df state, the higher excited states which have spin equal to 5/2 (due to the opposite spin of d electron) are occupied. Since the transition from these states is forbidden, thereby lengthening the decay time. Consequently, the decay time, which is the average time of all radiative transitions, is prolonged for high temperature. Thermal quenching starts at 400 K for x = 0 and 0.033, and the decay time is shortened. By contrast, for x = 0.5 sample, the quenching process and the phenomenon described above simultaneously occur (Figure 3d). One process causes elongation, whereas the other reduces the decay time. Consequently, a decay time that shows no changes up to 200 K and is strongly shortened above 200 K is obtained. At this time, the quenching process begins to dominate.
not appear. This phonon repetition structure is also discovered in some other phosphor materials with high rigidity, such as low oxygen-contained (low-z) β-SiAlON system.16-17 The high rigidity of the structure with condensation degree κ equaling to unity may also improve its luminescent property. With increasing temperature, the emission bands are broadened for all measured samples: x = 0, 0.033, 0.5. The temperature increase in the bandwidth is evident and almost the same for x = 0 and 0.033 samples but is considerably small for x = 0.5. Figure 4d shows the emission spectra for x = 0, 0.033, 0.5 upon excitation at 473 nm in 10 and 300 K. The bandwidth and the shape of emission spectra for x = 0 and 0.033 are respectively similar at 10 and 300 K, whereas the emission bandwidth for x = 0.5 is wide and shifts to the blue region with respect to the PL for x = 0 and 0.033. The lack of phonon structure in the PL spectrum for high Ga content is attributed to the inhomogeneous broadening of the PL spectra. This phenomenon can also explain the broader bandwidth of x = 0.5 at 10 K as compared with that of x = 0 and 0.33. For x = 0.5, the inhomogeneous broadening affects the domains in the bandwidth at low temperature. Even when the thermal broadening effect at low temperature is diminished, the bandwidth is still broad.
Figure 4. TDPL of SrLi(Al1-xGax)3N4:Eu2+ for (a) x = 0, (b) x = 0.033, and (c) x = 0.5 upon excitation at 473 nm in temperature ranges from 10 K to 350 K. (d) PL spectra of SrLi(Al12+ xGax)3N4:Eu for x = 0, 0.033, 0.5 upon excitation at 473 nm in 10 and 300 K.
Figure 3. (a) Relative TDPL intensity of SrLi(Al1-xGax)3N4:Eu2+. (b) TDPL contour plot of SrLi(Al0.4Ga0.6)3N4:Eu2+. Temperature dependence of average decay time of SrLi(Al1-xGax3)N4:Eu2+ upon excitation at 470 nm in temperature range from 10 to 500 K for (c) x = 0, 0.033, and (d) x = 0.5. The low-temperature PL spectra and decay curve of SLA, low-Ga (x = 0.033), and high-Ga (x = 0.5) samples upon excitation at 473 nm at a temperature from 10 to 350 K area are measured to further understand the behavior of their thermal properties (Figure 4). For SLA, the peak structures from 625 nm to 675 nm are observed for temperature between 10 and 150 K (Figure 4a), which is well resolved by diminishing thermal broadening at low temperature. For small gallium x = 0.033, the peak structure is no longer visible (Figure 4b), whereas that for x = 0.5 (Figure 4c) does
The Raman spectra of GSLA are measured and shown in Figure 5a to understand its rigidity and ordering properties. The modes ranging 400–800 cm−1 correspond to the bending and internal stretching vibration of the LiN4 and Al(Ga)N4 tetrahedrons, respectively.18 The peaks do not remarkably change when the Ga concentration increases, indicating that the phosphors maintain the SLA structure as shown in the XRD. For SLA (x = 0), the alignment of the LiN4 and AlN4 tetrahedrons conforms to the high rigidity of the structure. Therefore, clear sharp peaks can be observed in the Raman spectrum. Moreover, the peak with high intensity at 460 and 490 cm−1 corresponds to the rotational vibration mode of the external lattice.18 Owing to the heavier atomic weight of Al compared with that of Li, the peaks at 460 and 490 cm−1 can be respectively assigned to AlN4 and LiN4. By contrast, with Ga incorporation into the SLA (x = 0.5), the sharp peaks gradually merge and broaden. Consequently, the system changes from ordering to disordering structure.19 Incorporating Ga has a considerably higher effect on the peak at 460 cm−1 than that at 490 cm−1, indicating that Ga is substantially doped into the Al sites and destroys the ordering structure. The peak at 540 cm−1 also shifts
ACS Paragon Plus Environment
3
Chemistry of Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
toward low energy during Ga doping due to its heavy atomic weight.20 The schematic graph of coordinated tetrahedron environment of Sr2+ ions is shown in Figure 5b. Numerous tetrahedron combinations are possible for Sr coordinated environment, leading to disordered and inhomogeneous structures. This effect results in the broadening of the PL spectra and the disappearance of the phonon repetition structure of PL spectra at 10 K.
Page 4 of 5
■ ACKNOWLEDGMENTS This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 107-2113-M-002008-MY3 and MOST 107-2923-M-002-004-MY3), the National Science Center Poland Grant Opus (No. 2016/23/B/ST3/03911), and the National Center for Research and Development Poland Grant (No. PL-TW/V/1/2018).
■ REFERENCES (1) (2) (3) (4)
(5)
(6)
(7)
Figure 5. (a) Raman spectrum of SrLi(Al1-xGax)3N4:Eu2+ for x = 0, 0.033, and 0.5. (b) Schematic graph of coordinated tetrahedron environment of Sr2+ ions. In summary, a series of SrLi(Al1-xGax)3N4:Eu2+ red phosphors are successfully synthesized under the extreme condition of 1,000 atm nitrogen gas atmosphere through the hot isostatic press. The structures are carefully examined to confirm the successful incorporation of Ga ions. The blueshift of the PL spectra and the calculated LER*(PL Int.) reveal the benefits of adding Ga into the SLA host. TDPL and Raman spectra show the thermal properties of the two Ga sites and provide new insights into their structure ordering and rigidity properties. This study presents the path to uniquely developing novel phosphor materials and helps researchers understand the structure ordering properties of a complicated structure.
(8)
(9) (10) (11) (12)
■ ASSOCIATED CONTENT Supporting Information
(13)
Supporting Information is available free of charge via the Internet at http://pubs.acs.org.
(14)
Experimental methods; Refinement data; Photoluminescence excitation spectrum; Quantum efficiency.
(15)
■ AUTHOR INFORMATION (16)
Corresponding Author
[email protected] Notes The authors declare no competing financial interest. Mu-Huai Fang and Shu-Yi Meng contributed equally to this paper.
(17)
Wang, L.; Xie, R. J.; Suehiro, T.; Takeda, T.; Hirosaki, N. DownConversion Nitride Materials for Solid State Lighting: Recent Advances and Perspectives. Chem. Rev. 2018, 118, 1951–2009. Xia, Z.; Liu, Q. Progress In Discovery And Structural Design Of Color Conversion Phosphors For LEDs. Prog. Mater Sci. 2016, 84, 59-117. Höppe, H. A. Recent Developments In The Field Of Inorganic Phosphors. Angew. Chem. Int. Ed. 2009, 48, 3572-3582. Pust, P.; Hintze, F.; Hecht, C.; Weiler, V.; Locher, A.; Zitnanska, D.; Harm, S.; Wiechert, D.; Schmidt, P. J.; Schnick, W. Group (III) Nitrides M[Mg2Al2N4](M= Ca, Sr, Ba, Eu) and Ba[Mg2Ga2N4] Structural Relation and Nontypical Luminescence Properties of Eu2+ Doped Samples. Chem. Mater. 2014, 26, 6113-6119. Schmiechen, S.; Schneider, H.; Wagatha, P.; Hecht, C.; Schmidt, P. J.; Schnick, W. Toward New Phosphors for Application in Illumination-Grade White Pc-LEDs: the Nitridomagnesosilicates Ca[Mg3SiN4]:Ce3+, Sr[Mg3SiN4]:Eu2+, and Eu[Mg3SiN4]. Chem. Mater. 2014, 26, 2712-2719. Pust, P.; Weiler, V.; Hecht, C.; Tücks, A.; Wochnik, A. S.; Henß, A.K.; Wiechert, D.; Scheu, C.; Schmidt, P. J.; Schnick, W. Narrow-band Red-emitting Sr[LiAl3N4]:Eu2+ as a Next-generation LED-phosphor Material. Nat. Mater. 2014, 13, 891-896. Strobel, P.; Schmiechen, S.; Siegert, M.; Tücks, A.; Schmidt, P. J.; Schnick, W. Narrow-band Green Emitting Nitridolithoalumosilicate Ba[Li2(Al2Si2)N6]:Eu2+with Framework Topology Whj for LED/LCD-Backlighting Applications. Chem. Mater. 2015, 27, 61096115. Tsai, Y. T.; Nguyen, H. D.; Lazarowska, A.; Mahlik, S.; Grinberg, M.; Liu, R. S. Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer. Angew. Chem. Int. Ed. 2016, 55, 9652-9656. Oh, J. H.; Eo, Y. J.; Yoon, H. C.; Huh, Y. D.; Do, Y. R. Evaluation of New Color Metrics: Guidelines for Developing Narrow-Band Red Phosphors for WLEDs. J. Mater. Chem. C 2016, 4, 8326-8348. Fang, M. H.; Tsai, Y. T.; Sheu, H. S.; Lee, J. F.; Liu, R. S. PressureControlled Synthesis of High-Performance SrLiAl3N4:Eu2+ NarrowBand Red Phosphors. J. Mater. Chem. C 2018, 6, 10174-10178. Watanabe, H.; Kijima, N. Synthesis of Sr0. 99Eu0. 01AlSiN3 from Intermetallic Precursor. J. Ceram. Soc. Jpn. 2009, 117, 115-119. Watanabe, T.; Nonaka, K.; Li, J.; Kishida, K.; Yoshimura, M. Low Temperature Ammonothermal Synthesis of Europium-Doped SrAlSiN3 for a Nitride Red Phosphor. J. Ceram. Soc. Jpn. 2012, 120, 500-502. Denton, A. R.; Ashcroft, N. W. Vegard’s law. Phys. Rev. A 1991, 43, 3161. Tessier, F.; Marchand, R. Ternary and higher order rare-earth nitride materials: synthesis and characterization of ionic-covalent oxynitride powders. J. Solid State Chem. 2003, 171, 143-151. Fang, M. H.; Wu, W. L.; Jin, Y.; Lesniewski, T.; Mahlik, S.; Grinberg, M.; Brik, M. G.; Srivastava, A. M.; Chiang, C. Y.; Zhou, W.; Jeong, D.; Kim, S. H.; Leniec, G.; Kaczmarek, S. M.; Sheu, H. S.; Liu, R. S. Control of Luminescence via Tuning of Crystal Symmetry and Local Structure in Mn4+-Activated Narrow Band Fluoride Phosphors. Angew. Chem. Int. Ed. 2018, 57, 1797-1801. Zhang, X.; Fang, M. H.; Tsai, Y.-T.; Lazarowska, A.; Mahlik, S.; Lesniewski, T.; Grinberg, M.; Pang, W. K.; Pan, F.; Liang, C.; Liu, R. S. Controlling of Structural Ordering and Rigidity of β-SiAlON:Eu through Chemical Cosubstitution to Approach Narrow-BandEmission for Light-Emitting Diodes Application. Chem. Mater. 2017, 29, 6781-6792. Takahashi, K.; Yoshimura, K. i.; Harada, M.; Tomomura, Y.; Takeda, T.; Xie, R. J.; Hirosaki, N. On the Origin of Fine Structure in the
ACS Paragon Plus Environment
4
Page 5 of 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Chemistry of Materials Photoluminescence Spectra of the β-SiAlON:Eu2+ Green Phosphor. Sci. Technol. Adv. Mater. 2012, 13, 015004. (18) Wu, Y. F.; Chan, Y. H.; Nien, Y. T.; Chen, I. G. Crystal Structure and Optical Performance of Al3+ and Ce3+ Codoped Ca3Sc2Si3O12 Green Phosphors for White LEDs. J. Am. Ceram. Soc. 2013, 96, 234-240. (19) Tsai, Y. T.; Chiang, C. Y.; Zhou, W.; Lee, J. F.; Sheu, H. S.; Liu, R. S. Structural Ordering and Charge Variation Induced by Cation Substitution in (Sr,Ca)AlSiN3:Eu Phosphor. J. Am. Chem. Soc. 2015, 137, 8936-8939. (20) Chen, Y.; Lim, P.; Lim, S.; Yang, Y.; Hu, L.; Chiang, H.; Tse, W. Raman Scattering Investigation of Yb:YAG Crystals Grown by the Czochralski Method. J. Raman Spectrosc. 2003, 34, 882-885.
“For Table of Contents Only”
ACS Paragon Plus Environment
5
