The analyses of structure and luminescence in (MgyY3-y) (Al5-ySiy)O12 and Y3(MgxAl5-2xSix)O12 ceramic phosphors

Journal of Alloys and Compounds 813 (2020) 152236

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The analyses of structure and luminescence in (MgyY3-y) (Al5-ySiy)O12 and Y3(MgxAl5-2xSix)O12 ceramic phosphors Yanna Tian a, b, Yanru Tang a, Xuezhuan Yi a, Gang Ao a, c, Jie Chen a, b, Deming Hao a, b, Yandan Lin d, *, Shengming Zhou a, ** a

Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, PR China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, PR China c Shanghai Tech University, Shanghai, 201210, PR China d School of Information Science and Technology Dept. Illumination Engineering & Light Sources Institute for Electric Light Sources, Fudan University, Shanghai, 200433, PR China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 20 June 2019 Received in revised form 24 August 2019 Accepted 10 September 2019 Available online 10 September 2019

In this paper, the chemical composition of Y3Al5O12 was modified to Ce:(MgyY2.99-y) (Al5-ySiy)O12 (MYASG) and Ce:Y2.99(MgxAl5-2xSix)O12 (YMASG) through the Mg2þ-Si4þ substitution for Y3þ-Al3þ and Al3þ-Al3þ, respectively. The increasing (decreasing) lattice constants, downward (upward) shift of Raman peaks and shorter (longer) luminescence lifetime were investigated in YMASG (MYASG) through the Rietveld analysis, Raman spectra and luminescent decay spectra. Moreover, a massive red-shift emission peak was observed in YMASG, from 537 nm to 577 nm. While for MYASG, the maximum emission peak of Ce3þ locates at 552 nm and the emission peaks remain unchanged even further increasing Mg2þ-Si4þ. The distinct red-shift properties can be ascribed to the different crystal structure due to the Mg2þ doping in different coordinate sites and are clarified by the configuration coordinate model. The broad color area from yellow to orange region in the color coordinates diagram was achieved which proves the great potential application of YMASG ceramic phosphors in the warm white light illumination. © 2019 Elsevier B.V. All rights reserved.

Keywords: YAG Ceramic phosphors Luminescence properties

1. Introduction In the past two decades, LEDs (light-emitting diodes) quickly developed and gradually replaced incandescent bulbs and fluorescent lamps in the lighting market [1e3]. At present, commercial white light-emitting diodes (WLEDs) are normally composed of InGaN chips and Ce:YAG yellow phosphors [4]. However, the thermal stability of such equipment is poor owing to the low thermal conductivity of the organic resin (<1 W/(m$K)) that phosphors are packed with [5]. Besides, the lack of red components in the luminescence spectrum of Ce:YAG yellow phosphors also limits its application in indoor and medical illumination for the high correlated color temperature (CCT) and the low colorrendering index (CRI). As a contrast, Ce:YAG ceramic phosphors have been broadly

* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (Y. Lin), [email protected] (S. Zhou). https://doi.org/10.1016/j.jallcom.2019.152236 0925-8388/© 2019 Elsevier B.V. All rights reserved.

studied for the application in WLEDs [6e9] because of its excellent mechanical, optical properties and high thermal conductivity [10]. The excellent thermal shock resistance of ceramic phosphors also makes it suitable for high power LED or high energy density LD excitation. In order to achieve Ce:YAG ceramic phosphors with low CCT and high CRI, some approaches to the increase of red component in its spectrum have been extensively investigated, such as codoping with Mn4þ, Cr3þ, Pr3þ etc. into YAG host, mixing CaAlSiN3:Eu2þ etc. phosphors with Ce:YAG phosphors and replacing Y3þ for Gd3þ, Tb3þ etc. in Ce:YAG [11e21]. In the recent years, the studies of Mg2þ-Si4þ co-doped Ce:YAG phosphors have attracted researchers’ attention again, since Robertson et al. first reported the substitution of Mg2þ-Si4þ pairs for Al3þ-Al3þ couple ions in YAG host [22]. Mengmeng Shang et al. indicated that a stronger crystal field splitting and red shift emissions of Ce3þ can be

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Fig. 1. XRD patterns of MYASG (a) and YMASG (b).

accomplished through the introduction of Mg2þ-Si4þ [23e30]. In fact, both Al3þ (CN ¼ 6) and Y3þ(CN ¼ 8) can be substituted by Mg2þ. However, the analyses of structure and luminescence properties in MYASG and YMASG are still unclear so far, to the best of our knowledge. In this work, MYASG and YMASG were designed with the same doping amounts of Mg2þ-Si4þ to better understand the effects of

Mg2þ doping in different coordinate sites on the crystal structure and luminescence properties. 2. Experimental The ceramic phosphors with nominal composition of Ce:(MgyY2.99-y) (Al5-ySiy)O12 (MYASG) (y ¼ 0.05,0.2,0.6 and 1, denoted by

Fig. 2. Rietveld refinements results of MYASG (a,b) and YMASG (c) (phase A is YAG and B is MgAl2O4); lattice constants of MYASG and YMASG ceramic phosphors (c).

Y. Tian et al. / Journal of Alloys and Compounds 813 (2020) 152236

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D-1, D-2, D-3 and D-4, respectively) and Ce:Y2.99(MgxAl5-2xSix)O12 (YMASG) (x ¼ 0,0.2,0.6 and 1, denoted by O-1, O-2, O-3 and O-4, respectively) were synthesized by solid-state reaction. The starting powders of high-purity Y2O3, Al2O3, CeO2, MgO and SiO2 were weighed and mixed with absolute ethyl alcohol milling for 24 h. The mixed powder was dried at 75  C for 24 h, then ground and sieved through a 200-mesh screen. The good dispersive powder was uniaxially pressed to plates at 25 Mpa and cold-pressed at 210 Mpa. The compact pellets were calcined in a muffle furnace at 700  C for 3 h, then sintered in vacuum at 1500e1650  C for 3 h. The obtained samples were annealed in air at 1400  C for 3 h to remove oxygen vacancies at last. The composition and crystal structure of samples were measured through X-ray diffraction (Empyrean, PANalytical, NED) using Cu Ka radiation in the rage of 2q ¼ 10-90 with 40 KV voltage and 40 mA electricity. The fracture microstructures of samples were characterized using scanning electron microscopy (S-4800, Hitachi, JPN). The wavelength conversion efficiency of samples was measured using an integrating sphere (ATA-500, Everfine, China) under a forward bias of 30 mA.The photoluminescence (PL), excitation (PLE) spectra and PL decay were measured using a highresolution spectrofluorometer (FLS 920, Edinburgh Instruments, UK). The Raman spectra were collected by a Renishaw inVia Raman microscope in the range of 100e900 cm1 using the 785 nm laser line for excitation. 3. Results and discussion 3.1. Phase identification and crystal structure Fig. 1 presents the XRD results of samples. For D-1, D-2, O-1 and O-2, the diffraction data match well with the standard data of Y3Al5O12 (PDF 33e0040), but a second phase of MgAl2O4 appears in D-3, D-4, O-3 and O-4. Apart from this, it is observed that all the diffraction peaks of (420) planes shift toward higher (lower) angles in MYASG (YMASG) samples, which implies the decrease (increase) of the lattice constants, as shown in Fig. 1a and b. The opposite shifting direction of (420) planes of MYASG and YMASG can be ascribed to the difference of ionic radius. For MYASG, the ionic radius of Si4þ (0.4 Å for CN ¼ 4) and Mg2þ (1.03 Å for CN ¼ 8) are smaller than Al3þ (0.53 Å for CN ¼ 4) and Y3þ (1.059 Å for CN ¼ 8). Therefore, when Y3þ-Al3þ couples are partly substituted by Mg2þ- Si4þ pairs, the diffraction peaks shift to bigger scattering. In contrary, for YMASG, the ionic radius of Mg2þ (0.86 Å for CN ¼ 6) is larger than Al3þ (0.675 Å for CN ¼ 6) and the influence of Mg2þ on the lattice constant is greater than that of Si4þ [1,5,22,31,32]. As a result, the diffraction peaks shift to smaller angle side with the increase of Mg2þ-Si4þ. To further explore the detailed structure and phase ratio of YAG and MgAl2O4 in MYASG and YMASG, the Rietveld refinements are implemented by the GSAS program using Y3Al5O12 and MgAl2O4 structure parameters as the initial model and the results are shown in Fig. 2, Table S1, and Fig. S1. As shown in the patterns, an increasing content of MgAl2O4 and a broad diffraction band between 16-36are observed in D-3, D-4, O-3 and O-4. The appearance of the broad diffraction band can attribute to the formation of MgAl2O4. The formation of MgAl2O4 phase will cause the precipitation of SiO2 with glass phase to keep the charge balance. Based on the appearance of those secondary phases, it is clear that the actual components of samples deviate from their nominal components (MYASG or YMASG). Nevertheless, it is shown in Fig. 2d that the lattice constants still decrease (increase) with the increase of Mg2þ-

Fig. 3. The fracture microstructures of MYASG samples (aed) and YMASG samples (eeh).

Si4þ in D-3 and D-4 (O-3 and O-4), which indicates the increasing amount of Y3þ-Al3þ (Al3þ-Al3þ) replaced by Mg2þ-Si4þ pairs. Besides, we calculated the data on the amount of Mg2þ doping according the results of Rietveld analysis, detail data as shown in Table S2. Therefore, the Mg2þ-Si4þ contents in actual components still increase with the increase of Mg2þ-Si4þ contents in nominal components regardless of the formation of MgAl2O4 and glass phase SiO2. Fig. 3 gives the fracture microstructures of samples. For D-1 and D-2 samples, the grain size is smaller than 10 mm and some pores are observed in grain boundary and interior. Whereas for D-3 and D-4 samples, it is notable that the grain boundaries are getting smoother with the emergence of a second phase. Combined with the discussion above, it is easy to understand that the smooth grain boundary can be attributed to the encapsulation of MYASG grains by the glass phase of SiO2, with the formation of MgAl2O4 second phase at the same time. For YMASG, the samples are densified without obvious pores and the grain size are uniform. Due to the content of second phase in O-3 and O-4 is less than D-3 and D-4, the smooth grain boundary is unobvious in O-3 and O-4. Fig. 4 provides the Raman spectra of MYASG and YMASG samples to explore the effect of different coordination site of Mg2þ on the crystal structure and chemical composition. In our experiment, 19 Raman modes were observed. For MYASG samples, the upward shift of the Raman peak located

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Fig. 4. Raman spectra of MYASG (a) and YMASG (b).

at 344 cm1 in the low-frequency range (100-380 cm1) is observed. Due to the Raman peaks in low-frequency region are mainly affected by the mass of ions [33e35], the upward-shift of Raman peaks can be ascribed to the substitution of Y3þ (89 u) by the lighter Mg2þ (24 u). In the medium-frequency range (380600 cm1), the positions of all bands barely change with the increase of Mg2þ-Si4þ concentration. In the high-frequency range (600-900 cm1), the shift of Raman peaks has no relative relationship with the mass of ions but is affected by the largeamplitude internal-mode motions of [AlO4] and [AlO6] moieties. The substitution of Mg2þ-Si4þ pairs for Y3þ-Al3þ couples will reduce the distance of (Al/Si)4eO and Al6eO, as shown in Fig. S1f. Therefore, the upward-shift of the Raman peak located at 853 cm1 can be ascribed to the increased distortion of [AlO4] and [AlO6] to accommodate for a decreasing unit-cell volume. For YMASG samples, it is found that the position of the band located at 345 cm1 shifts toward high frequency. As mentioned above, the upward-shift of the peak at 345 cm1 can be ascribed to the substitution of Al3þ (27 u) by the lighter Mg2þ (24 u). In the medium-frequency range, the positions of all bands barely change with increase of Mg2þ-Si4þ. In the high-frequency range, it is found that the positions of the bands located at 785 cm1 and 858 cm1 shift toward low frequency. Contrast to MYASG, the substitution of Mg2þ-Si4þ pairs for Al3þ-Al3þ couples will reduce the distance of (Al/Si)4eO and increase the distance of (Al/Mg)6eO, as shown in Fig. S1g and the downward-shift of these peaks can also be ascribed to the increased distortion of [AlO4] and [AlO6] to accommodate for an increasing unit-cell volume. Karlesson et al. pointed out that the upward-shift of highfrequency modes is correlated with higher structural rigidity [33].

In our work, the opposite shift of high-frequency modes indicates the higher structural rigidity of MYASG compared to YMASG. 3.2. Photoluminescence properties The PL and PLE spectra of samples measured at room temperature are shown in Fig. 5a and b. The emission band ranging from 480 to 730 nm under the 460 nm blue light excitation is ascribed to the 5d1/4f transition of Ce3þ, and the two excitation bands ranging from 300 to 380 nm and 390e520 nm monitored at 550 nm correspond to the 4f/5d2 and 4f/5d1 transitions of Ce3þ, respectively. Fig. 5c shows the emission peaks of MYASG and YMASG. For MYASG, the emission peaks shift from 540 nm to 552 nm and maintain 550 nm with the further increase of Mg2þSi4þ. For YMASG, the emission peaks gradually shift from 537 nm to 571 nm with the increase of Mg2þ-Si4þ. It is apparent that a more effective emission red-shift of Ce3þ can be achieved in YMASG than MYASG. In addition, we measured the PL spectra under the excitation of a 460 nm blue chip using an integrationg sphere to obtain the wavelegth conversion efficiency of samples [36e42]. The data on the wavelength conversion efficiency of Mg2þ doping were shown in Table S3. A thorough work about the red-shift mechanism of Ce3þ has been presented by Dorenbos et al. [43e45]. The redshift of Ce3þ is determined by the spectroscopic redshift D(A) and Stokes shift DS(A), as shown in Fig. 6a. Generally speaking, the electron excitation of Ce3þ from 4f to 5d1 energy level is accompanied by the adjustment of lattice equilibrium configuration, which is known as lattice relaxation. According to the PLE spectra of MYASG and YMASG, the all excitation peaks hardly change with the increase of

Y. Tian et al. / Journal of Alloys and Compounds 813 (2020) 152236

Fig. 5. PLE and PL spectra (lex ¼ 460 nm, lem ¼ 550 nm) of MYASG samples (a) and YMASG samples (b), the emission peaks of samples with the doping concentration of Mg2þ-Si4þ pairs (c).

Mg2þ-Si4þ. Therefore, it can be deduced that Stokes shift is the main reason for the emission red-shift of Ce3þ. As shown in Fig. 6b, c and d, the configuration coordination model is used to clarify the emission redshift caused by the Stokes shift. Generally, compounds containing more rigid chemical bonds tend to have a smaller Dr [46]. Combining the result of Raman spectra, i.e., the structural rigidity of MYASG is higher than YMASG, the configuration coordination model of 5d shifting to low energy and Dr decreasing (increasing) with the increase of Mg2þ-Si4þ in MYASG (YMASG) is

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proposed in Fig. 6c and d, in which E5d(r1)> E5d(r2)> E5d(r3)> E5d(r4), E4f(r1)> E4f(r2)> E4f(r3)> E4f(r4) in MYASG, and E5d(r5)> E5d(r6)> E5d(r7)> E5d(r8), E4f(r5)< E4f(r6)< E4f(r7)< E4f(r8) in YMASG. In MYASG, the difference of E5d(r1) and E4f(r1) is larger than that of E5d(r2) and E4f(r2), and the emission peak (540 nm) shifts to the longer wavelength (552 nm). While the difference of E5d(r2) and E4f(r2) is small than that of E5d(r3) and E4f(r3), so the emission peak (552 nm) shifts to the shorter wavelength (550 nm). Moreover, the difference of E5d(r3) and E4f(r3) is equal to that of E5d(r4) and E4f(r4), and the emission peak (550 nm) remains unchanged. In addition, the emission intensity of samples gradually decreases with the increase of Mg2þ-Si4þ, but the Raman spectra and configuration coordination model all prove that the MYASG should have better thermal stabilities34. Therefore, the decreasing emission intensity can be ascribed to the photoionization process from the 5d level to the conduction band with decreasing band gap when impurity ions are doped [47,48]. In YMASG, E5d(r5,6,7,8) gradually decrease and E4f(r5,6,7,8) gradually increase meaning the decreasing difference of E5d(ri) and E4f (ri) (i ¼ 5,6,7,8), so the emission peak shifts to longer wavelength. As for the decrease of emission intensity, it can be ascribed to the lowing cross point of 5d and 4f. The occurrence of nonradiative relaxation depend on the cross point, so the decrease of emission intensity can be ascribed to the increase of probability of nonradiative relaxation due to the lowing of cross point with the increase of Mg2þ-Si4þ. Fig. 7 presents the luminescence lifetime of MYASG and YMASG excited by 340 nm and monitored at 550 nm. The luminescence decay profiles are fitted with a single exponential function of IðtÞ ¼ I0 expð  t=tÞ, where I(t) and I0 is the luminescence intensity at time t and initial time, and t is the life time. For MYASG, the luminescence life time increases with the increase of Mg2þ-Si4þ can be ascribed to the suppression of nonradiative relaxation due to the increasing DE [49]. While, for YMASG, the luminescence life time becomes shorter with the increase of Mg2þ-Si4þ which can be ascribed to the increasing of nonradiative transition probability due to the decreasing DE. The Commission international l’Eclairage (CIE) color coordinates of YMASG are calculated to be (0.4212, 0.5552), (0.4397,0.5401), (0.4678, 0.5191) and (0.4954, 0.4959), respectively, in Fig. 8. With the increase of Mg2þ-Si4þ, the emission color of ceramic phosphors can be regulated from yellow-green to yellow-orange. The four lines in Fig. 8 denote color mixing solution of white light-emitting diodes composed with 460 InGaN chips and prepared ceramic phosphors, and the intersections of the color-mixing line with the Planckian locus indicated the CCT of lamp can be decreased from 10000 K to 3200 K. According to the calculation results by the CRI calculator [50], the higher CRI (Ra) value of 81 and lower CCT (4384 K) can be obtained by Ce:Y3Mg1Al3Si1O12 ceramic phosphors under the 460 nm blue light excitation, which confirms that the Mg2þ-Si4þ co-doped Ce:YAG transparent has a great potential in warm white light illumination. 4. Conclusions Ce:(MgyY2.99-y) (Al5-ySiy)O12 (MYASG) and Ce:Y2.99(MgxAl5(YMASG) ceramic phosphors have been fabricated through solid state reaction vacuum sintering to explore the different redshift properties of Ce:YAG with Mg2þ doped in dodecahedral and octahedral sites, respectively. With the increase of Mg2þ-Si4þ, great differences including the increasing (decreasing) lattice constants, upward (downward) shift of Raman

2xSix)O12

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Fig. 6. The energy level schemes of Ce3þ as free ion and in compounds A (a). D(A) is spectroscopic redshift determined by the centroid shift (εc (A)) and crystal field splitting (εcfs (A)); εc (A) is the shift of the average of the 5d configuration for Ce3þ in compound A; εcfs (A) is defined at the difference between the lowest energy and highest energy 5d level. The date is from Ref. [44]. and the configurational coordinate diagram of YAG (b), MYASG (c) and YMASG (d). DE is the activation energy associated with thermal quenching; DS is the Stokes shift; R0 is the ground equilibrium coordination; ri (i ¼ 1e8) is the excited equilibrium coordination of D-1, D-2, D-3, D-4, O-1, O-2, O-3, O-4 samples; Dr (Dr> 0)is the parabola offset between the ground and excited states; E5d (ri) and E4f(ri) (i ¼ 1e8) are the energy of 5d and 4f parabola corresponding to ri.

Fig. 7. Luminescence decay profiles of MYASG (a) and YMASG (b).

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Fig. 8. CIE Chromaticity coordinates of YMASG.

peaks at 100-380 cm1 and 600-900 cm1 and shorter (longer) lifetime in YMASG (MYASG). A more effective emission redshift of YMASG than MYASG was confirmed by PL spectra and the redshift mechanisms of both the MYASG and YMASG were discussed in details through configuration coordination models. When O-4 samples are combined with a 460 nm InGaN LED chip, a low CCT (4384 K) and a high CRI(Ra ¼ 81)values are achieved, which proves the great potential of YMASG in the application of “warm white” light illumination. The optimization work will focus on the effect of composite phase on improving the luminous efficacy in YMASG. Acknowledgements This work is supported by the International Partnership Program of Chinese Academy of Sciences, Grant No.181231KYSB20160005 and National Key R&D Program of China (Project No.2017YFB0403700). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jallcom.2019.152236. References [1] J.L. Wu, G. Gundiah, A.K. Cheetham, Structureeproperty correlations in Cedoped garnet phosphors for use in solid state lighting, Chem. Phys. Lett. 441 (2007) 250e254. [2] J. Cho, J.H. Park, J.K. Kim, E.F. Schubert, White Light-Emitting Diodes: History, Progress, and Future vol. 11, Laser & Photonics Reviews, 2017. [3] S. Pimputkar, J.S. Speck, S.P. DenBaars, S. Nakamura, Prospects for LED lighting, Nat. Photonics 3 (2009) 179e181. [4] E.F. Schubert, J.K. Kim, Solid-state light sources getting smart, Science 308 (2005) 1274e1278. [5] Q.P. Du, S.W. Feng, H.M. Qin, H. Hua, H. Ding, L. Jia, Z.J. Zhang, J. Jiang, H.C. Jiang, Massive red-shifting of Ce3þ emission by Mg2þ and Si4þ doping of YAG:Ce transparent ceramic phosphors, J. Mater. Chem. C 6 (2018) 12200e12205. [6] Y.R. Tang, S.M. Zhou, X.Z. Yi, H. Lin, S. Zhang, M. Hao de, Microstructure optimization of the composite phase ceramic phosphor for white LEDs with excellent luminous efficacy, Opt. Lett. 40 (2015) 5479e5481.

7

[7] S. Nishiura, S. Tanabe, K. Fujioka, Y. Fujimoto, M. Nakatsuka, Preparation and optical properties of transparent Ce:YAG ceramics for high power white LED, iumrs-ica 2008 symposium aa, Rare-Earth Related Material Processing and Functions 1 (2008). [8] E. Zych, C. Brecher, Temperature dependence of host-associated luminescence from YAG transparent ceramic material, J. Lumin. 90 (2000) 89e99. [9] Y. Yuan, D.Z. Wang, B.J. Zhou, S.W. Feng, M.Y. Sun, S. Zhang, W.N. Gao, Y. Bi, H.M. Qin, High luminous fluorescence generation using Ce:YAG transparent ceramic excited by blue laser diode, Opt. Mater. Express 8 (2018) 2760e2767. [10] K. Li, Y. Shi, F. Jia, C. Price, Y. Gong, J. Huang, N. Copner, H. Cao, L. Yang, S. Chen, H. Chen, J. Li, Low etendue yellow-green solid-state light generation by laserpumped LuAG:Ce ceramic, IEEE Photonics Technol. Lett. 30 (2018) 939e942. [11] D. Chen, Y. Zhou, W. Xu, J. Zhong, Z. Ji, W. Xiang, Enhanced luminescence of Mn4þ:Y3Al5O12 red phosphor via impurity doping, J. Mater. Chem. C 4 (2016) 1704e1712. [12] Z. Xia, Z. Xu, M. Chen, Q. Liu, Recent developments in the new inorganic solidstate LED phosphors, Dalton Trans. 45 (2016) 11214e11232. [13] Y.Q. Li, J.E.J. van Steen, J.W.H. van Krevel, G. Botty, A.C.A. Delsing, F.J. DiSalvo, G. de With, H.T. Hintzen, Luminescence properties of red-emitting M2Si5N8: Eu2þ (M¼Ca, Sr, Ba) LED conversion phosphors, J. Alloy. Comp. 417 (2006) 273e279. [14] C.-T. Chen, T.-J. Lin, M.S. Molokeev, W.-R. Liu, Synthesis, luminescent properties and theoretical calculations of novel orange-red-emitting Ca 2 Y 8 (SiO 4 ) 6 O 2 :Sm 3þ phosphors for white light-emitting diodes, Dyes Pigments 150 (2018) 121e129. [15] B. Han, Y. Dai, J. Zhang, X. Wang, W. Shi, H. Shi, NaLaMgWO 6 :Pr 3þ : a novel blue-light excitable red-emitting phosphor for white light-emitting diodes, J. Lumin. 196 (2018) 275e280. [16] T. Zorenko, V. Gorbenko, S. Witkiewicz-Lukaszek, Y. Zorenko, Luminescent properties of (La,Lu,Gd)3(Al,Sc,Ga)5O12:Ce mixed garnets under synchrotron radiation excitation, J. Lumin. 199 (2018) 483e487. [17] S. Li, Q. Zhu, L. Wang, D. Tang, Y. Cho, X. Liu, N. Hirosaki, T. Nishimura, T. Sekiguchi, Z. Huang, R.-J. Xie, CaAlSiN3:Eu2þ translucent ceramic: a promising robust and efficient red color converter for solid state laser displays and lighting, J. Mater. Chem. C 4 (2016) 8197e8205. [18] B. Wang, H. Lin, J. Xu, H. Chen, Y. Wang, CaMg(2)Al(1)(6)O(2)(7):Mn(4)(þ)based red phosphor: a potential color converter for high-powered warm WLED, ACS Appl. Mater. Interfaces 6 (2014) 22905e22913. [19] J. Chen, Z. Deng, Z. Liu, Y. Lin, H. Lan, D. Chen, B. Fei, C. Wang, F. Wang, Q. Hu, Y. Cao, Optical enhancement brought by doping Gd(3þ) ions into Ce: YAG ceramics for indoor white light-emitting diodes, Opt. Express 23 (2015) A292eA298. [20] Y.R. Tang, S.M. Zhou, X.Z. Yi, D.M. Hao, X.C. Shao, J. Chen, The characterization of Ce/Pr-doped YAG phosphor ceramic for the white LEDs, J. Alloy. Comp. 745 (2018) 84e89. [21] Y.R. Tang, S.M. Zhou, X.Z. Yi, S. Zhang, D.M. Hao, X.C. Shao, The Cr-doping effect on white light emitting properties of Ce:YAG phosphor ceramics, J. Am. Ceram. Soc. 100 (2017) 2590e2595. [22] J.M. Robertson, M.W. Vantol, W.H. Smits, J.P.H. Heynen, Colorshift of the CE3þ emission in mono-crystalline epitaxially grown garnet layers, Philips J. Res. 36 (1981) 15e30. [23] C. He, H.P. Ji, Z.H. Huang, T.S. Wang, X.G. Zhang, Y.G. Liu, M.H. Fang, X.W. Wu, J.Q. Zhang, X. Min, Red-shifted emission in Y3MgSiAl3O12:Ce3þ garnet phosphor for blue light-pumped white light-emitting diodes, J. Phys. Chem. C 122 (2018) 15659e15665. [24] Q. Du, S. Feng, H. Qin, H. Hua, H. Ding, L. Jia, Z. Zhang, J. Jiang, H. Jiang, Massive red-shifting of Ce3þ emission by Mg2þ and Si4þ doping of YAG:Ce transparent ceramic phosphors, J. Mater. Chem. C 6 (2018) 12200e12205. [25] J.B. Song, K.X. Song, J.S. Wei, H.X. Lin, J. Wu, J.M. Xu, W.T. Su, Z.Q. Cheng, Ionic occupation, structures, and microwave dielectric properties of Y3MgAl3SiO12 garnet-type ceramics, J. Am. Ceram. Soc. 101 (2018) 244e251. [26] Y.J. Zheng, H.M. Zhang, H.R. Zhang, Z.G. Xia, Y.L. Liu, M.S. Molokeev, B.F. Lei, Co-substitution in Ca1-xYxAl12-xMgxO19 phosphors: local structure evolution, photoluminescence tuning and application for plant growth LEDs, J. Mater. Chem. C 6 (2018) 4217e4224. [27] M.C. Maniquiz, K.Y. Jung, S.M. Jeong, Luminescence characteristics of Y[sub 3] Al[sub 52y](Mg,Si)[sub y]O[sub 12]:Ce phosphor prepared by spray pyrolysis, J. Electrochem. Soc. 157 (2010). [28] M.C. Maniquiz, K.Y. Jung, S.M. Jeong, Luminescence comparison and enhancement of Ce-doped yttrium aluminum garnet phosphor via cation substitution and adding flux, J. Electrochem. Soc. 158 (2011). [29] Z.F. Pan, J.C. Chen, H.Q. Wu, W.Q. Li, Red emission enhancement in Ce3þ/ Mn2þ co-doping suited garnet host MgY2Al4SiO12 for tunable warm white LED, Opt. Mater. 72 (2017) 257e264. [30] Z.F. Pan, R.P. Wang, W.Q. Li, H.Q. Wu, J.C. Chen, Y.F. Zheng, Cooperative cation substitution facilitated construction of garnet oxynitride MgY2Al3Si2O11N: Ce3þ for white LEDs, J. Am. Ceram. Soc. 101 (2018) 5451e5460. [31] M. Shang, J. Fan, H. Lian, Y. Zhang, D. Geng, J. Lin, A double substitution of Mg2þ-Si4þ/Ge4þ for Al(1)(3þ)-Al(2)3þ in Ce3þ-doped garnet phosphor for white LEDs, Inorg. Chem. 53 (2014) 7748e7755. [32] H. Lin, J. Xu, Q. Huang, B. Wang, H. Chen, Z. Lin, Y. Wang, Bandgap tailoring via Si doping in inverse-garnet Mg3Y2Ge3O12:Ce(3þ) persistent phosphor potentially applicable in AC-LED, ACS Appl. Mater. Interfaces 7 (2015) 21835e21843. [33] Y.C. Lin, P. Erhart, M. Bettinelli, N.C. George, S.F. Parker, M. Karlsson,

8

[34]

[35]

[36]

[37]

[38]

[39]

[40]

[41]

[42]

Y. Tian et al. / Journal of Alloys and Compounds 813 (2020) 152236 Understanding the interactions between vibrational modes and excited state relaxation in Y3-xCexAl5O12: design principles for phosphors based on 5d-4f transitions, Chem. Mater. 30 (2018) 1865e1877. Y.N. Zhou, W.D. Zhuang, Y.S. Hu, R.H. Liu, H.B. Xu, M.Y. Chen, Y.H. Liu, Y.F. Li, Y.L. Zheng, G.T. Chen, Cyan-green phosphor (Lu2M)(Al4Si)O-12:Ce3þ for high -quality LED lamp: tunable photoluminescence properties and enhanced thermal stability, Inorg. Chem. 58 (2019) 1492e1500. K. Papagelis, G. Kanellis, S. Ves, G.A. Kourouklis, Lattice dynamical properties of the rare earth aluminum garnets (RE3Al5O12), Phys. Status Solidi B-Basic Solid State Phys. 233 (2002) 134e150. A.P. Jadhav, A. Pawar, U. Pal, B.K. Kim, Y.S. Kang, Synthesis of monodispersed red emitting LiAl5O8:Fe3þ nanophosphors, Sci. Adv. Mater. 4 (2012) 597e603. A.P. Jadhav, A. Pawar, T.R. Hwang, J.W. Lee, M.W. Choi, B.K. Kim, Y.S. Kang, Wavelength conversion using rare earth doped oxides in polyolefin based nanocomposite films, Polym. Int. 61 (2012) 943e950. A.P. Jadhav, A.U. Pawar, U. Pal, Y.S. Kang, Red emitting Y2O3:Eu3þ nanophosphors with > 80% down conversion efficiency, J. Mater. Chem. C 2 (2014) 496e500. A.U. Pawar, A.P. Jadhav, U. Pal, B.K. Kim, Y.S. Kang, Blue and red dual emission nanophosphor CaMgSi2O6:Eunþ; crystal structure and electronic configuration, J. Lumin. 132 (2012) 659e664. A. Pawar, A. Jadhav, C.W. Kim, H.G. Cha, U. Pal, Y.S. Kang, Emission controlled dual emitting Eu-doped CaMgSi2O6 nanophosphors, J. Lumin. 157 (2015) 131e136. C.W. Kim, W.J. Shin, M.J. Choi, J.H. Lee, S.H. Nam, Y.D. Suh, Y.S. Kang, Y.S. Kang, Wavelength conversion effect-assisted dye-sensitized solar cells for enhanced solar light harvesting, J. Mater. Chem. 4 (2016) 11908e11915. M.J. Kang, E.G. Santoro, Y.S. Kang, Enhanced efficiency of functional smart window with solar wavelength conversion phosphor-photochromic hybrid

film, ACS Omega 3 (2018) 9505e9512. [43] P. Dorenbos, Optical basicity, interpreted by means of Ce3þ 5d level spectroscopy in ionic crystals, J. Non-Cryst. Solids 324 (2003) 220e229. [44] E. van der Kolk, P. Dorenbos, A.P. Vink, R.C. Perego, C.W.E. van Eijk, A.R. Lakshmanan, Vacuum ultraviolet excitation and emission properties of Pr3þ and Ce3þ in MSO4 (M¼Ba, Sr, and Ca) and predicting quantum splitting by Pr3þ in oxides and fluorides, Phys. Rev. B 64 (2001) 12. [45] X. Qin, X.W. Liu, W. Huang, M. Bettinelli, X.G. Liu, Lanthanide-activated phosphors based on 4f-5d optical transitions: theoretical and experimental aspects, Chem. Rev. 117 (2017) 4488e4527. [46] A.A. Setlur, J.J. Shiang, M.E. Hannah, U. Happek, Phosphor quenching in LED packages: measurements, mechanisms, and paths forward, in: Proceedings of the SPIE - the International Society for Optical Engineering, SPIE - The International Society for Optical Engineering, 2009, 74220E (74228 pp.)-74220E (74228 pp.). [47] Y. Wang, J. Ding, Y. Wang, Ca2-xY1þxZr2-xAl3þxO12:Ce3þ: solid solution design toward the green emission garnet structure phosphor for near-UV LEDs and their luminescence properties, J. Phys. Chem. C 121 (2017) 27018e27028. [48] J. Ueda, S. Tanabe, T. Nakanishi, Analysis of Ce luminescence quenching in solid solutions between Y(3)Al(5)O(12) and Y(3)Ga(5)O(12) by temperature dependence of photoconductivity measurement, J. Appl. Phys. 110 (2011), 53102-531026. [49] S.X. Li, L. Wang, Q.Q. Zhu, D.M. Tang, X.J. Liu, G.F. Cheng, L. Lu, T. Takeda, N. Hirosaki, Z.R. Huang, R.J. Xie, Crystal structure, tunable emission and applications of Ca1-xAl1-xSi1þxN3-xOx :RE (x¼0-0.22, RE ¼ Ce3þ, Eu2þ) solid solution phosphors for white light-emitting diodes, J. Mater. Chem. C 4 (2016) 11219e11230. [50] K. Smet, J. Schanda, L. Whitehead, M. Luo, CRI2012 calculator, in, 2015.