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Effect of annealing in hydrogen atmosphere on the photoluminescence properties of phosphor-in- glass in tellurate glass
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol
Effect of annealing in hydrogen atmosphere on the photoluminescence properties of phosphor-in- glass in tellurate glass Heyu Zhoua, Jun Zoua,⁎, Yang Lia, Wenjuan Wua,⁎, Mingming Shib, Bobo Yangb, Ziming Wanga a b
School of Material Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China School of Science, Shanghai Institute of Technology, Shanghai 201418, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords: Hydrogen annealing Phosphor-in-glass Sintering temperature Photoluminescence Tellurate glass
A series of phosphor-in-glasses (PIGs) was prepared by one-step melt-quenching method sintering the mixture of tellurate raw material powder and YAG:Ce3 + phosphors at 450–700 °C, of which some was annealed at 250 °C for 3 h under the hydrogen atmosphere. The test results show that the relative photoluminescence (PL) intensity of phosphor-in-glass sintered at 450–700 °C was significantly strengthened from 42.29% to 174.72% after the hydrogen annealing, and the relative photoluminescence excitation (PLE) intensity from 21.00% to 207.90%. However, the relative photoluminescence intensity of the PIG sintered at 700 °C before and after hydrogen annealing was nearly zero because of the destruction of crystal structural surrounding Ce3 + ion. The concentration of Ce3 + and Ce4 + measured by X-ray photoelectron spectrum analyser (XPS) in PIGs before and after hydrogen annealing obviously happened to change, which was associated with the variation of PL and PL excitation intensity. Besides, the X-ray diffraction (XRD) pattern of YAG:Ce3 + phosphor and PIGs sintered at different temperatures further presented the destruction of YAG:Ce3 + lattice as the sintering temperature increased. Therefore, the appropriate sintering temperature and hydrogen annealing can increase the PL and PLE intensity and the Ce3 + concentration.
1. Introduction White light-emitting diodes (WLEDs), the new generation of solidstate lighting source, have been extensively used in display backlighting, automotive headlamps, street lamps, and interior lighting because of the features of long lifetime, high luminous efficiency, energy saving, environment-friendly and so on [1,2]. The current commercial WLED is obtained by combining a gallium nitride (GaN) based blue chip with yellow phosphor (yellow YAG: Ce3 + phosphor), which was packaged by organic encapsulants, such as resin or silicone [3,4,5]. Nevertheless, resin and silicone encapsulation are colored by the heat from the blue GaN chip and easily aging after long-term service, ascribing to poor thermal conductivity and thermal stability, which may reduce the secular reliability of the WLED [6,7,8]. Therefore, inorganic materials with excellent thermal conductivity and thermal stability, such as phosphor-ceramics and phosphor-in-glasses (PIGs), are the pretty good choice to replace polymer sealant as potential phosphor carrier applied in light-emitting diodes encapsulation [9,10,11]. Compared with phosphor-ceramics, the luminescence of PIG can be easily controlled through incorporating of different phosphors into glass composition and the low-temperature synthesis of PIG (< 800 °C) can
⁎
keep the high performance of doped phosphor in the course of the fabrication process, Consequently, PIG has attracted more attention than phosphor-ceramics [9]. YAG:Ce3 + PIG, manufactured by co-sintering of the uniform mixture of commercial YAG:Ce3 + phosphors and glass raw material powders at a suitable temperature [12], shows yellow emission because of the Ce3 +: 5d → 4f transition by 460 nm excitation [13]. The efficient luminescence of YAG: Ce3 + PIG can be achieved by decreasing the corrosion of melting glass to phosphor and matching the refraction index between glass matrix and phosphor to keep PIG transparent and reduce light scattering [11]. Meanwhile, the luminescent properties of the YAG: Ce3 + PIG can be also significantly enhanced by controlling the reducing atmosphere diminishing the oxidation of Ce3 + of the PIG [6]. Recently, tellurate glasses are considered as the attractive glass matrix to prepared the phosphor-in-glass due to the low melting temperature and high refraction index [14,15]. In this paper, TeO2-based PIGs, prepared by varying the sintering temperature from 450 °C to 700 °C, were annealed at 250 °C for 3 h in the condition of hydrogen atmosphere. The photoluminescence (PL) and photoluminescence excitation (PLE) of the PIGs before annealing were compared with those after annealing. In addition, the XRD and
Corresponding author. E-mail address: [email protected] (J. Zou).
http://dx.doi.org/10.1016/j.jnoncrysol.2017.09.019 Received 27 March 2017; Received in revised form 22 August 2017; Accepted 5 September 2017 0022-3093/ © 2017 Elsevier B.V. All rights reserved.
Please cite this article as: Zhou, H., Journal of Non-Crystalline Solids (2017), http://dx.doi.org/10.1016/j.jnoncrysol.2017.09.019
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
H. Zhou et al.
Fig. 1. PLE and PL of the PIGs sintered at different temperature: (a) PLE spectra before annealing; (b) PL spectra before annealing; (c) PLE spectra after annealing; (d) PL spectra after annealing.
Fig. 2. Increasing ratio of spectral peak intensity of the PIGs sintering at different temperature after annealing: (a) increasing ratio of PLE spectra peak intensity; (b) increasing ratio of PL spectral peak intensity.
XPS were carried out to analyses the crystal structure and the Ce3 + concentration in the samples.
temperature between 450 °C and 700 °C for 0.5 h by one-step meltquenching method [16], and the glass melt was fleetly poured into a cold copper mould, which gradually cooled to room temperature. Part of the produced were cut and polished into plates with 1 mm thickness was annealed at 250 °C for 3 h under the mixture atmosphere of H2 and N2 (5%H2, 95%N2). The photoluminescence (PL) and PL excitation (PLE) spectra were
2. Experiments The uniform mixture of 70%TeO2-20%ZnO-10%Na2O (mol%) -based glass raw materials and 7% YAG phosphor was sintered at the 2
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
H. Zhou et al.
Fig. 3. XPS spectra and curve-fittings of Ce3d in the PIGs sintered at 600 °C and 700 °C before and after hydrogen annealing: (a) PIG sintered at 600 °C before annealing; (b) PIG sintered at 700 °C before annealing; (c) PIG sintered at 600 °C after annealing; (d) PIG sintered at 700 °C after annealing.
measured by the Edinburgh Instrument spectrofluorometer (FLS920) equipped with a xenon lamp at room temperature. The crystalline phases of samples were examined using the X-ray diffraction (XRD; Rigaku, Ultima IV, Japan) controlled at a scanning rate of 0.02°/step and 4°/min with Cu Ka radiation (k = 0.154178 nm) in the range of 10–70°2θ. The concentration of Ce3 + and Ce4 + were calculated by an X-ray photoelectron spectrum analyser (Escalab 250Xi, ThermoFisher) and the minimum resolution of the apparatus was 0.1 eV. The hydrogen annealing was carried out by the KTL1400 tube furnace with a 60 ml/ min of H2 flow rate.
Table 1 Relative percentage of Ce3 + in PIG sintered at 600 °C before annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.594 898.841 888.665 5983.760
4.44 7.81 5.94 6.17
1199.961 13,267.006 9120.798 5983.760
14,466.967
48.9
15,104.558
51.1
3. Results and discussion Table 2 Relative percentage of Ce3 + in PIG sintered at 700 °C before annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
885.804 899.882 889.162 904.071
5.37 9.09 5.34 4.17
3324.110 18,038.183 6779.523 1487.229
21,362.293
72.1
8266.752
27.9
Fig. 1a–d shows the PLE and PL spectra of PIGs obtained at different sintering temperature before and after annealing. The PLE and PL intensities of before and after hydrogen annealing increased as the sintering temperature increased up to 600 °C, and decreased with the increment of sintering temperature over 600 °C. Moreover, when the sintering temperature was 700 °C, the value of all excitation and emission peaks was nearly zero, which was due the interaction between the glass melt and YAG phosphor particles under the excessive sintering temperature. Compared with the before hydrogen annealing, the PLE and PL intensity of the PIGs sintered at different temperature other than 700 °C were all enhanced after hydrogen annealing. Hence, the hydrogen annealing was an excellent measure to strengthen the PL intensity of PIGs, but the excessive sintering temperature was not beneficial to improve the PL intensity of the PIG. Fig. 2a–b exhibits the relationship between increasing ratio of the peak intensity and the different sintering temperature. Fig. 2a reveals that the enhancement percentage of the PLE spectral peak intensity was improved from 21.00% to 207.90% as the sintering temperature varied after hydrogen annealing, and Fig. 2b displays that the enhancement increasing ratio of the PL spectral peak intensity was raised from
Table 3 Relative percentage of Ce3 + in PIG sintered at 600 °C after annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.672 897.629 888.702 902.372
4.44 6.62 6.12 7.04
1256.826 8060.738 9242.096 11,057.264
9317.564
31.4
20,299.36
68.6
3
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
H. Zhou et al.
Table 4 Relative percentage of Ce3 + in PIG sintered at 700 °C after annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.062 899.142 888.142 903.760
3.49 7.98 6.33 5.84
615.844 14,373.751 9778.275 4783.934
14,989.595
50.7
14,562.209
49.3
Fig. 4. XRD patterns of YAG: Ce3 + phosphor and PIGs under different sintering temperatures: (a) XRD of YAG: Ce3 + phosphor; (b) XRD of PIGs.
excitation and emission peak intensity. Hence, test results indicated that high sintering temperature can also destroy the photoluminescence properties of PIG.
42.29% to 174.72% with the variation of the sintering temperature after hydrogen annealing. However, the PLE and PL intensity of PIG sintered at 700 °C was not enhanced after hydrogen annealing. The 884, 902, 881.6, and 899.9 eV binding energies correspond orderly to the Ce3 + 3d5/2, Ce3 + 3d3/2, Ce4 + 3d5/2, and Ce4 + 3d3/2 components from the standard database of XPS spectra [17,18]. Fig. 3 illustrates the XPS spectra and fitting curve of the Ce3d in PIG sintered at 600 °C and 700 °C before and after annealing. All the spectra fitting dates are listed in the Tables 1–4, including maximum binding energy, FWHM, peak area, and the relative content of Ce3 + (the ratio of peak area [Ce3 +] / peak area [Ce3 + + Ce4 +]). The test results based on the tables explained that the Ce3 + concentration of PIG decreased as the sintering temperature increased, which was ascribed to the oxidation of Ce3 +. As shown in Tables 1–2, the relative percentage of Ce3 + dispersed in PIG decreased from 51.1% to 27.9% before hydrogen annealing. The change may account for the reason why the high sintering temperature results in worse luminescence properties (Fig. 1). Only one electron in the 4f layer of Ce3 + can transit to 5d layer to produce luminescence considering the luminescence principle of YAG: Ce3 + [19,20]. When the Ce3 + ion is oxidized to Ce4 +, the excitation and emission from 4f to 5d are not realized because of no remaining electrons in the 4f layer. With respect to Table 1, the Ce3 + concentration of Table 3 increased from 51.1% to 68.6% after hydrogen annealing, mainly due to the annealing of the Ce4 + in PIGs. Consequently, the low sintering temperature and hydrogen annealing are beneficial to enhance the luminescence properties and the Ce3 + concentration of the PIGs. Fig. 4 shows the XRD pattern of YAG: Ce3 + phosphor and PIGs obtained at different sintering temperature. The pattern of Fig. 4a indicated that the diffraction peaks of YAG and the standard card (PDF#33-0040) were matched with the sintering temperature increasing [21], but obvious change in the diffraction peaks of PIG can be observed from Fig. 4b. When the sintering temperature was 700 °C, the diffraction peaks of PIG entirely disappeared because of the destruction of the lattice structure of YAG, which can lead to the decrease of the
4. Conclusion In this paper, the PIGs have been successfully prepared by the onestep melt-quenching method. The effect of hydrogen annealing on the PIGs sintered at 450–700 °C was discussed and analyzed by PL spectra, XPS and XRD. The PLE peak intensity of the PIG sintered below 700 °C was enhanced from 21.00% to 207.90% and the PL of the PIG from 42.29% to 174.72% after hydrogen annealing, which can be ascribed to the increasement of Ce3 + concentration after reducing. However, the excitation and emission spectra of PIG sintered at 700 °C entirely disappeared because of the destruction of the crystal structure around the Ce3 + ions. Hence, the hydrogen annealing and the appropriate sintering temperature can the PL and PLE intensity and the Ce3 + ion concentration. Acknowledgements This work was supported by National Nature Science Foundation of China (51302171), Science and Technology Commission of Shanghai Municipality (14500503300), Shanghai Cooperative Project (shanghaiCXY2013-61). References [1] Peng Yang, Ruixin Li, Hao Cheng, Zhen Chen, Hong Li, Mingxiang Chen, Facile preparation of patterned phosphor-in-glass with excellent luminous properties through screen-printing for high-power white light-emitting diodes, J. Alloys Compd. 693 (2017) 279–284, http://dx.doi.org/10.1016/j.jallcom.2016.09.197. [2] Daqin Chen, Weidong Xiang, Xiaojuan Liang, Jiasong Zhong, Hua Yu, Mingye Ding, Hongwei Lu, Zhenguo Ji, Advances in transparent glass–ceramic phosphors for white light-emitting diodes—a review, J. Eur. Ceram. Soc. 35 (2015) 859–869, http://dx.doi.org/10.1016/j.jeurceramsoc.2014.10.002. [3] Hoyong Yie, Sunil Kim, Yurian Kim, Hyungsun Kim, Modifying optical properties of
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Contents lists available at ScienceDirect
Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol
Effect of annealing in hydrogen atmosphere on the photoluminescence properties of phosphor-in- glass in tellurate glass Heyu Zhoua, Jun Zoua,⁎, Yang Lia, Wenjuan Wua,⁎, Mingming Shib, Bobo Yangb, Ziming Wanga a b
School of Material Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, PR China School of Science, Shanghai Institute of Technology, Shanghai 201418, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords: Hydrogen annealing Phosphor-in-glass Sintering temperature Photoluminescence Tellurate glass
A series of phosphor-in-glasses (PIGs) was prepared by one-step melt-quenching method sintering the mixture of tellurate raw material powder and YAG:Ce3 + phosphors at 450–700 °C, of which some was annealed at 250 °C for 3 h under the hydrogen atmosphere. The test results show that the relative photoluminescence (PL) intensity of phosphor-in-glass sintered at 450–700 °C was significantly strengthened from 42.29% to 174.72% after the hydrogen annealing, and the relative photoluminescence excitation (PLE) intensity from 21.00% to 207.90%. However, the relative photoluminescence intensity of the PIG sintered at 700 °C before and after hydrogen annealing was nearly zero because of the destruction of crystal structural surrounding Ce3 + ion. The concentration of Ce3 + and Ce4 + measured by X-ray photoelectron spectrum analyser (XPS) in PIGs before and after hydrogen annealing obviously happened to change, which was associated with the variation of PL and PL excitation intensity. Besides, the X-ray diffraction (XRD) pattern of YAG:Ce3 + phosphor and PIGs sintered at different temperatures further presented the destruction of YAG:Ce3 + lattice as the sintering temperature increased. Therefore, the appropriate sintering temperature and hydrogen annealing can increase the PL and PLE intensity and the Ce3 + concentration.
1. Introduction White light-emitting diodes (WLEDs), the new generation of solidstate lighting source, have been extensively used in display backlighting, automotive headlamps, street lamps, and interior lighting because of the features of long lifetime, high luminous efficiency, energy saving, environment-friendly and so on [1,2]. The current commercial WLED is obtained by combining a gallium nitride (GaN) based blue chip with yellow phosphor (yellow YAG: Ce3 + phosphor), which was packaged by organic encapsulants, such as resin or silicone [3,4,5]. Nevertheless, resin and silicone encapsulation are colored by the heat from the blue GaN chip and easily aging after long-term service, ascribing to poor thermal conductivity and thermal stability, which may reduce the secular reliability of the WLED [6,7,8]. Therefore, inorganic materials with excellent thermal conductivity and thermal stability, such as phosphor-ceramics and phosphor-in-glasses (PIGs), are the pretty good choice to replace polymer sealant as potential phosphor carrier applied in light-emitting diodes encapsulation [9,10,11]. Compared with phosphor-ceramics, the luminescence of PIG can be easily controlled through incorporating of different phosphors into glass composition and the low-temperature synthesis of PIG (< 800 °C) can
⁎
keep the high performance of doped phosphor in the course of the fabrication process, Consequently, PIG has attracted more attention than phosphor-ceramics [9]. YAG:Ce3 + PIG, manufactured by co-sintering of the uniform mixture of commercial YAG:Ce3 + phosphors and glass raw material powders at a suitable temperature [12], shows yellow emission because of the Ce3 +: 5d → 4f transition by 460 nm excitation [13]. The efficient luminescence of YAG: Ce3 + PIG can be achieved by decreasing the corrosion of melting glass to phosphor and matching the refraction index between glass matrix and phosphor to keep PIG transparent and reduce light scattering [11]. Meanwhile, the luminescent properties of the YAG: Ce3 + PIG can be also significantly enhanced by controlling the reducing atmosphere diminishing the oxidation of Ce3 + of the PIG [6]. Recently, tellurate glasses are considered as the attractive glass matrix to prepared the phosphor-in-glass due to the low melting temperature and high refraction index [14,15]. In this paper, TeO2-based PIGs, prepared by varying the sintering temperature from 450 °C to 700 °C, were annealed at 250 °C for 3 h in the condition of hydrogen atmosphere. The photoluminescence (PL) and photoluminescence excitation (PLE) of the PIGs before annealing were compared with those after annealing. In addition, the XRD and
Corresponding author. E-mail address: [email protected] (J. Zou).
http://dx.doi.org/10.1016/j.jnoncrysol.2017.09.019 Received 27 March 2017; Received in revised form 22 August 2017; Accepted 5 September 2017 0022-3093/ © 2017 Elsevier B.V. All rights reserved.
Please cite this article as: Zhou, H., Journal of Non-Crystalline Solids (2017), http://dx.doi.org/10.1016/j.jnoncrysol.2017.09.019
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
H. Zhou et al.
Fig. 1. PLE and PL of the PIGs sintered at different temperature: (a) PLE spectra before annealing; (b) PL spectra before annealing; (c) PLE spectra after annealing; (d) PL spectra after annealing.
Fig. 2. Increasing ratio of spectral peak intensity of the PIGs sintering at different temperature after annealing: (a) increasing ratio of PLE spectra peak intensity; (b) increasing ratio of PL spectral peak intensity.
XPS were carried out to analyses the crystal structure and the Ce3 + concentration in the samples.
temperature between 450 °C and 700 °C for 0.5 h by one-step meltquenching method [16], and the glass melt was fleetly poured into a cold copper mould, which gradually cooled to room temperature. Part of the produced were cut and polished into plates with 1 mm thickness was annealed at 250 °C for 3 h under the mixture atmosphere of H2 and N2 (5%H2, 95%N2). The photoluminescence (PL) and PL excitation (PLE) spectra were
2. Experiments The uniform mixture of 70%TeO2-20%ZnO-10%Na2O (mol%) -based glass raw materials and 7% YAG phosphor was sintered at the 2
Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx
H. Zhou et al.
Fig. 3. XPS spectra and curve-fittings of Ce3d in the PIGs sintered at 600 °C and 700 °C before and after hydrogen annealing: (a) PIG sintered at 600 °C before annealing; (b) PIG sintered at 700 °C before annealing; (c) PIG sintered at 600 °C after annealing; (d) PIG sintered at 700 °C after annealing.
measured by the Edinburgh Instrument spectrofluorometer (FLS920) equipped with a xenon lamp at room temperature. The crystalline phases of samples were examined using the X-ray diffraction (XRD; Rigaku, Ultima IV, Japan) controlled at a scanning rate of 0.02°/step and 4°/min with Cu Ka radiation (k = 0.154178 nm) in the range of 10–70°2θ. The concentration of Ce3 + and Ce4 + were calculated by an X-ray photoelectron spectrum analyser (Escalab 250Xi, ThermoFisher) and the minimum resolution of the apparatus was 0.1 eV. The hydrogen annealing was carried out by the KTL1400 tube furnace with a 60 ml/ min of H2 flow rate.
Table 1 Relative percentage of Ce3 + in PIG sintered at 600 °C before annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.594 898.841 888.665 5983.760
4.44 7.81 5.94 6.17
1199.961 13,267.006 9120.798 5983.760
14,466.967
48.9
15,104.558
51.1
3. Results and discussion Table 2 Relative percentage of Ce3 + in PIG sintered at 700 °C before annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
885.804 899.882 889.162 904.071
5.37 9.09 5.34 4.17
3324.110 18,038.183 6779.523 1487.229
21,362.293
72.1
8266.752
27.9
Fig. 1a–d shows the PLE and PL spectra of PIGs obtained at different sintering temperature before and after annealing. The PLE and PL intensities of before and after hydrogen annealing increased as the sintering temperature increased up to 600 °C, and decreased with the increment of sintering temperature over 600 °C. Moreover, when the sintering temperature was 700 °C, the value of all excitation and emission peaks was nearly zero, which was due the interaction between the glass melt and YAG phosphor particles under the excessive sintering temperature. Compared with the before hydrogen annealing, the PLE and PL intensity of the PIGs sintered at different temperature other than 700 °C were all enhanced after hydrogen annealing. Hence, the hydrogen annealing was an excellent measure to strengthen the PL intensity of PIGs, but the excessive sintering temperature was not beneficial to improve the PL intensity of the PIG. Fig. 2a–b exhibits the relationship between increasing ratio of the peak intensity and the different sintering temperature. Fig. 2a reveals that the enhancement percentage of the PLE spectral peak intensity was improved from 21.00% to 207.90% as the sintering temperature varied after hydrogen annealing, and Fig. 2b displays that the enhancement increasing ratio of the PL spectral peak intensity was raised from
Table 3 Relative percentage of Ce3 + in PIG sintered at 600 °C after annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.672 897.629 888.702 902.372
4.44 6.62 6.12 7.04
1256.826 8060.738 9242.096 11,057.264
9317.564
31.4
20,299.36
68.6
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Table 4 Relative percentage of Ce3 + in PIG sintered at 700 °C after annealing.
Ce4 + 3d5/2 Ce4 + 3d3/2 Ce3 + 3d5/2 Ce3 + 3d3/2
Peak/eV
FWHM/eV
Area/(a.u.)
Sum/(a.u.)
Relative percentage/%
884.062 899.142 888.142 903.760
3.49 7.98 6.33 5.84
615.844 14,373.751 9778.275 4783.934
14,989.595
50.7
14,562.209
49.3
Fig. 4. XRD patterns of YAG: Ce3 + phosphor and PIGs under different sintering temperatures: (a) XRD of YAG: Ce3 + phosphor; (b) XRD of PIGs.
excitation and emission peak intensity. Hence, test results indicated that high sintering temperature can also destroy the photoluminescence properties of PIG.
42.29% to 174.72% with the variation of the sintering temperature after hydrogen annealing. However, the PLE and PL intensity of PIG sintered at 700 °C was not enhanced after hydrogen annealing. The 884, 902, 881.6, and 899.9 eV binding energies correspond orderly to the Ce3 + 3d5/2, Ce3 + 3d3/2, Ce4 + 3d5/2, and Ce4 + 3d3/2 components from the standard database of XPS spectra [17,18]. Fig. 3 illustrates the XPS spectra and fitting curve of the Ce3d in PIG sintered at 600 °C and 700 °C before and after annealing. All the spectra fitting dates are listed in the Tables 1–4, including maximum binding energy, FWHM, peak area, and the relative content of Ce3 + (the ratio of peak area [Ce3 +] / peak area [Ce3 + + Ce4 +]). The test results based on the tables explained that the Ce3 + concentration of PIG decreased as the sintering temperature increased, which was ascribed to the oxidation of Ce3 +. As shown in Tables 1–2, the relative percentage of Ce3 + dispersed in PIG decreased from 51.1% to 27.9% before hydrogen annealing. The change may account for the reason why the high sintering temperature results in worse luminescence properties (Fig. 1). Only one electron in the 4f layer of Ce3 + can transit to 5d layer to produce luminescence considering the luminescence principle of YAG: Ce3 + [19,20]. When the Ce3 + ion is oxidized to Ce4 +, the excitation and emission from 4f to 5d are not realized because of no remaining electrons in the 4f layer. With respect to Table 1, the Ce3 + concentration of Table 3 increased from 51.1% to 68.6% after hydrogen annealing, mainly due to the annealing of the Ce4 + in PIGs. Consequently, the low sintering temperature and hydrogen annealing are beneficial to enhance the luminescence properties and the Ce3 + concentration of the PIGs. Fig. 4 shows the XRD pattern of YAG: Ce3 + phosphor and PIGs obtained at different sintering temperature. The pattern of Fig. 4a indicated that the diffraction peaks of YAG and the standard card (PDF#33-0040) were matched with the sintering temperature increasing [21], but obvious change in the diffraction peaks of PIG can be observed from Fig. 4b. When the sintering temperature was 700 °C, the diffraction peaks of PIG entirely disappeared because of the destruction of the lattice structure of YAG, which can lead to the decrease of the
4. Conclusion In this paper, the PIGs have been successfully prepared by the onestep melt-quenching method. The effect of hydrogen annealing on the PIGs sintered at 450–700 °C was discussed and analyzed by PL spectra, XPS and XRD. The PLE peak intensity of the PIG sintered below 700 °C was enhanced from 21.00% to 207.90% and the PL of the PIG from 42.29% to 174.72% after hydrogen annealing, which can be ascribed to the increasement of Ce3 + concentration after reducing. However, the excitation and emission spectra of PIG sintered at 700 °C entirely disappeared because of the destruction of the crystal structure around the Ce3 + ions. Hence, the hydrogen annealing and the appropriate sintering temperature can the PL and PLE intensity and the Ce3 + ion concentration. Acknowledgements This work was supported by National Nature Science Foundation of China (51302171), Science and Technology Commission of Shanghai Municipality (14500503300), Shanghai Cooperative Project (shanghaiCXY2013-61). References [1] Peng Yang, Ruixin Li, Hao Cheng, Zhen Chen, Hong Li, Mingxiang Chen, Facile preparation of patterned phosphor-in-glass with excellent luminous properties through screen-printing for high-power white light-emitting diodes, J. Alloys Compd. 693 (2017) 279–284, http://dx.doi.org/10.1016/j.jallcom.2016.09.197. [2] Daqin Chen, Weidong Xiang, Xiaojuan Liang, Jiasong Zhong, Hua Yu, Mingye Ding, Hongwei Lu, Zhenguo Ji, Advances in transparent glass–ceramic phosphors for white light-emitting diodes—a review, J. Eur. Ceram. Soc. 35 (2015) 859–869, http://dx.doi.org/10.1016/j.jeurceramsoc.2014.10.002. [3] Hoyong Yie, Sunil Kim, Yurian Kim, Hyungsun Kim, Modifying optical properties of
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