Preparation of Ca2SnO4:Tb3+, R3+ phosphors (R3+ = B3+, Al3+ or Ga3+) and the dependence of their luminescence on R3+ cations

Optical Materials 91 (2019) 408–412

Contents lists available at ScienceDirect

Optical Materials journal homepage: www.elsevier.com/locate/optmat

Preparation of Ca2SnO4:Tb3+, R3+ phosphors (R3+ = B3+, Al3+ or Ga3+) and the dependence of their luminescence on R3+ cations

T

Yulin Chen, Junfeng Ma∗, Qi Chen, Shanqiao Cao, Xun Wang School of Renewable Energy, North China Electric Power University, Beijing, 102206, China

A R T I C LE I N FO

A B S T R A C T

Keywords: Oxide Phosphors Solid state reaction Luminescence X-ray diffraction

Ca2SnO4:Tb3+ phosphors co-doped by R3+ cations (R3+ = B3+, Al3+, Ga3+) can be prepared by a solid-state reaction. They are fine solid solutions, which have been studied in detail by XRD, photoluminescence spectra, and decay curves. The results show that their luminescence can be effectively improved by co-doping R3+ cations and adding Al3+ cation is superior to that with other two dopants whether in fluorescence or phosphorescence. The concentration quenching effect will weaken their luminescence beyond m = 0.07 when Al3+ cation is co-doped. The distortion of host lattice and change of local crystal field symmetry around Tb3+ due to co-doping R3+ can enhance their fluorescence. The formation and increase of oxygen vacancy (V••O) predominate in improving their phosphorescence, while the single bond strength of R-O also plays an important role.

1. Introduction Long afterglow phosphors belong to an energy-storing material which can continue to emit light after the excitation is stopped [1]. This property makes them find a wide application in many fields such as emergency lighting, electronic display, high energy ray detection, image storage and optical memory [2,3], and even applications in medical diagnostics, vivo bio-imaging and solar energy utilization [4–6]. In the past decades, much attention has been paid to alkaline earth aluminate or silicates such as SrAl2O4:Eu2+, Dy3+ [7] and Sr2MgSi2O7:Eu2+ Dy3+ [8], but few researches on Ca2SnO4 family were reported before 2005, in which Ca2SnO4:Tb3+ with a green emission was reported at first. Since then, long afterglow phosphors based on stannate have attracted much attention of materials researchers. Ca2SnO4 can be used as an excellent matrix material for many long afterglow phosphors such as Ca2SnO4:Sm3+ [1], Ca2SnO4:Tb3+ [9], Ca2SnO4:Pr3+ [10], Ca2SnO4:Eu3+ [11], Ca2SnO4:Er3+ [12], and Ca2SnO4:Dy3+ [13] since it possesses optically inert and stable [SnO4]4ionic group [13–15], and one-dimensional chain structure made up of [SnO6] octahedral which is very easy to implant other ions into the host lattice and create traps located at suitable depths that can store the excitation energy and emit light at room temperature [13,16–18]. More recently, many efforts have been made for enhancing their luminescence; e.g. some suitable co-doped cations were used to improving the luminescence of alkaline earth stannate systems: CaSnO3:Tb3+, R+ (Li+/Na+/K+) [19], CaSnO3:Tb3+, Mg2+ [20],

∗

Ca2SnO4:Eu3+, Y3+ [21], Ca2SnO4:Eu3+, Gd3+ [16], Sr2SnO4:Eu3+, Ti4+ [22], and CaSnO4:Tb3+, Li+ [23]. However, these studies mainly focus on the co-doping of alkaline metal cation with Tb3+ or co-doping of rare earth cation with Tb3+, while the co-doping of R3+ (R3+ = B3+, Al3+ or Ga3+) has been scarcely reported. In the present study, we attempt to reveal the influence of R3+ as a co-dopant (R3+ = B3+, Al3+, Ga3+) on the luminescence performance of Ca2SnO4:Tb3+ phosphors, and determine which one is the best, and then investigate the effect of doped quantity on their luminescence. To the best of our knowledge, no such studies have been reported. Therefore, this study is of important significance whether in improving the luminescence performance of Ca2SnO4:Tb3+ phosphor or broadening the usage of R3+ cation (R3+ = B3+, Al3+ or Ga3+). 2. Experimental 2.1. Materials and preparation Ca2SnO4:Tb3+ phosphors with different co-doped cations were prepared at 1350 °C using a solid-state reaction technique. CaCO3, SnO2, Tb4O7, H3BO3, Al(OH)3, and Ga2O3 were used as starting materials, here all the materials are analytically pure without further purification. They were respectively weighed out according to the nominal 3+ 3+ composition of Ca1.999Sn0.93O4:Tb3+ = B3+, Al3+ or 0.001, R0.07 (R 3+ 3+ 3+ Ga ) and Ca1.999Sn1-mO4:Tb0.001, Alm (m = 0.01, 0.03, 0.05, 0.07, and 0.10). Each sample was thoroughly mixed for 1 h in an agate

Corresponding author. E-mail address: [email protected] (J. Ma).

https://doi.org/10.1016/j.optmat.2019.03.056 Received 6 December 2018; Received in revised form 25 March 2019; Accepted 30 March 2019 Available online 05 April 2019 0925-3467/ © 2019 Elsevier B.V. All rights reserved.

Optical Materials 91 (2019) 408–412

Y. Chen, et al.

3+ 3+ 3+ Fig. 1. XRD patterns (a) and emission spectra (b) of Ca1.999SnO4:Tb3+ = B3+, Al3+ or Ga3+) phosphors, prepared at 1350 °C 0.001 and Ca1.999Sn0.93O4:Tb0.001, R0.07 (R by the solid-state reaction (Dotted rectangle range: frequency doubled reflection).

reasons should be attributed to the formation of substitutional solid solution and the change of local crystal field symmetry around Tb3+ induced by adding R3+. Taking the ionic radius of R3+ into account, R3+ would substitute Sn4+ ions rather than Ca2+ since their ionic radii are close to each other (rSn4+ = 0.69 nm, rB3+ = 0.41 nm, rAl3+ = 0.54 nm, and rGa3+ = 0.62 nm, while rCa2+ = 1.00 nm) [24–26]. Here, the non-equivalent substitution exists in all the samples co-doped by R3+, but the addition of Ga3+ have a smaller influence on the local crystal field symmetry around Tb3+ than that of other two since Ga3+ has nearly equal ionic radius to that of Sn4+. Nevertheless, with the increase of the ionic radius difference between R3+ and Sn4+, the distortion of the local crystal field symmetry around Tb3+ increases, their emission will be intensified. Therefore, the fluorescence of Ca2SnO4:Tb3+ phosphor with co-doped Al3+ is better than that with Ga3+. Nevertheless, it is noteworthy that co-doping B3+ is not as good as the former Al3+ and Ga3+, though a significant increase in emission intensity can be also found. The reason may originate from the stronger strength of B-O bond (498 KJ/mol) than that of Al-O (251 KJ/mol) and Ga-O (279 KJ/mol) [27], constructing a stronger crystal structure to result in a smaller increase in emission intensity. Fig. 1(b) indicates that the best fluorescence of Ca2SnO4:Tb3+ phosphor can be obtained when Al3+ is used as a co-dopant. The problem then is how their fluorescence varies with the doped quantity of Al3+. Fig. 2(a) shows the influence of doped Al3+ quantity on their emission intensity, it can be seen that their emission intensity increases with the increase of Al3+ addition from m = 0 to m = 0.07, and that beyond m = 0.07, on continually increasing Al3+ quantity, their emission intensity will conversely decrease due to concentration quenching effect [28]. The results illustrate that the best fluorescence performance can be reached at m = 0.07. 3+ Fig. 2(b) also presents XRD patterns of Ca1.999Sn1-mO4:Tb3+ 0.001, Alm 3+ phosphors with different doped quantity of Al . When m value was changed from 0 to 0.10, all the samples showed a single phase, and no secondary phase was detected by XRD technique, well consist with the reported data of Ca2SnO4 (JCPDS NO. 20–0241). It indicates that the as3+ prepared Ca1.999Sn1-mO4:Tb3+ phosphors (m = 0.01, 0.03, 0.001, Alm 0.05, 0.07, and 0.10) are fine solid solutions with Tb3+ and Al3+ as codopants. Fig. 3(a) and Fig. 3(b) show the afterglow decay curves of 3+ 3+ 3+ Ca1.999SnO4: Tb3+ = B3+, 0.001 and Ca1.999Sn0.93O4:Tb0.001, R0.07 (R 3+ 3+ 3+ 3+ Al or Ga ), and Ca1.999Sn1-mO4:Tb0.001, Alm (m = 0, 0.01, 0.03, 0.05, 0.07, and 0.10) phosphors, respectively. Here, each afterglow

mortar before it was loaded into corundum crucibles and then calcined under a weak reducing atmosphere at 1350 °C for 4 h. After cooling, they were again ground in an agate mortar for their characterization and investigation. 2.2. Characterization of samples The phase compositions of the as-prepared samples were identified by an X-ray powder diffractometer with Cu Kα radiation (XRD, D8 Advance, Bruker, Germany), Their emission spectra and decay curves were recorded on a Hitachi F-4600 fluorescence spectrometer at room temperature with Xe lamp as a light source. Here, the same amount of sample (0.50 g) was used for each measurement. The emission wavelength scan mode was used for the measurement of emission spectra (The photomultiplier voltage: 400 V, and scan speed: 240 nm/min), and time scan mode used for the decay curves (The photomultiplier voltage: 1000 V, under the irradiation of 255 nm for 3 min). 3. Results and discussion Fig. 1(a) shows XRD patterns of Ca1.999SnO4: Tb3+ 0.001 and 3+ 3+ Ca1.999Sn0.93O4: Tb3+ = B3+, Al3+ or Ga3+) samples. 0.001, R0.07 (R Obviously, these phosphors with or without co-dopants exhibit a single phase, no secondary impurities can be found. All diffraction peaks for each sample are in good agreement with the standard data of Ca2SnO4 (JCPDS NO. 20–0241). It means that adding 7 mol % (m = 0.07) of codopants didn't have a significant impact on Ca2SnO4 structure. As mentioned before, the effect of some co-dopants, especially alkaline or alkaline earth metal cations, on the luminescence performance of Ca2SnO4: Tb3+ phosphors have been reported, but there are few researches on trivalent cations R3+ (R3+ = B3+, Al3+ or Ga3+) as codopants. Fig. 1(b) displays their emission spectra when different trivalent cations (B3+, Al3+ or Ga3+) were added, that of Ca1.999SnO4: Tb3+ 0.001 sample is also plotted for comparison. The results show that codoping R3+ cations can effectively enhance the emission intensity of Ca1.999SnO4: Tb3+ 0.001 phosphors. Here, similar to reference [23], several bands appearing respectively at 483, 545, 589, and 622 nm are also observed, they can be attributed to the transitions from 5D4 to 7Fj (j = 6, 5, 4, 3) of Tb3+ [9,20]. In addition, the emission peaks near 510 nm results from the frequency-doubled reflection [23]. Obviously, among them, adding Al3+ is superior to that of other two dopants. The 409

Optical Materials 91 (2019) 408–412

Y. Chen, et al.

3+ 3+ Fig. 2. Variation of emission intensity of Ca1.999Sn1-mO4:Tb3+ (a), and their XRD patterns (b) (Dotted rectangle 0.001, Alm phosphors with the doped quantity of Al range: frequency doubled reflection).

decay curve in Fig. 3 was also fitted based on equation (1) [9]:

I = I0 + I1 exp (−t / t1) + I2 exp (−t / t2)

Table 1 3+ Fitting parameters of afterglow decay curves for Ca1.999Sn1-mO4:Tb3+ 0.01, R0.07 phosphors.

(1)

Samples

where I is afterglow intensity, I0, I1, and I2 are constants, the rapid and slow decay process can be determined by t1 and t2, respectively. The good fitting results were obtained, and their fitting parameters shown in Table 1 and Table 2. The larger the value of t2, the longer the afterglow duration of sample is. Obviously, the afterglow performance 3+ 3+ of Ca1.999Sn0.93O4: Tb3+ as co-dopant is 0.001, R0.07 phosphor with Al 3+ 3+ superior to that of other two (B or Ga ); and when Al3+ is added, the best afterglow performance can be obtained at m = 0.07, while the afterglow decline beyond 0.07 should be assigned to concentration quenching effect [28]. In the present study, compared with Ca2SnO4:Tb3+ phosphor with single-doping Tb3+ [9], co-doping R3+ in Ca2SnO4:Tb3+ (R3+ = B3+,

3+

doping No R Co-doping B3+ Co-dopingAl3+ Co-dopingGa3

t1 (s)

t2 (s)

2.08 4.33 8.89 6.47

15.98 20.93 44.46 21.80

Al3+ or Ga3+) will result in the formation of more V••O for charge compensation besides distorting the host lattice and changing the local crystal field symmetry around Tb3+ to enhance their emission intensity, while the formation and increase of V••O will be beneficial to the improvement of their afterglow performance [29,30].

3+ 3+ 3+ Fig. 3. Afterglow decay curves of the as-prepared Ca1.999SnO4: Tb3+ = B3+, Al3+or Ga3+) phosphors (a), and effect of 0.001 and Ca1.999Sn0.93O4:Tb0.001, R0.07 (R 3+ doped Al3+ quantity on the afterglow performance of Ca1.999Sn1-mO4:Tb3+ 0.001, Alm phosphors (b).

410

Optical Materials 91 (2019) 408–412

Y. Chen, et al.

Declaration of interests

Table 2 3+ Fitting parameters of afterglow decay curves for Ca1.999Sn1-mO4:Tb3+ 0.01, Alm phosphors. Samples (m)

t1 (s)

t2 (s)

0.00 0.01 0.03 0.05 0.07 0.10

2.08 3.48 4.69 4.82 8.89 5.03

15.98 20.12 21.38 22.17 44.46 21.68

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Appendix A. Supplementary data Supplementary data related to this article can be found at https:// doi.org/10.1016/j.optmat.2019.03.056. References

For example, in the case of B3+, just like the role of B3+ ion in CaAl12O19:Mn4+, Bi3+, B3+ [24] or in SrAl2O4:Eu3+, Dy3+, B3+ [31], co-doping B3+ will lead to the shrinkage of the host lattice to change the local crystal field symmetry around activators (Tb3+), and make more activators are easy to occupy the host lattice sites with the incorporation of B3+. Thus, the energy transfer efficiency between matrix and activators will be elevated, enhancing their emission intensity [32,33]. In addition, the formation and increase of V••O, induced by the non-equivalent substitution between B3+ and Sn4+, will also improve the afterglow performance of Ca2SnO4:Tb3+ phosphor. Moreover, since the electronegativity of boron is higher than that of stannum, like in reference [31], Tb3+ ions will more easily connect with [BO4] group to form so-called acceptor-type defect center, which can capture free holes. Therefore, the afterglow performance of Ca2SnO4:Tb3+ phosphor can be effectively improved by co-doping B3+. As for Al3+ and Ga3+, they more effectively enhanced the luminescence of Ca2SnO4:Tb3+ phosphor. The remarkable improvement in their emission intensity, e.g. in Ca2SnO4:Tb3+, Al3+, can be assigned to the change of the local crystal field symmetry around Tb3+ due to codoping Al3+, and the formation of Tb-O-Al bonds, originated from the non-equivalent substitution of Al'Sn, can weaken Tb-O bond and relax the lattice strains to enhance Tb3+ emission [34]. Generally, the afterglow performance of long afterglow phosphors would decrease owing to non-radiative interactions, which are most likely caused by RE3+clustering like Tb3+ or due to structural defects in host which absorb energy from excited ions [35]. Therefore, adding Al3+ as a codopant in the present study, besides producing more V˙˙O, will lead to the formation of Tb-O-Al bonds, which further promotes radiative transitions and enhances their afterglow performance by reducing RE3+clustering and inhibiting non-radiative processes [36–38]. Moreover, the afterglow performance also is relied on their matrix framework to a certain extent. The stronger single bond strength of R-O will result in the formation of the stronger matrix framework, which makes the release process of charge carriers more difficult [39], weakening their afterglow performance. Here, B-O bond > Ga-O bond > Al-O bond in the order of the single bond strength, so it is reasonable that the Ca2SnO4:Tb3+ phosphor co-doped by Al3+ cations with the weakest single bond strength (Al-O bond) exhibits the best afterglow performance.

[1] Z. Ju, S. Zhang, X. Gao, X. Tang, W. Liu, Reddish orange long afterglow phosphor Ca2SnO4:Sm3+ prepared by sol-gel method, J. Alloy. Comp. 509 (2011) 8082–8087. [2] B. Lei, H. Zhang, W. Mai, S. Yue, Y. Liu, S. Man, Luminescent properties of orangeemitting long-lasting phosphorescence phosphor Ca2SnO4:Sm3+, Solid State Sci. 13 (2011) 525–528. [3] J. Zhou, X. Yu, T. Wang, D. Zhou, J. Qiu, Improved optical storage properties of NaAlSiO4:Tb3+ induced by Bi3+, Opt. Mater. 57 (2016) 140–145. [4] T. Maldiney, G. Sraiki, B. Viana, D. Gourier, C. Richard, D. Scherman, M. Bessodes, K. Van den Eeckhout, D. Poelman, P.F. Smet, In vivo optical imaging with rare earth doped Ca2Si5N8 persistent luminescence nanoparticles, Opt. Mater. Express 2 (2012) 261–268. [5] I.S. Kandarakis, Luminescence in medical image science, J. Lumin. 169 (2016) 553–558. [6] P.F. Smet, D. Poelman, M.P. Hehlen, Focus issue introduction: persistent phosphors, Opt. Mater. Express 2 (2012) 452–454. [7] T. Matsuzawa, Y. Aoki, N. Takeuchi, Y. Murayama, A new long phosphorescent phosphor with high brightness, SrAl2O4:Eu2+, Dy3+, J. Electrochem. Soc. 143 (1996) 2670–2673. [8] Y. Lin, Z. Tang, Z. Zhang, C.W. Nan, Luminescence of Eu2+ and Dy3+ activated R3MgSi2O8-based (R = Ca, Sr, Ba) phosphors, J. Alloy. Comp. 348 (2003) 76–79. [9] Y. Jin, Y. Hu, L. Chen, X. Wang, G. Ju, Z. Mu, Luminescent properties of Tb3+-doped Ca2SnO4 phosphor, J. Lumin. 138 (2013) 83–88. [10] Y. Jin, Y. Hu, L. Chen, X. Wang, G. Ju, Luminescent properties of a red afterglow phosphor Ca2SnO4:Pr3+, Opt. Mater. 35 (2013) 1378–1384. [11] H.M. Yang, J.X. Shi, M.L. Gong, A novel red emitting phosphor Ca2SnO4:Eu3+, J. Solid State Chem. 178 (2005) 917–920. [12] D. Zhang, M. Shi, Y. Sun, Y. Guo, C. Chang, Long afterglow property of Er3+doped Ca2SnO4 phosphor, J. Alloy. Comp. 667 (2016) 235–239. [13] M. Shi, D. Zhang, C. Chang, Dy3+:Ca2SnO4, a new yellow phosphor with afterglow behavior, J. Alloy. Comp. 639 (2015) 168–172. [14] B. Lei, B. Li, H. Zhang, W. Li, Preparation and luminescence properties of CaSnO3:Sm3+ phosphor emitting in the reddish orange region, Opt. Mater. 29 (2007) 1491–1494. [15] B. Lei, B. Li, X. Wang, W. Li, Green emitting long lasting phosphorescence (LLP) properties of Mg2SnO4:Mn2+ phosphor, J. Lumin. 118 (2006) 173–178. [16] X. Gao, Z. Zhang, C. Wang, J. Xu, Z. Ju, Y. An, W. Liu, The persistent energy transfer and effect of oxygen vacancies on red long-persistent phosphorescence phosphors Ca2SnO4: Gd3+, Eu3+, J. Electrochem. Soc. 158 (2011) J405–J408. [17] X. Xu, Y. Wang, W. Zeng, Y. Gong, Luminescence and storage properties of Smdoped alkaline-earth atannates, J. Electrochem. Soc. 158 (2011) J305–J309. [18] A. Stanulis, A. Katelnikovas, D. Enseling, D. Dutczak, S. Šakirzanovas, M.V. Bael, A. Hardy, A. Kareiva, T. Jüstel, Luminescence properties of Sm3+-doped alkaline earth ortho-stannates, Opt. Mater. 36 (2014) 1146–1152. [19] Z. Liang, J. Zhang, J. Sun, X. Li, L. Cheng, H. Zhong, S. Fu, Y. Tian, B. Chen, Enhancement of green long lasting phosphorescence in CaSnO[3]:Tb3+ by addition of alkali ions, Physica B 412 (2013) [36]–[40]. [20] T. Nakamura, M. Shima, M. Yasukawa, K. Ueda, Synthesis of Pr3+ doped or Tb3+–Mg codoped CaSnO3 perovskite phosphor by the polymerized complex method, J. Sol. Gel Sci. Technol. 61 (2012) 362–366. [21] H. Yamane, Y. Kaminaga, S. Abe, T. Yamada, Preparation, crystal structure, and photoluminescence of Ca2SnO4:Eu3+, Y3+, J. Solid State Chem. 181 (2008) 2559–2564. [22] K. Ueda, T. Yamashita, K. Nakayashiki, K. Goto, T. Maeda, K. Furui, K. Ozaki, Y. Nakachi, S. Nakamura, M. Fujisawa, T. Miyazaki, Green, orange, and magenta luminescence in strontium stannates with perovskite-related structures, J. Appl. Phys. 45 (2006) 6981–6983. [23] J. Ma, Y. Chen, X. Wang, S. Cao, Q. Chen, Luminescent performance of Ca2SnO4:Tb3+ phosphors with Li+ co-doping, Opt. Mater. 85 (2018) 86–90. [24] Y. Zhu, Z. Qiu, B. Ai, Y. Lin, W. Zhou, J. Zhang, L. Yu, Q. Mi, S. Lian, Significant improved quantum yields of CaAl12O19:Mn4+ red phosphor by co-doping Bi3+ and B3+ ions and dual applications for plant cultivations, J. Lumin. 201 (2018) 314–320. [25] S. Raya, P. Tadge, G.B. Nair, V. Chopra, S.J. Dhoble, Impact of Ga3+ on the phase transition and luminescence properties of substituted Sr2SiO4:Eu2+ phosphor synthesized from a highly homogeneous oxide precursor based on a novel water-soluble silicon compound, Ceram. Int. 44 (2018) 5506–5512. [26] H.M. Yang, J.X. Shi, M.L. Gong, A novel red emitting phosphor Ca2SnO4: Eu3+, J. Solid State Chem. 178 (2005) 917–920. [27] V. Dimitrov, T. Komatsu, Correlation among electronegativity, cation polarizability,

4. Conclusion Ca2SnO4:Tb3+ phosphors co-doped by R3+ cations were successfully prepared using a solid-state reaction method. Co-doping R3+ cations can effectively improve their luminescence, and Al3+ cation is superior to the other two dopants whether in fluorescence or phosphorescence. The concentration quenching effect will weaken their luminescence beyond m = 0.07 when Al3+ cation is co-doped. The distortion of host lattice and change of local crystal field symmetry around Tb3+ due to co-doping R3+ can enhance their fluorescence. The formation and increase of V••O predominate in improving their phosphorescence, while the single bond strength of R-O also plays an important role. 411

Optical Materials 91 (2019) 408–412

Y. Chen, et al.

[28] [29] [30]

[31] [32] [33]

[34]

optical basicity and single bond strength of simple oxides, J. Solid State Chem. 196 (2012) 574–578. G. Ju, Y. Hu, L. Chen, X. Wang, Z. Mu, Concentration quenching of persistent luminescence, Physica B 415 (2013) 1–4. H. Duan, Y.Z. Dong, Y. Huang, Y.H. Hu, X.S. Chen, The important role of oxygen vacancies in Sr2MgSi2O7phosphor, Phys. Lett. 380 (2016) 1056–1062. Z. Song, Z. Wang, L. He, R. Zhang, X. Liu, Z. Xia, W.T. Geng, Q. Liu, After-glow, luminescent thermal quenching, and energy band structure of Ce-doped yttrium aluminum-gallium garnets, J. Lumin. 192 (2017) 1278–1287. A. Nag, T.R.N. Kutty, Role of B2O3 on the phase stability and long phosphorescence of SrAl2O4:Eu, Dy, J. Alloy. Comp. 354 (2003) [221]–[231]. R.F. Qiang, S. Xiao, J.W. Ding, W. Yuan, C. Zhu, Red emission in B3+- and Li+doped SrAl2O4:Eu3+ phosphor under UV excitation, J. Lumin. 129 (2009) 826–828. J. Zhou, Y. Wang, B. Liu, Y. Lu, Effect of H3BO3 on structure and photoluminescence of BaAl12O19:Mn2+ phosphor under VUV excitation, J. Alloy. Comp. 484 (2009) 439–443. R. Cao, T. Fu, H. Xu, W. Luo, D. Peng, Z. Chen, J. Fu, Synthesis and luminescence

[35]

[36]

[37]

[38]

[39]

412

enhancement of CaTiO3:Bi3+ yellow phosphor by codoping Al3+/B3+ ions, J. Alloy. Comp. 674 (2016) 51–55. M.S. Sajna, S. Gopi, V.P. Prakashan, M.S. Sanu, C. Joseph, P.R. Biju, N.V. Unnikrishnan, Spectroscopic investigations and phonon side band analysis of Eu3+-doped multicomponent tellurite glasses, Opt. Mater. 70 (2017) [31]–[40]. M.S. Rao, V. Sudarsan, M.G. Brik, K. Bhargavi, C.S. Rao, Y. Gandhi, N. Veeraiah, The de-clustering influence of aluminumions on the emission features of Nd3+ ions in PbO–SiO2 glasses, Optic Commun. 298–299 (2013) 135–140. K. Bhargavi, V. Sudarsan, M.G. Brik, M.S. Rao, Y. Gandhi, P.N. Rao, N. Veeraiah, Influence of Al declustering on the photoluminescent properties of Pr3+ ions in PbO–SiO2 glasses, J. Non-Cryst. Solids 362 (2013) 201–206. M. Walas, P. Piotrowski, T. Lewandowski, A. Synak, M. Lapinski, W. Sadowski, B. Koscielska, Tailored white light emission in Eu3+/Dy3+ doped tellurite glass phosphors containing Al3+ ions, Opt. Mater. 79 (2018) 289–295. J. Ma, G. Qi, Y. Chen, S. Liu, S. Cao, X. Wang, Luminescence property of ZnAl2O4:Cr3+ phosphors co-doped by different Cations, Ceram. Int. 44 (2018) 11898–11900.