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Synthesis of Gd1−xTbxAl3(BO3)4 (0.05⩽x⩽1) and its luminescence properties under VUV excitation
ARTICLE IN PRESS
Journal of Luminescence 122–123 (2007) 1000–1002 www.elsevier.com/locate/jlumin
Synthesis of Gd1xTbxAl3(BO3)4 (0.05pxp1) and its luminescence properties under VUV excitation Xiaoxia Li, Yuhua Wang Department of Materials Science, Lanzhou University, Lanzhou 730000, PR China Available online 13 March 2006
Abstract Single phases of Gd1xTbxAl3(BO3)4 (0.05pxp1) were prepared by the thermal decomposition of the corresponding nitrates. Monitored at 541 nm, the excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1) consisted of one broad band located in the 120–179 nm range and some other bands from 179 to 290 nm. The former could be assigned to the overlapped absorptions among the f-d transition of Gd3+, the charge transfer bands of Ln3+–O2 (Ln ¼ Tb, Gd) and BO3 groups. The latter was ascribed to the 4f8-4f75d transitions of Tb3+. The maximum emission peak was observed at about 541 nm, and the optimum emission was obtained at x ¼ 0.5 under 147 nm excitation. The decay time decreased linearly with the increase of Tb3+ concentration. Compared with the phosphor Zn2SiO4:0.08Mn2+, the optimum phosphor Gd0.5Tb0.5Al3(BO3)4 exhibited about 42% emission intensity with chromaticity coordinates of (0.338, 0.579) and the shorter decay time of about 1.945 ms under 147 nm excitation. r 2006 Elsevier B.V. All rights reserved. Keywords: GdAl3(BO3)4:Tb; Phosphor; VUV
1. Introduction Much attention has been paid to phosphors for vacuum ultraviolet (VUV) due to the demands of plasma display panels (PDPs) and possible new generation of mercury-free fluorescent lamps. Tri-color phosphors for PDPs are required to have high conversion efficiency, good colorimetric purity and proper decay time under 147 nm excitation. As far as green-emitting phosphors are concerned, the most widely used one is Zn2SiO4:Mn2+, but its decay time is too long [1]. Therefore, it is urgently necessary to improve existing materials and/or exploit new phosphors. Recently, borates have been absorbing much attention because of good thermal and chemical stability and strong absorption in VUV region. GdAl3(BO3)4:Tb3+ is promising in this family for the following reasons. The crystal structure of GdAl3(BO3)4 is isomorphs with huntite CaMg3(CO3)4 [2]. There is relatively large distance between the nearest Gd3+ neighbors, and attributing to it, a high quenching concentration can be expected to exist. MoreCorresponding author. Tel.: +86 931 8912079; fax: +86 931 8913554.
E-mail address: [email protected] (Y. Wang). 0022-2313/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2006.01.350
over, GdAl3(BO3)4:Tb3+ can be anticipated to have short decay time, which can overcome the shortcoming of Zn2SiO4:Mn2+. However, systemic investigations on the luminescence properties of GdAl3(BO3)4:Tb3+ under VUV excitation are scarcely reported now. In this paper, Gd1xTbxAl3(BO3)4 (0.05pxp1) powder samples were prepared by the thermal decomposition of the corresponding nitrates. Their luminescence properties were investigated in VUV region in detail. The positions of the f–d transition of Gd3+ and the charge transfer band (CTB) of Tb3+–O2 were calculated, and compared with the experimental data. Accordingly, the luminescence mechanism under VUV excitation was tentatively proposed.
2. Experimental Gd2O3 (99.99%), Tb4O7 (99.99%), Al(NO3)3 9H2O (99%) and H3BO3 (99.5%) were used as raw materials. The stoichiometric amounts of starting materials with 20% excess of H3BO3 were weighed and dissolved completely in nitric acid. The solution was to be dried, and the resulting
ARTICLE IN PRESS X. Li, Y. Wang / Journal of Luminescence 122–123 (2007) 1000–1002
450 125
150
175
200 225 Wavelength (nm)
250
275
500
1.2 1.0 0.8 0.6 0.4
550
0.0
0.2
D4-7F3
0.2
5D -7F 4 4
b
The CTB of Eu3+–O2 in the excitation spectrum of Gd0.5Eu0.5Al3(BO3)4 centered at about 241 nm (Fig. 1(c)) and wuncorr(Eu3+) is 1.74 [8]. So wopt(O2) was obtained with about 3.12. wuncorr(Tb3+) is 0.95 [8]. Accordingly, it can be calculated that the CTB of Tb3+–O2 was at about 154 nm. As a conclusion, the broad band from 120 to 179 nm could include the f–d transition of Gd3+, the CTBs of Ln3+–O2 (Ln ¼ Tb, Gd) and the absorption of BO3 groups. The emission spectra of Gd1xTbxAl3(BO3)4 (0.05 pxp1) were similar. Fig. 2 exhibits the emission spectrum of Gd0.5Tb0.5Al3(BO3)4 under 147 nm excitation. The most intense emission peak was observed at 541 nm due to 5 D4–7F5 transition of Tb3+. The other emission peaks were ascribed to the transition 5D4 level to 7F6, 7F4, and 7F3 levels of Tb3+ respectively. Calculation of the chromaticity coordinates gave x ¼ 0.338, y ¼ 0.579, which confirms that Gd0.5Tb0.5Al3(BO3)4 has the appearance of a pure spectral green. The inset in Fig. 2 shows the emission intensity of 5 D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4
5D -7F 4 6
Relative intensity (a.u.)
a
E ct ðcm1 Þ ¼ ½wopt ðX Þ wuncorr ðMÞ 30000 cm1 .
Intensity (a.u.)
c
D(A) is about 18090 cm1 and DEGd,Ce is 45800 cm1 [6]. So we obtained that the f–d transition position of Gd3+ was at about 130 nm. This result is in very well agreement with the experimental data. The position of the CTB of Tb3+–O2 in GdAl3(BO3)4:Tb3+ can be obtained by the Jørgensen’s equation [7]:
5D -7F 4 5
Gd3+ (8S7/2-6I11/2)
All the powders appear to be white color in body. XRD patterns of Gd1xTbxAl3(BO3)4 (0.05pxp1) were recognized as a single phase. The excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1) were similar, and the most excitation intensity was obtained at x ¼ 0.5. As an example, the excitation spectrum of Gd0.5Tb0.5Al3(BO3)4 is shown in Fig. 1(a). The strongest broad band ranging from 120 to 179 nm and some other bands from 179 to 290 nm were observed monitored at 541 nm. The bands in the region from 160 to 300 nm all were attributed to the 4f8–4f75d1 transitions of Tb3+ in Ref. [3]. However, it indicated evidently that the band peaking at about 168 nm was observed in Gd0.5Tb0.5Al3(BO3)4, TbAl3(BO3)4 (Fig. 1(b)) and also Gd0.5Eu0.5Al3(BO3)4 (Fig. 1(c)). So the band from 164 to 179 nm could not be assigned to the 4f8–4f75d1 transitions absorption of Tb3+, and can be due to the absorption of BO3 groups [4]. Also, the peak at about 274 nm due to the transition of 8S7/2 to 6I11/2 of Gd3+ was observed in the excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1). This implied that the energy transfer from Gd3+ to Tb3+ had taken place. According to Ref. [4,5], the broad band below 179 nm was assigned to the overlapped absorptions of BO3 groups and the CTB of Gd3+–O2 in GdAl3(BO3)4:Eu3+. It can be seen obviously that this
EðLn; AÞ ¼ 49340 cm1 DðAÞ þ DE Ln;Ce .
0.4 0.6 x (mol)
0.8
1.0
5
3. Results and discussion
broad band consists of more than two bands in our samples of Gd1xTbxAl3(BO3)4 (0.05pxp1). Therefore, we can infer that it could include other absorptions, and they may be the f–d transition of Gd3+ and the CTB of Tb3+–O2. The position of the f–d transition of Gd3+ in GdAl3(BO3)4:Tb3+ can be calculated with the Dorenbos’ equation [6]:
Relative intensity (a.u.)
mixture was first heated at 700 1C for 3 h, and then calcined at 1150 1C for 10 h in air. The samples were characterized by Rigaku D/max 2400 X-ray powder diffractometer (XRD). Excitation and emission spectra were obtained using FLS920T combined fluorescence lifetime with VM504 vacuum monochromator as light source. The VUV excitation spectra were corrected by dividing the excitation intensity of sodium salicylate at the same measurement conditions.
1001
600 650 Wavelength (nm)
700
750
800
300
Fig. 1. Excitation spectra of (a) Gd0.5Tb0.5Al3(BO3)4 (lem ¼ 541 nm), (b) TbAl3(BO3)4 (lem ¼ 541 nm) and (c) Gd0.5Eu0.5Al3(BO3)4 (lem ¼ 613 nm).
Fig. 2. The emission spectrum of Gd0.5Tb0.5Al3(BO3)4 (lex ¼ 147 nm). The inset exhibits the relative emission intensity of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) under different Tb3+ concentrations (lex ¼ 147 nm, lem ¼ 541 nm).
ARTICLE IN PRESS X. Li, Y. Wang / Journal of Luminescence 122–123 (2007) 1000–1002
1002
BaAl12O19:Mn2+ [9]. So it can be interpreted that the increasing defect impurities are likely to decrease the Tb3+ decay time at Tb3+ higher concentration.
Decay time (ms)
Normalized intensity (a.u.)
1
0.36788
0.13534
2.6 2.4 2.2 2.0 1.8 1.6 1.4
4. Conclusions 0.0 0.2 0.4 0.6 0.8 1.0 x (mol)
0.04979
0.01832
0
2
4
6 8 Decay time (ms)
10
12
Fig. 3. The decay curve of 5D4–7F5 transition of Tb3+ in Gd0.5Tb0.5Al3(BO3)4 (lex ¼ 147 nm). The inset shows the concentration dependence of the decay time of 5D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) (lex ¼ 147 nm).
(0.05pxp1) plotted against the concentration of Tb3+ under 147 nm excitation. The optimum emission was obtained at a concentration of x ¼ 0.5, namely, the concentration quenching occurred here. The reason for so much high quenching concentration might mainly be due to the relatively large distance between rare earth ions in the crystal structure of GdAl3(BO3)4. This needs further investigation. Compared with the phosphor Zn2SiO4: 0.08Mn2+, the emission intensity of Gd0.5Tb0.5Al3(BO3)4 was about 42%. This implies that Gd0.5Tb0.5Al3(BO3)4 is a potential green VUV phosphor. Fig. 3 gives the decay curve of 5D4–7F5 transition of Tb3+ for Gd0.5Tb0.5Al3(BO3)4 under 147 nm excitation. According to the experimental data, the decay curve can be well fitted by single exponential equation. The decay time extracted from the fitted curve is about 1.945 ms (the time to decay 1/e of the original intensity), while the decay time of Zn2SiO4:0.08Mn2+ is about 4.236 ms. So Gd0.5 Tb0.5Al3(BO3)4 has more proper decay time and meets what is required in PDPs. The inset in Fig. 3 shows the decay time of 5D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) as a function of Tb3+ concentration under 147 nm excitation. It indicated that the decay time decreased linearly with the increase of Tb3+ concentration and was in the range from 1.431 to 2.435 ms. The similar phenomenon for Mn2+ was observed in
Single phase of Gd1xTbxAl3(BO3)4 (0.05pxp1) were prepared and their luminescence properties were investigated under VUV excitation. The broad band from 120 to 179 nm was assigned to the overlapped absorptions among the f–d transition of Gd3+, the CTBs of Ln3+–O2 (Ln ¼ Tb, Gd) and BO3 groups in the excitation spectrum of Gd0.5Tb0.5Al3(BO3)4. Gd0.5Tb0.5Al3(BO3)4 with chromaticity coordinates of (0.338, 0.579) and the decay time of about 1.945 ms exhibited about 42% emission intensity of Zn2SiO4:0.08Mn2+ under 147 nm excitation. It can be concluded that GdAl3(BO3)4:Tb3+ is undoubtedly a potential green VUV phosphor owing to its favorable luminescence properties. Acknowledgments This work was supported by Program for New Century Excellent Talents in University (NCET, 04-0978), Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 20040730019) and The Key Science Research Project of Ministry of Education of China (105170). References [1] C.R. Ronda, J. Lumin. 72–74 (1997) 49. [2] A.D. Mills, Inorg. Chem. 1 (1962) 960. [3] H.P. You, G.Y. Hong, X.Q. Zeng, C.-H. Kim, C.-H. Pyun, B.-Y. Yu, H.-S. Bae, J. Phys. Chem. Solids 61 (12) (2000) 1985. [4] Y.H. Wang, K. Uheda, H. Takizawa, U. Mizumoto, T. Endo, J. Electrochem. Soc. 148 (8) (2001) 430. [5] Y.H. Wang, T. Endo, X. Guo, Y. Murakami, M. Ushirozawa, J. SID 12/4 (1) (2004) 1. [6] P. Dorenbos, J. Lumin. 91 (2000) 155. [7] R. Resfeld, C.K. Jørgensen, Lasers and Excite States of Rare Earth, Springer, Berlin, 1977, p. 45. [8] Q. Su, J. Rare Earths (special issue), in: Proceedings of the Second Conference on Rare Earth Development and Application, 1991, p. 765. [9] K.-S. Sohn, E.S. Park, C.H. Kim, H.D. Park, J. Electrochem. Soc. 147 (11) (2000) 4368.
Journal of Luminescence 122–123 (2007) 1000–1002 www.elsevier.com/locate/jlumin
Synthesis of Gd1xTbxAl3(BO3)4 (0.05pxp1) and its luminescence properties under VUV excitation Xiaoxia Li, Yuhua Wang Department of Materials Science, Lanzhou University, Lanzhou 730000, PR China Available online 13 March 2006
Abstract Single phases of Gd1xTbxAl3(BO3)4 (0.05pxp1) were prepared by the thermal decomposition of the corresponding nitrates. Monitored at 541 nm, the excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1) consisted of one broad band located in the 120–179 nm range and some other bands from 179 to 290 nm. The former could be assigned to the overlapped absorptions among the f-d transition of Gd3+, the charge transfer bands of Ln3+–O2 (Ln ¼ Tb, Gd) and BO3 groups. The latter was ascribed to the 4f8-4f75d transitions of Tb3+. The maximum emission peak was observed at about 541 nm, and the optimum emission was obtained at x ¼ 0.5 under 147 nm excitation. The decay time decreased linearly with the increase of Tb3+ concentration. Compared with the phosphor Zn2SiO4:0.08Mn2+, the optimum phosphor Gd0.5Tb0.5Al3(BO3)4 exhibited about 42% emission intensity with chromaticity coordinates of (0.338, 0.579) and the shorter decay time of about 1.945 ms under 147 nm excitation. r 2006 Elsevier B.V. All rights reserved. Keywords: GdAl3(BO3)4:Tb; Phosphor; VUV
1. Introduction Much attention has been paid to phosphors for vacuum ultraviolet (VUV) due to the demands of plasma display panels (PDPs) and possible new generation of mercury-free fluorescent lamps. Tri-color phosphors for PDPs are required to have high conversion efficiency, good colorimetric purity and proper decay time under 147 nm excitation. As far as green-emitting phosphors are concerned, the most widely used one is Zn2SiO4:Mn2+, but its decay time is too long [1]. Therefore, it is urgently necessary to improve existing materials and/or exploit new phosphors. Recently, borates have been absorbing much attention because of good thermal and chemical stability and strong absorption in VUV region. GdAl3(BO3)4:Tb3+ is promising in this family for the following reasons. The crystal structure of GdAl3(BO3)4 is isomorphs with huntite CaMg3(CO3)4 [2]. There is relatively large distance between the nearest Gd3+ neighbors, and attributing to it, a high quenching concentration can be expected to exist. MoreCorresponding author. Tel.: +86 931 8912079; fax: +86 931 8913554.
E-mail address: [email protected] (Y. Wang). 0022-2313/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2006.01.350
over, GdAl3(BO3)4:Tb3+ can be anticipated to have short decay time, which can overcome the shortcoming of Zn2SiO4:Mn2+. However, systemic investigations on the luminescence properties of GdAl3(BO3)4:Tb3+ under VUV excitation are scarcely reported now. In this paper, Gd1xTbxAl3(BO3)4 (0.05pxp1) powder samples were prepared by the thermal decomposition of the corresponding nitrates. Their luminescence properties were investigated in VUV region in detail. The positions of the f–d transition of Gd3+ and the charge transfer band (CTB) of Tb3+–O2 were calculated, and compared with the experimental data. Accordingly, the luminescence mechanism under VUV excitation was tentatively proposed.
2. Experimental Gd2O3 (99.99%), Tb4O7 (99.99%), Al(NO3)3 9H2O (99%) and H3BO3 (99.5%) were used as raw materials. The stoichiometric amounts of starting materials with 20% excess of H3BO3 were weighed and dissolved completely in nitric acid. The solution was to be dried, and the resulting
ARTICLE IN PRESS X. Li, Y. Wang / Journal of Luminescence 122–123 (2007) 1000–1002
450 125
150
175
200 225 Wavelength (nm)
250
275
500
1.2 1.0 0.8 0.6 0.4
550
0.0
0.2
D4-7F3
0.2
5D -7F 4 4
b
The CTB of Eu3+–O2 in the excitation spectrum of Gd0.5Eu0.5Al3(BO3)4 centered at about 241 nm (Fig. 1(c)) and wuncorr(Eu3+) is 1.74 [8]. So wopt(O2) was obtained with about 3.12. wuncorr(Tb3+) is 0.95 [8]. Accordingly, it can be calculated that the CTB of Tb3+–O2 was at about 154 nm. As a conclusion, the broad band from 120 to 179 nm could include the f–d transition of Gd3+, the CTBs of Ln3+–O2 (Ln ¼ Tb, Gd) and the absorption of BO3 groups. The emission spectra of Gd1xTbxAl3(BO3)4 (0.05 pxp1) were similar. Fig. 2 exhibits the emission spectrum of Gd0.5Tb0.5Al3(BO3)4 under 147 nm excitation. The most intense emission peak was observed at 541 nm due to 5 D4–7F5 transition of Tb3+. The other emission peaks were ascribed to the transition 5D4 level to 7F6, 7F4, and 7F3 levels of Tb3+ respectively. Calculation of the chromaticity coordinates gave x ¼ 0.338, y ¼ 0.579, which confirms that Gd0.5Tb0.5Al3(BO3)4 has the appearance of a pure spectral green. The inset in Fig. 2 shows the emission intensity of 5 D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4
5D -7F 4 6
Relative intensity (a.u.)
a
E ct ðcm1 Þ ¼ ½wopt ðX Þ wuncorr ðMÞ 30000 cm1 .
Intensity (a.u.)
c
D(A) is about 18090 cm1 and DEGd,Ce is 45800 cm1 [6]. So we obtained that the f–d transition position of Gd3+ was at about 130 nm. This result is in very well agreement with the experimental data. The position of the CTB of Tb3+–O2 in GdAl3(BO3)4:Tb3+ can be obtained by the Jørgensen’s equation [7]:
5D -7F 4 5
Gd3+ (8S7/2-6I11/2)
All the powders appear to be white color in body. XRD patterns of Gd1xTbxAl3(BO3)4 (0.05pxp1) were recognized as a single phase. The excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1) were similar, and the most excitation intensity was obtained at x ¼ 0.5. As an example, the excitation spectrum of Gd0.5Tb0.5Al3(BO3)4 is shown in Fig. 1(a). The strongest broad band ranging from 120 to 179 nm and some other bands from 179 to 290 nm were observed monitored at 541 nm. The bands in the region from 160 to 300 nm all were attributed to the 4f8–4f75d1 transitions of Tb3+ in Ref. [3]. However, it indicated evidently that the band peaking at about 168 nm was observed in Gd0.5Tb0.5Al3(BO3)4, TbAl3(BO3)4 (Fig. 1(b)) and also Gd0.5Eu0.5Al3(BO3)4 (Fig. 1(c)). So the band from 164 to 179 nm could not be assigned to the 4f8–4f75d1 transitions absorption of Tb3+, and can be due to the absorption of BO3 groups [4]. Also, the peak at about 274 nm due to the transition of 8S7/2 to 6I11/2 of Gd3+ was observed in the excitation spectra of Gd1xTbxAl3(BO3)4 (0.05pxo1). This implied that the energy transfer from Gd3+ to Tb3+ had taken place. According to Ref. [4,5], the broad band below 179 nm was assigned to the overlapped absorptions of BO3 groups and the CTB of Gd3+–O2 in GdAl3(BO3)4:Eu3+. It can be seen obviously that this
EðLn; AÞ ¼ 49340 cm1 DðAÞ þ DE Ln;Ce .
0.4 0.6 x (mol)
0.8
1.0
5
3. Results and discussion
broad band consists of more than two bands in our samples of Gd1xTbxAl3(BO3)4 (0.05pxp1). Therefore, we can infer that it could include other absorptions, and they may be the f–d transition of Gd3+ and the CTB of Tb3+–O2. The position of the f–d transition of Gd3+ in GdAl3(BO3)4:Tb3+ can be calculated with the Dorenbos’ equation [6]:
Relative intensity (a.u.)
mixture was first heated at 700 1C for 3 h, and then calcined at 1150 1C for 10 h in air. The samples were characterized by Rigaku D/max 2400 X-ray powder diffractometer (XRD). Excitation and emission spectra were obtained using FLS920T combined fluorescence lifetime with VM504 vacuum monochromator as light source. The VUV excitation spectra were corrected by dividing the excitation intensity of sodium salicylate at the same measurement conditions.
1001
600 650 Wavelength (nm)
700
750
800
300
Fig. 1. Excitation spectra of (a) Gd0.5Tb0.5Al3(BO3)4 (lem ¼ 541 nm), (b) TbAl3(BO3)4 (lem ¼ 541 nm) and (c) Gd0.5Eu0.5Al3(BO3)4 (lem ¼ 613 nm).
Fig. 2. The emission spectrum of Gd0.5Tb0.5Al3(BO3)4 (lex ¼ 147 nm). The inset exhibits the relative emission intensity of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) under different Tb3+ concentrations (lex ¼ 147 nm, lem ¼ 541 nm).
ARTICLE IN PRESS X. Li, Y. Wang / Journal of Luminescence 122–123 (2007) 1000–1002
1002
BaAl12O19:Mn2+ [9]. So it can be interpreted that the increasing defect impurities are likely to decrease the Tb3+ decay time at Tb3+ higher concentration.
Decay time (ms)
Normalized intensity (a.u.)
1
0.36788
0.13534
2.6 2.4 2.2 2.0 1.8 1.6 1.4
4. Conclusions 0.0 0.2 0.4 0.6 0.8 1.0 x (mol)
0.04979
0.01832
0
2
4
6 8 Decay time (ms)
10
12
Fig. 3. The decay curve of 5D4–7F5 transition of Tb3+ in Gd0.5Tb0.5Al3(BO3)4 (lex ¼ 147 nm). The inset shows the concentration dependence of the decay time of 5D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) (lex ¼ 147 nm).
(0.05pxp1) plotted against the concentration of Tb3+ under 147 nm excitation. The optimum emission was obtained at a concentration of x ¼ 0.5, namely, the concentration quenching occurred here. The reason for so much high quenching concentration might mainly be due to the relatively large distance between rare earth ions in the crystal structure of GdAl3(BO3)4. This needs further investigation. Compared with the phosphor Zn2SiO4: 0.08Mn2+, the emission intensity of Gd0.5Tb0.5Al3(BO3)4 was about 42%. This implies that Gd0.5Tb0.5Al3(BO3)4 is a potential green VUV phosphor. Fig. 3 gives the decay curve of 5D4–7F5 transition of Tb3+ for Gd0.5Tb0.5Al3(BO3)4 under 147 nm excitation. According to the experimental data, the decay curve can be well fitted by single exponential equation. The decay time extracted from the fitted curve is about 1.945 ms (the time to decay 1/e of the original intensity), while the decay time of Zn2SiO4:0.08Mn2+ is about 4.236 ms. So Gd0.5 Tb0.5Al3(BO3)4 has more proper decay time and meets what is required in PDPs. The inset in Fig. 3 shows the decay time of 5D4–7F5 transition of Tb3+ in Gd1xTbxAl3(BO3)4 (0.05pxp1) as a function of Tb3+ concentration under 147 nm excitation. It indicated that the decay time decreased linearly with the increase of Tb3+ concentration and was in the range from 1.431 to 2.435 ms. The similar phenomenon for Mn2+ was observed in
Single phase of Gd1xTbxAl3(BO3)4 (0.05pxp1) were prepared and their luminescence properties were investigated under VUV excitation. The broad band from 120 to 179 nm was assigned to the overlapped absorptions among the f–d transition of Gd3+, the CTBs of Ln3+–O2 (Ln ¼ Tb, Gd) and BO3 groups in the excitation spectrum of Gd0.5Tb0.5Al3(BO3)4. Gd0.5Tb0.5Al3(BO3)4 with chromaticity coordinates of (0.338, 0.579) and the decay time of about 1.945 ms exhibited about 42% emission intensity of Zn2SiO4:0.08Mn2+ under 147 nm excitation. It can be concluded that GdAl3(BO3)4:Tb3+ is undoubtedly a potential green VUV phosphor owing to its favorable luminescence properties. Acknowledgments This work was supported by Program for New Century Excellent Talents in University (NCET, 04-0978), Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 20040730019) and The Key Science Research Project of Ministry of Education of China (105170). References [1] C.R. Ronda, J. Lumin. 72–74 (1997) 49. [2] A.D. Mills, Inorg. Chem. 1 (1962) 960. [3] H.P. You, G.Y. Hong, X.Q. Zeng, C.-H. Kim, C.-H. Pyun, B.-Y. Yu, H.-S. Bae, J. Phys. Chem. Solids 61 (12) (2000) 1985. [4] Y.H. Wang, K. Uheda, H. Takizawa, U. Mizumoto, T. Endo, J. Electrochem. Soc. 148 (8) (2001) 430. [5] Y.H. Wang, T. Endo, X. Guo, Y. Murakami, M. Ushirozawa, J. SID 12/4 (1) (2004) 1. [6] P. Dorenbos, J. Lumin. 91 (2000) 155. [7] R. Resfeld, C.K. Jørgensen, Lasers and Excite States of Rare Earth, Springer, Berlin, 1977, p. 45. [8] Q. Su, J. Rare Earths (special issue), in: Proceedings of the Second Conference on Rare Earth Development and Application, 1991, p. 765. [9] K.-S. Sohn, E.S. Park, C.H. Kim, H.D. Park, J. Electrochem. Soc. 147 (11) (2000) 4368.