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Eu3+
Solid State Communications 122 (2002) 485–488 www.elsevier.com/locate/ssc
Vacuum ultraviolet excitation and photoluminescence characteristics of (Y,Gd)Al3(BO3)4/Eu3þ Kyong-Gue Leea, Byung-Yong Yub, Chong-Hong Pyunb, Sun-Il Mhoa,* a
Department of Molecular Science and Technology, Ajou University, Suwon 442-749, South Korea b Korea Institute of Science and Technology, P.O. Box 131, Seoul 130-650, South Korea Received 4 March 2002; accepted 4 April 2002 by C.N.R. Rao
Abstract Vacuum ultraviolet (VUV) excitation and photoluminescence (PL) characteristics of new red phosphors, YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ are studied. The VUV excitation spectra of both YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ are composed of two broad bands. One band with the absorption edge at ca. 168 nm is the band-gap absorption of aluminoborate and the other broad band centered at 240 nm is the charge transfer transition between Eu3þ and the neighboring oxygen anions. Rare earth ions are at the center of distorted trigonal prism, occupying non-centrosymmetric sites in the orthorhombic YAl3(BO3)4 lattices. The PL spectra of YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ show the strongest emission line at 617 nm due to the forced electric dipole 5D0 ! 7F2 transition of Eu3þ ion, whose luminescent chromaticity coordinates are (0.67, 0.33). q 2002 Elsevier Science Ltd. All rights reserved. PACS: 78.55.2m Keywords: E. Luminescence; C. Point of symmetry of defects
1. Introduction Plasma display panels (PDP) are regarded as the most promising candidates for large sized flat panel displays (FPD) [1 – 4]. Phosphors for the application in PDP are required to have high conversion efficiency by the VUV radiation of 147 and/or 172 nm from the Xe gas plasma [3 – 8]. Refractory oxide compounds with aluminate, silicate, or borate groups have strong absorption in the VUV region [5 – 9]. At present, the most widely used redemitting phosphor for PDP is (Y,Gd)BO3/Eu3þ. The Eu3þ site has inversion symmetry in (Y,Gd)BO3, as in Ba2GdNbO5, NaLuO2, and InBO3, whereas luminescent Eu3þ ions in commercial red phosphors such as YVO4, Y2O3, and Y2O2S occupy the sites that have no inversion symmetry [10,11]. If a rare-earth ion in the crystal lattice occupies a site with inversion symmetry, optical transitions between levels of the 4fn configuration are strictly forbidden * Corresponding author. Tel.: þ82-31-219-2599; fax: þ 82-31219-1615. E-mail address: [email protected] (S. Mho).
as electric-dipole transition (parity selection rule). They can only occur as magnetic-dipole transitions which obey the selection rule DJ ¼ 0; ^1 or as vibronic electric-dipole transitions [12,13]. If there is no inversion symmetry at the site of the rare-earth ion, the uneven crystal field components can mix opposite-parity states into the 4fn configurational levels. The electric-dipole transitions are now no longer strictly forbidden. Transitions with DJ ¼ 0; ^2 are hypersensitive to this effect [12,13]. Emission lines of Eu3þ ion correspond to transitions from the excited 5D0 level to the 7FJ ðJ ¼ 1; 2; …Þ levels of the 4f6 configuration. The theory of forced electric-dipole transitions yields a selection rule in case the initial level has J ¼ 0 [14 – 16]. Transitions to levels with uneven J are forbidden. Further J ¼ 0 to J ¼ 0 is forbidden, because the total orbital momentum does not change. Hence, the transition 5 D0 ! 7F1 presents as magnetic-dipole emission but overruled by the forced electric-dipole emission, and 5D0 ! 7F2 transition is a hypersensitive forced electric-dipole emission. For applications it is required that the main emission is concentrated on the 5D0 ! 7F2 transition around 610– 630 nm [12,13,15,16]. In the emission spectra of Eu3þ in
0038-1098/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 3 8 - 1 0 9 8 ( 0 2 ) 0 0 1 9 5 - 3
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K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
YBO3/Eu3þ or (Y,Gd)BO3/Eu3þ, the magnetic dipole 5 D0 ! 7F1 transition is stronger than the electric dipole 5 D0 ! 7F2 transition, since Eu3þ ions are at centrosymmetric sites [17,18]. The objective of this research is to find red phosphors with excellent color purity by selecting a host lattice, which will supply non-centrosymmetric site for Eu3þ activator. (Y,Gd)Al3(BO3)4 is known to have rhombohedral symmetry with the space group R32, where rare earth ions are at the center of distorted trigonal prism, being in non-centrosymmetric sites [19]. The rare earth ion is situated at the origin with D3 symmetry. The major emission peak for Eu3þ activator in non-centrosymmetric site is the forced electric dipole 5D0 ! 7F2 transition. Hence, Eu3þ ion is doped into (Y,Gd)Al3(BO3)4 lattices pursuing a red phosphor with excellent colorimetric characteristics for PDP applications.
2. Experimental Powder samples of YAl3(BO3)4/Eu3þ, Y0.65Gd0.35Al3 (BO3)4/Eu3þ, and Y0.65Gd0.35BO3/Eu3þ were prepared by the conventional solid state reaction method. Mixtures with proper amounts of Y2O3 (Aldrich 99.9%), Gd2O3 (Aldrich 99.9%), Eu2O3 (Aldrich 99.9%), Al2O3 (Aldrich 99.9%), and H3BO3 (Aldrich 99.5%) were heated at high temperatures. Boric acid added was 120% of the stoichiometric amount. The mixtures were heated in an alumina crucible at 176 8C, which is the melting point for H3BO3, for 10 min before heating at 1150 8C for 8 h. The VUV and UV excitation spectra in the wavelength range of 120– 300 nm were measured at room temperature by a home-built VUV spectrometer, which is composed of a 30 W deuterium lamp (Acton Research Corp., ARC DS775100), a vacuum monochromator (1200 line/nm; f:l: ¼ 200 mm; D21 ¼ 4 nm=mm; ARC VM502), a vacuum sample compartment, and a photomultiplier tube (PMT, ARC DA-780). A high vacuum of 1 £ 1025 Torr was maintained for the excitation monochromator and the sample compartment by a molecular pump (Alcatel, ACT200T). The VUV and UV excitation spectrum was corrected by sodium salicylate, whose quantum efficiency is almost constant in the region [20]. The PL spectra were measured by a spectrofluorometer (Kontron SFM25), which is composed of a 150 W Xe high-pressure arc lamp, two monochromators (1200 line/nm; f:l: ¼ 100 mm; D21 ¼ 8 nm=mmÞ; and a photomultiplier tube (PMT Hamamatsu R928).
3. Results and discussion The VUV excitation spectra of YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ phosphor are shown in Fig. 1(a). The VUV excitation spectrum shows two bands. The one
Fig. 1. The vacuum UV excitation spectra of (a) YAl3(BO3)4/Eu3þ(– –) and Y0.65Gd0.35Al3(BO3)4/Eu3þ (—) phosphors, and (b) Y0.65Gd0.35BO3/Eu3þ.
band in the VUV with the absorption edge at ca. 168 nm is the band-gap absorption of the host lattice (aluminoborate) and the other band at 240 nm is the charge-transfer absorption. Comparing with the excitation spectrum of Y0.65Gd0.35BO3/Eu3þ phosphor (Fig. 1(b)), the position of the VUV band-gap absorption edge for both (Y,Gd)Al3 (BO3)4 and (Y,Gd)BO3 are very similar to each other. On the other hand, the charge-transfer band between Eu3þ ion and O22 ions for (Y,Gd)Al3(BO3)4/Eu3þ is red shifted ca. 20 nm than that for (Y,Gd)BO3/Eu3þ. In the charge-transfer states (CTS), electrons in the neighboring oxygen anions are transferred to a 4f orbital of Eu3þ ion. This process is an allowed transition and results in a strong optical absorption. The energies for CTS are more dependent on their environments, i.e. the host lattices, than those for 4f electron levels [12,13]. Fig. 2 shows the emission spectrum of Y0.65Gd0.35Al3 (BO3)4/Eu3þ along with that of Y0.65Gd0.35BO3/Eu3þ for comparison. There are three emission peaks at 595, 617,
K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
487
Fig. 3. Chromaticity coordinates of YAl3(BO3)4/Eu3þ (A) and Y0.65Gd0.35Al3(BO3)4/Eu3þ (W) along with that of Y0.65Gd0.35BO3/Eu3þ (K) in CIE chromaticity diagram.
Fig. 2. Photoluminescence spectra of (a) Y0.65Gd0.35Al3(BO3)4/Eu3þ obtained with the excitation wavelength of 265 nm and (b) Y0.65Gd0.35BO3/Eu3þ obtained with the excitation wavelength of 242 nm.
and 702 nm, among which the emission peak at 617 nm is the strongest for (Y,Gd)Al3(BO3)4/Eu3þ. The weak emission peak at 595 nm corresponds to the transition from 5D0 level to 7F1 level of Eu3þ ion. The emission peak at 617 nm originated from the electric dipole transition of 5D0 ! 7F2, induced by the lack of inversion symmetry at the Eu3þ site. The choice of host lattices for Eu3þ activator is very important, because the luminescent properties of Eu3þ ion doped phosphors depend to a great extent on the site symmetry occupied by the Eu3þ ion as discussed earlier. Europium ion replaces yttrium ion in both YAl3(BO3)4 and YBO3. The YBO3 orthoborate is known to crystallize in the hexagonal system with P63/m as space group. Y atoms are surrounded by eight oxygen atoms in an arrangement which can be described as a trigonal bicapped antiprism, where yttrium ion is in centrosymmetric sites (having the inversion center) [17, 18]. In the emission spectra of Eu3þ in YBO3/Eu3þ, the
magnetic dipole from 5D0 ! 7F1 transition is stronger than the electric dipole of 5D0 ! 7F2 transition as shown in Fig. 2(b), and the resultant red emission has orangetint whose color coordinates are (0.64, 0.36). As a new host lattice for Eu3þ activator for PDP applications, yttrium aluminoborate YAl3(BO3)4 with trigonal space group R32 adopts the normal trigonal huntite type structure with Y-centered distorted trigonal prisms and Al-centered distorted octahedral dispersed between planes of BO3 triangles that extend parallel to (001). Dissimilar polyhedra share only vertices, resulting in isolation of the YO6 trigonal prisms and BO3 triangles; AlO6 octahedra share edges to form helices extending along [001] [19]. The PL spectrum of (Y,Gd)Al3(BO3)4/ Eu3þ is dominated by the peak at 617 nm due to the forced electric dipole 5D0 ! 7F2 transition of Eu3þ as shown in Fig. 2(a), which is typical of Eu3þ ions occupying non-centrosymmetric sites. (Y,Gd)Al3(BO3)4/ Eu3þ exhibits an excellent purity of red color with CIE chromaticity coordinates of (0.67, 0.33), whereas (Y,Gd)BO3/Eu3þ of (0.64, 0.36) (Fig. 3). Luminescent chromaticity coordinates of the National Television Standard Committee (NTSC) for red are (0.67, 0.33). Hence, YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ phosphors are excellent new red phosphors for PDP applications.
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K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
Acknowledgments This work was partially supported by a grant No. R04-2001-00111 from Korea Science and Engineering Foundation.
References [1] P.N. Yocom, J. Soc. Inf. Display 4 (1996) 149. [2] C. Okazaki, M. Shiiki, T. Suzuki, K. Suzuki, J. Lumin. 87– 89 (2000) 1280. [3] T. Justel, J.-C. Krupa, D.U. Wiechert, J. Lumin. 93 (2001) 179. [4] M. Fukushima, S. Murayama, T. Kaji, S. Mikoshiba, IEEE Trans. Electron Devices ED-22 (1975) 57. [5] A.W. de Jager-Veenis, A. Bril, J. Electrochem. Soc. 123 (1976) 1253. [6] C.R. Ronda, J. Lumin. 72 –74 (1997) 49. [7] J. Koike, T. Kojima, R. Toyonaga, A. Kagami, T. Hase, H. Inaho, J. Electrochem. Soc. 126 (1979) 1008. [8] C.-H. Kim, I.-E. Kwon, C.-H. Park, Y.-J. Hwang, H.-S. Bae,
[9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
B.-Y. Yu, C.-H. Pyun, G.-Y. Hong, J. Alloys Compd. 311 (2000) 33. A. Mayolet, W. Zhang, P. Martin, B. Chassigneux, J.C. Krupa, J. Electrochem. Soc. 143 (1996) 330. H. Yersin, M. Stock, J. Chem. Phys. 76 (1982) 2136. H. Tanino, K. Kobayashi, J. Phys. Soc. Jpn 52 (1983) 1446. G. Blasse, B.C. Grabmaier, Luminescence Materials, Springer-Verlag, New York, 1994, p. 22. S. Shionoya, W.M. Yen, Phosphor Handbook, CRC Press, Boca Raton, 1999, p. 190. S.-I. Mho, J.C. Wright, J. Chem. Phys. 77 (1982) 1183. B.R. Judd, Phys. Rev. 127 (1962) 750. G.S. Ofelt, J. Chem. Phys. 37 (1962) 511. G. Chadeyron, R. Mahiou, M. EL-Ghozzi, A. Arbus, D. Zambon, J.C. Cousseins, J. Lumin. 72–74 (1997) 564. G. Chadeyron, M. EL-Ghozzi, R. Mahiou, A. Arbus, D. Zambon, J.C. Cousseins, J. Solid State Chem. 128 (1997) 261. I. Couwenberg, K. Binnemans, H. Leebeek, C. GorllerWalrand, J. Alloys Compd. 274 (1998) 157. J.A.R. Samson, Techniques of Vacuum Ultraviolet Spectroscopy, Wiley, New York, 1967, p. 216.
Vacuum ultraviolet excitation and photoluminescence characteristics of (Y,Gd)Al3(BO3)4/Eu3þ Kyong-Gue Leea, Byung-Yong Yub, Chong-Hong Pyunb, Sun-Il Mhoa,* a
Department of Molecular Science and Technology, Ajou University, Suwon 442-749, South Korea b Korea Institute of Science and Technology, P.O. Box 131, Seoul 130-650, South Korea Received 4 March 2002; accepted 4 April 2002 by C.N.R. Rao
Abstract Vacuum ultraviolet (VUV) excitation and photoluminescence (PL) characteristics of new red phosphors, YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ are studied. The VUV excitation spectra of both YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ are composed of two broad bands. One band with the absorption edge at ca. 168 nm is the band-gap absorption of aluminoborate and the other broad band centered at 240 nm is the charge transfer transition between Eu3þ and the neighboring oxygen anions. Rare earth ions are at the center of distorted trigonal prism, occupying non-centrosymmetric sites in the orthorhombic YAl3(BO3)4 lattices. The PL spectra of YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ show the strongest emission line at 617 nm due to the forced electric dipole 5D0 ! 7F2 transition of Eu3þ ion, whose luminescent chromaticity coordinates are (0.67, 0.33). q 2002 Elsevier Science Ltd. All rights reserved. PACS: 78.55.2m Keywords: E. Luminescence; C. Point of symmetry of defects
1. Introduction Plasma display panels (PDP) are regarded as the most promising candidates for large sized flat panel displays (FPD) [1 – 4]. Phosphors for the application in PDP are required to have high conversion efficiency by the VUV radiation of 147 and/or 172 nm from the Xe gas plasma [3 – 8]. Refractory oxide compounds with aluminate, silicate, or borate groups have strong absorption in the VUV region [5 – 9]. At present, the most widely used redemitting phosphor for PDP is (Y,Gd)BO3/Eu3þ. The Eu3þ site has inversion symmetry in (Y,Gd)BO3, as in Ba2GdNbO5, NaLuO2, and InBO3, whereas luminescent Eu3þ ions in commercial red phosphors such as YVO4, Y2O3, and Y2O2S occupy the sites that have no inversion symmetry [10,11]. If a rare-earth ion in the crystal lattice occupies a site with inversion symmetry, optical transitions between levels of the 4fn configuration are strictly forbidden * Corresponding author. Tel.: þ82-31-219-2599; fax: þ 82-31219-1615. E-mail address: [email protected] (S. Mho).
as electric-dipole transition (parity selection rule). They can only occur as magnetic-dipole transitions which obey the selection rule DJ ¼ 0; ^1 or as vibronic electric-dipole transitions [12,13]. If there is no inversion symmetry at the site of the rare-earth ion, the uneven crystal field components can mix opposite-parity states into the 4fn configurational levels. The electric-dipole transitions are now no longer strictly forbidden. Transitions with DJ ¼ 0; ^2 are hypersensitive to this effect [12,13]. Emission lines of Eu3þ ion correspond to transitions from the excited 5D0 level to the 7FJ ðJ ¼ 1; 2; …Þ levels of the 4f6 configuration. The theory of forced electric-dipole transitions yields a selection rule in case the initial level has J ¼ 0 [14 – 16]. Transitions to levels with uneven J are forbidden. Further J ¼ 0 to J ¼ 0 is forbidden, because the total orbital momentum does not change. Hence, the transition 5 D0 ! 7F1 presents as magnetic-dipole emission but overruled by the forced electric-dipole emission, and 5D0 ! 7F2 transition is a hypersensitive forced electric-dipole emission. For applications it is required that the main emission is concentrated on the 5D0 ! 7F2 transition around 610– 630 nm [12,13,15,16]. In the emission spectra of Eu3þ in
0038-1098/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 3 8 - 1 0 9 8 ( 0 2 ) 0 0 1 9 5 - 3
486
K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
YBO3/Eu3þ or (Y,Gd)BO3/Eu3þ, the magnetic dipole 5 D0 ! 7F1 transition is stronger than the electric dipole 5 D0 ! 7F2 transition, since Eu3þ ions are at centrosymmetric sites [17,18]. The objective of this research is to find red phosphors with excellent color purity by selecting a host lattice, which will supply non-centrosymmetric site for Eu3þ activator. (Y,Gd)Al3(BO3)4 is known to have rhombohedral symmetry with the space group R32, where rare earth ions are at the center of distorted trigonal prism, being in non-centrosymmetric sites [19]. The rare earth ion is situated at the origin with D3 symmetry. The major emission peak for Eu3þ activator in non-centrosymmetric site is the forced electric dipole 5D0 ! 7F2 transition. Hence, Eu3þ ion is doped into (Y,Gd)Al3(BO3)4 lattices pursuing a red phosphor with excellent colorimetric characteristics for PDP applications.
2. Experimental Powder samples of YAl3(BO3)4/Eu3þ, Y0.65Gd0.35Al3 (BO3)4/Eu3þ, and Y0.65Gd0.35BO3/Eu3þ were prepared by the conventional solid state reaction method. Mixtures with proper amounts of Y2O3 (Aldrich 99.9%), Gd2O3 (Aldrich 99.9%), Eu2O3 (Aldrich 99.9%), Al2O3 (Aldrich 99.9%), and H3BO3 (Aldrich 99.5%) were heated at high temperatures. Boric acid added was 120% of the stoichiometric amount. The mixtures were heated in an alumina crucible at 176 8C, which is the melting point for H3BO3, for 10 min before heating at 1150 8C for 8 h. The VUV and UV excitation spectra in the wavelength range of 120– 300 nm were measured at room temperature by a home-built VUV spectrometer, which is composed of a 30 W deuterium lamp (Acton Research Corp., ARC DS775100), a vacuum monochromator (1200 line/nm; f:l: ¼ 200 mm; D21 ¼ 4 nm=mm; ARC VM502), a vacuum sample compartment, and a photomultiplier tube (PMT, ARC DA-780). A high vacuum of 1 £ 1025 Torr was maintained for the excitation monochromator and the sample compartment by a molecular pump (Alcatel, ACT200T). The VUV and UV excitation spectrum was corrected by sodium salicylate, whose quantum efficiency is almost constant in the region [20]. The PL spectra were measured by a spectrofluorometer (Kontron SFM25), which is composed of a 150 W Xe high-pressure arc lamp, two monochromators (1200 line/nm; f:l: ¼ 100 mm; D21 ¼ 8 nm=mmÞ; and a photomultiplier tube (PMT Hamamatsu R928).
3. Results and discussion The VUV excitation spectra of YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ phosphor are shown in Fig. 1(a). The VUV excitation spectrum shows two bands. The one
Fig. 1. The vacuum UV excitation spectra of (a) YAl3(BO3)4/Eu3þ(– –) and Y0.65Gd0.35Al3(BO3)4/Eu3þ (—) phosphors, and (b) Y0.65Gd0.35BO3/Eu3þ.
band in the VUV with the absorption edge at ca. 168 nm is the band-gap absorption of the host lattice (aluminoborate) and the other band at 240 nm is the charge-transfer absorption. Comparing with the excitation spectrum of Y0.65Gd0.35BO3/Eu3þ phosphor (Fig. 1(b)), the position of the VUV band-gap absorption edge for both (Y,Gd)Al3 (BO3)4 and (Y,Gd)BO3 are very similar to each other. On the other hand, the charge-transfer band between Eu3þ ion and O22 ions for (Y,Gd)Al3(BO3)4/Eu3þ is red shifted ca. 20 nm than that for (Y,Gd)BO3/Eu3þ. In the charge-transfer states (CTS), electrons in the neighboring oxygen anions are transferred to a 4f orbital of Eu3þ ion. This process is an allowed transition and results in a strong optical absorption. The energies for CTS are more dependent on their environments, i.e. the host lattices, than those for 4f electron levels [12,13]. Fig. 2 shows the emission spectrum of Y0.65Gd0.35Al3 (BO3)4/Eu3þ along with that of Y0.65Gd0.35BO3/Eu3þ for comparison. There are three emission peaks at 595, 617,
K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
487
Fig. 3. Chromaticity coordinates of YAl3(BO3)4/Eu3þ (A) and Y0.65Gd0.35Al3(BO3)4/Eu3þ (W) along with that of Y0.65Gd0.35BO3/Eu3þ (K) in CIE chromaticity diagram.
Fig. 2. Photoluminescence spectra of (a) Y0.65Gd0.35Al3(BO3)4/Eu3þ obtained with the excitation wavelength of 265 nm and (b) Y0.65Gd0.35BO3/Eu3þ obtained with the excitation wavelength of 242 nm.
and 702 nm, among which the emission peak at 617 nm is the strongest for (Y,Gd)Al3(BO3)4/Eu3þ. The weak emission peak at 595 nm corresponds to the transition from 5D0 level to 7F1 level of Eu3þ ion. The emission peak at 617 nm originated from the electric dipole transition of 5D0 ! 7F2, induced by the lack of inversion symmetry at the Eu3þ site. The choice of host lattices for Eu3þ activator is very important, because the luminescent properties of Eu3þ ion doped phosphors depend to a great extent on the site symmetry occupied by the Eu3þ ion as discussed earlier. Europium ion replaces yttrium ion in both YAl3(BO3)4 and YBO3. The YBO3 orthoborate is known to crystallize in the hexagonal system with P63/m as space group. Y atoms are surrounded by eight oxygen atoms in an arrangement which can be described as a trigonal bicapped antiprism, where yttrium ion is in centrosymmetric sites (having the inversion center) [17, 18]. In the emission spectra of Eu3þ in YBO3/Eu3þ, the
magnetic dipole from 5D0 ! 7F1 transition is stronger than the electric dipole of 5D0 ! 7F2 transition as shown in Fig. 2(b), and the resultant red emission has orangetint whose color coordinates are (0.64, 0.36). As a new host lattice for Eu3þ activator for PDP applications, yttrium aluminoborate YAl3(BO3)4 with trigonal space group R32 adopts the normal trigonal huntite type structure with Y-centered distorted trigonal prisms and Al-centered distorted octahedral dispersed between planes of BO3 triangles that extend parallel to (001). Dissimilar polyhedra share only vertices, resulting in isolation of the YO6 trigonal prisms and BO3 triangles; AlO6 octahedra share edges to form helices extending along [001] [19]. The PL spectrum of (Y,Gd)Al3(BO3)4/ Eu3þ is dominated by the peak at 617 nm due to the forced electric dipole 5D0 ! 7F2 transition of Eu3þ as shown in Fig. 2(a), which is typical of Eu3þ ions occupying non-centrosymmetric sites. (Y,Gd)Al3(BO3)4/ Eu3þ exhibits an excellent purity of red color with CIE chromaticity coordinates of (0.67, 0.33), whereas (Y,Gd)BO3/Eu3þ of (0.64, 0.36) (Fig. 3). Luminescent chromaticity coordinates of the National Television Standard Committee (NTSC) for red are (0.67, 0.33). Hence, YAl3(BO3)4/Eu3þ and Y0.65Gd0.35Al3(BO3)4/Eu3þ phosphors are excellent new red phosphors for PDP applications.
488
K.-G. Lee et al. / Solid State Communications 122 (2002) 485–488
Acknowledgments This work was partially supported by a grant No. R04-2001-00111 from Korea Science and Engineering Foundation.
References [1] P.N. Yocom, J. Soc. Inf. Display 4 (1996) 149. [2] C. Okazaki, M. Shiiki, T. Suzuki, K. Suzuki, J. Lumin. 87– 89 (2000) 1280. [3] T. Justel, J.-C. Krupa, D.U. Wiechert, J. Lumin. 93 (2001) 179. [4] M. Fukushima, S. Murayama, T. Kaji, S. Mikoshiba, IEEE Trans. Electron Devices ED-22 (1975) 57. [5] A.W. de Jager-Veenis, A. Bril, J. Electrochem. Soc. 123 (1976) 1253. [6] C.R. Ronda, J. Lumin. 72 –74 (1997) 49. [7] J. Koike, T. Kojima, R. Toyonaga, A. Kagami, T. Hase, H. Inaho, J. Electrochem. Soc. 126 (1979) 1008. [8] C.-H. Kim, I.-E. Kwon, C.-H. Park, Y.-J. Hwang, H.-S. Bae,
[9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
B.-Y. Yu, C.-H. Pyun, G.-Y. Hong, J. Alloys Compd. 311 (2000) 33. A. Mayolet, W. Zhang, P. Martin, B. Chassigneux, J.C. Krupa, J. Electrochem. Soc. 143 (1996) 330. H. Yersin, M. Stock, J. Chem. Phys. 76 (1982) 2136. H. Tanino, K. Kobayashi, J. Phys. Soc. Jpn 52 (1983) 1446. G. Blasse, B.C. Grabmaier, Luminescence Materials, Springer-Verlag, New York, 1994, p. 22. S. Shionoya, W.M. Yen, Phosphor Handbook, CRC Press, Boca Raton, 1999, p. 190. S.-I. Mho, J.C. Wright, J. Chem. Phys. 77 (1982) 1183. B.R. Judd, Phys. Rev. 127 (1962) 750. G.S. Ofelt, J. Chem. Phys. 37 (1962) 511. G. Chadeyron, R. Mahiou, M. EL-Ghozzi, A. Arbus, D. Zambon, J.C. Cousseins, J. Lumin. 72–74 (1997) 564. G. Chadeyron, M. EL-Ghozzi, R. Mahiou, A. Arbus, D. Zambon, J.C. Cousseins, J. Solid State Chem. 128 (1997) 261. I. Couwenberg, K. Binnemans, H. Leebeek, C. GorllerWalrand, J. Alloys Compd. 274 (1998) 157. J.A.R. Samson, Techniques of Vacuum Ultraviolet Spectroscopy, Wiley, New York, 1967, p. 216.