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Fluorescence spectra of Tm3+-doped rare earth oxychloride powder phosphors
ELSEVIER
Materials Chemistry and Physics 43 (1996) 195-198
Materials
Science Communication
Fluorescence spectra of Tm 3+-doped rare earth oxychloride powder phosphors U. Rambabu, T. Balaji, K. Annapurna, Department
of Physics,
Sri
Venkateswara
Uniuersity,
Tirupati
S. Buddhudu* 517 502, India
Received 9 January 1995;revised 24 May 1995;accepted 26 May 1995
Abstract
This paper reports the fluorescenceproperties of a new family of Tm 3+-dopedpowder phosphorsof LaOCl, GdOCI, YOCl, (La,Gd) OCl, (La,Y) OCl and (Gd,Y) OCl. A bright blue emission( ‘D, --f 3F4)was observedfrom all thesephosphorsunder a UV lamp and this situation was confirmed by fitting the colour coordinates(2, 7) in the IEC chromaticity diagram. The relative fluorescenceintensity ratios (R) for the different measuredemissionlevelswere alsoevaluatedin order to examinethe host matrix compositional effects on the fluorescencebehaviours. For the measuredfluorescenttransitions, the stimulated emissioncross sections(orE) were also computed. Keywords:
Fluorescence spectra;Powderphosphors; Rareearthoxychlorides
1. Introduction
cence phenomenon from the europium dopant ion [7,8]. Both the excitation and the photoluminescence spectra
Over the past four years, the authors have been involved in the production and analysis of a variety of powder phosphors for their use in CRT and Colour-TV
monitors [l-5]. Now, it is of interest to look upon yet another new set of phosphors doped with the Tm3+ for their fluorescence characterization,
2. Experimental
By employing the procedures given by Fidancev et al. [6], the following six Tm 3+-doped powder phosphors have been prepared with CaCl, as the flux at 700 “C in air: (a) LaOCl (b) GdOCl (c) YOCl
(4 (LacdddOC1 (e> (Lao.JdOC1 (0 (Gdos>Yos)OC1 These compositions have earlier been identified as the suitable host combinations, to observe better the fluores-
5
t
380
Wavelength
* Corresponding author. 0254-0584/96/$15.00 0 1996ElsevierScience S.A. All rightsreserved SSDIO2_5_4-0584(95)01616-3
t
260 (nm 1
Fig. 1. Excitationspectrumof Tm3+-doped LaOCl.
196
U. Rambabu
540
460
540
et al. /Materials
460
540
Chemistry
460
Wavelength
and Physics
540
460
43 (1996)
540
195-198
460
540
460
(nm)
Fig. 2. Photoluminescence spectra of Tm 3+-doped: (a) LaOCl; (b) GdOCl; (c) YOCl; (d) (La, Gd)OCI; (e) (La, Y)OCI; and (f) (Gd, Y)OCl powder phosphors (A,,, = 359 nm).
of these Tm3+-doped powder phosphors have been recorded on a Hitachi 650-10s spectrofluoremeter using a 150 W xenon arc lamp as the excitation source (the authors had access to this facility at the Phosphors Laboratory, CECRI, Karaikudi). The recorded excitation spectrum of a Tm3’:phosphor [A,,,: 359 nm (‘DJ] is shown in Fig. 1. With this excitation line, the photoluminescence spectra of all six Tm3’:powder phosphors have been recorded in the visible range of 420-540 nm and are shown in Fig. 2(a)-(f).
Table 1 Relative fluorescence intensity ratios (R) of Tm3+:powder Emission transition ratios
[
‘G4 -+ ‘D, + 3H,
1
[ 1Gq+3Hg 1Gq-‘3Hg 1 [ ‘G4 ‘D, +--t3Fq 3H, 1
3. Results and discussion From the recorded photoluminescenbe ‘spectra of the Tm3+:powder phosphors, the following emission transitions have been identified based on Ref. [ 91: ID, --f 3HS [510-530 nm]; 1Gq+3Hg [470-490 nm]; ‘Dz_t3Fq [450-460 nm]; 3P,, +3H4 [430-440 nm]. In order to compare the fluorescence efficiencies of the six powder phosphors prepared, we have estimated the relative intensity ratios (R) pertaining to
phosphors
LaOCl
GdOCl
YOGI
(La, Gd)OCl
(La, Y)OCl
(Gd, Y)OCI
0.12 0.25 0.37
0.13 0.33 0.66
0.14 0.28 0.57
0.21
0.14 0.28 0.42
0.14
0.28 0.35
0.87 1.00 0.65
0.86 1.00 0.73
1.07 1.0 1.0
0.57 1.00 0.71
0.85 1.00 0.71
0.85
1.56 8.87
8.40 1.46
2.35 1.92 0.64
1.64 6.57 0.71
1.78 6.0 0.64
1.57 8.42 0.71
0.56
0.66
0.62
0.73
1.0
0.71
0.78
0.85
0.28 0.50 1.00
0.78
U. Ranzbabu
et al. /Materials
Chemistry
and Physics
43 (1996)
Table 2 Colour coordinates (2, p) of Tm3+-doped powder phosphors Phosphor
x
r;
LaOCl GdOCl YOGI (La, Gd)OCl (La, Y)OCl (Gd, Y)OCl
0.1474 0.1454 0.1442 0.1429 0.1398 0.1380
0.1330 0.0777 0.1054 0.2030 0.1801 0.1953
195-195
197
0.8
0
the emission levels and the results are presented in Table 1. From this table it is clearer to see that a particular phosphors, namely Tm3+:LaOC1 shows brighter luminescent intensities in its spectral profiles than the other different materials studied. Following the standard procedures, the authors have computed the colour coordinates (X, P) for the Tm3’:powder phosphors based on the features of the recorded fluorescence spectra and the data are given in Table 2. The magnitudes of coordinates (X, 7) for Tm”+:phosphors in the present study are satisfactorily coincident with the earlier reported results for other types of Tm3+:phosphors [lo]. Fig. 3 describes the CIE chromaticity diagram comprising the three primary colours (blue, green, red) on which the measured colour coordinates (2, P) are superimposed to verify the validity of the results, to see that our data are the recommended values of the colour coordinates. From this diagram (Fig. 3) it is noticed that all the phosphors characterized would properly be fitted in the blue colour coordinate region well within (the shaded portion). In addition to these calculations, the authors have also evaluated the stimulated emission cross sections (a;) for the measured emission transitions of the Tm3+:phosphors. The squared reduced matrix element
0.2 Ok 0.6 X-COOfUinate
0.8
Fig. 3. CIE chromaticity diagram.
I/ v/j2 values used for the evaluation of transition probabilities (A s-‘) in the present work are readily available in Ref. [ 111. The calculated transition probabilities (A s-l), measured emission level peak positions (n, nm), half band widths (A& nm) and stimulated emission cross sections (G,” cm2) for emission levels of the phosphors studied here are listed in Table 3 in order to have an insight into the compositional effects on them. Finally, based on the results obtained from the fluorescence spectra, it becomes possible to suggest that amongst the six Tm3’:phosphors, the Tm3+:LaOC1 phosphor could be declared as a more promising and ideal material for observing a bright blue colour emission from the monitors of the electronic devices such as CRT and colour televisions.
Acknowledgements The authors express grateful thanks to Professor S.V.J. Lakshman for his kind co-operation and support in the present work. Two of the authors (TB and KA)
Table 3 Transition probabilities (A s-l), emission level peak positions (,$ nm), half band widths (A?., nm) and stimulated emission cross sections (CT: x 10w2’ cm’) of Tm 3+-doped powder phosphors Emission transition
A (s-l)
GdOCl
‘D2-t3HS
1066
503 512 525
4 4 2
12.78 1.37 3.03
505 515 526
4 3 6
1.29 505 1.86 515 1.01 525
4 3 4
1.29 502 1.86 512 1.49 527
6 4 4
0.83 505 1.35 510 1.35 525
6 4 4
0.86 1.33 1.51
505 515 525
6 4 4
0.86 1.39 1.51
‘G,-t3H6
5053
470 477 490
2 6 5
9.22 3.26 9.27
470 480 490
5 5 2
3.63 490 4.01 480 10.79 470
4 4 2
5.39 490 5.01 476 9.08 470
4 5 2
5.39 3.86 9.08
490 480 470
4 4 2
5.34 5.01 9.08
490 480 470
4 4 2
5.34 5.01 9.08
‘D, -+ 3F,
45618
465 455 450
3 2 2
52.42 73.50 70.08
465 456 450
2 2 2
78.63 73.91 70.08
466 455 450
3 3 2
53.56 48.84 70.08
465 455 450
2 3 2
78.63 48.84 70.08
465 455 450
2 3 2
78.63 48.84 70.08
466 455 450
2 2 2
80.34 73.50 70.08
3Po--) 3H,
13640
437
6
6.13
439
6
6.39
439
6
6.30
436
6
6.13
438
6
6.13
438
6
6.30
LaOCl
YOCl
(La, Gd)OCl
(La, Y)OCl
(Gd, Y)OCl
198
U. Rambabu
et al. /Materials
would like to thank the CSIR, New Delhi, award of Senior Research Fellowships.
Chemistry
for the
References [l] [2] [3] [4] [5] [6]
T. Balaji and S. Buddhudu, Spectrosc. Lett., 26 (1993) 113. T. Balaji and S. Buddhudu, Mater. Chem. Phys., 36 (1993) 194. T. Balaji and S. Buddhudu, Spectrochim. Acta, 49A (1993) 1029. T. Balaji and S. Buddhudu, Spectrochim. Acta, 49A (1993) 1817. T. Balaji and S. Buddhudu, J. Mater. Sci. Lett., 12 (1993) 1002. E.A. Fidancev, M. Lemaitre, P. Percher and J. Holsa, in Xu Guangxian (ed.), Evaluation of Crystal Field Effects in REOCI
and Physics
43 (1996)
195-198
Series in Rare-Earth Development alld Application, Vol. 1, International Academic, ROC, 1991, p. 95. [7] D.M. De Leeuw, C.A.H.A. Mutsaers, H. Mulder and D.B.M. Kladssen, J. Electrochem. Sot., 135 (1988) 1009. [S] U. Rambabu, T. Balaji and S. Buddhudu, Mater. Res. BUN., 30 (1995) 891. [9] C. Li, A. Lagriffoul, R. Moncorge, J.C. Souriau, C. Bore1 and Cl. Wyon, J. Lumiu., 62 (1994) 157. [lo] Li Chang-hua et al., in S.U. Qiang (ed.), Rare Earth Spectroscopy, Vol. 2, World Scientific, Singapore, 1990, p. 125. [ 111 N. Spector, R. Reisfild and C. Boehm, Chem. Phys. Mt., 49 (1977) 49.
Materials Chemistry and Physics 43 (1996) 195-198
Materials
Science Communication
Fluorescence spectra of Tm 3+-doped rare earth oxychloride powder phosphors U. Rambabu, T. Balaji, K. Annapurna, Department
of Physics,
Sri
Venkateswara
Uniuersity,
Tirupati
S. Buddhudu* 517 502, India
Received 9 January 1995;revised 24 May 1995;accepted 26 May 1995
Abstract
This paper reports the fluorescenceproperties of a new family of Tm 3+-dopedpowder phosphorsof LaOCl, GdOCI, YOCl, (La,Gd) OCl, (La,Y) OCl and (Gd,Y) OCl. A bright blue emission( ‘D, --f 3F4)was observedfrom all thesephosphorsunder a UV lamp and this situation was confirmed by fitting the colour coordinates(2, 7) in the IEC chromaticity diagram. The relative fluorescenceintensity ratios (R) for the different measuredemissionlevelswere alsoevaluatedin order to examinethe host matrix compositional effects on the fluorescencebehaviours. For the measuredfluorescenttransitions, the stimulated emissioncross sections(orE) were also computed. Keywords:
Fluorescence spectra;Powderphosphors; Rareearthoxychlorides
1. Introduction
cence phenomenon from the europium dopant ion [7,8]. Both the excitation and the photoluminescence spectra
Over the past four years, the authors have been involved in the production and analysis of a variety of powder phosphors for their use in CRT and Colour-TV
monitors [l-5]. Now, it is of interest to look upon yet another new set of phosphors doped with the Tm3+ for their fluorescence characterization,
2. Experimental
By employing the procedures given by Fidancev et al. [6], the following six Tm 3+-doped powder phosphors have been prepared with CaCl, as the flux at 700 “C in air: (a) LaOCl (b) GdOCl (c) YOCl
(4 (LacdddOC1 (e> (Lao.JdOC1 (0 (Gdos>Yos)OC1 These compositions have earlier been identified as the suitable host combinations, to observe better the fluores-
5
t
380
Wavelength
* Corresponding author. 0254-0584/96/$15.00 0 1996ElsevierScience S.A. All rightsreserved SSDIO2_5_4-0584(95)01616-3
t
260 (nm 1
Fig. 1. Excitationspectrumof Tm3+-doped LaOCl.
196
U. Rambabu
540
460
540
et al. /Materials
460
540
Chemistry
460
Wavelength
and Physics
540
460
43 (1996)
540
195-198
460
540
460
(nm)
Fig. 2. Photoluminescence spectra of Tm 3+-doped: (a) LaOCl; (b) GdOCl; (c) YOCl; (d) (La, Gd)OCI; (e) (La, Y)OCI; and (f) (Gd, Y)OCl powder phosphors (A,,, = 359 nm).
of these Tm3+-doped powder phosphors have been recorded on a Hitachi 650-10s spectrofluoremeter using a 150 W xenon arc lamp as the excitation source (the authors had access to this facility at the Phosphors Laboratory, CECRI, Karaikudi). The recorded excitation spectrum of a Tm3’:phosphor [A,,,: 359 nm (‘DJ] is shown in Fig. 1. With this excitation line, the photoluminescence spectra of all six Tm3’:powder phosphors have been recorded in the visible range of 420-540 nm and are shown in Fig. 2(a)-(f).
Table 1 Relative fluorescence intensity ratios (R) of Tm3+:powder Emission transition ratios
[
‘G4 -+ ‘D, + 3H,
1
[ 1Gq+3Hg 1Gq-‘3Hg 1 [ ‘G4 ‘D, +--t3Fq 3H, 1
3. Results and discussion From the recorded photoluminescenbe ‘spectra of the Tm3+:powder phosphors, the following emission transitions have been identified based on Ref. [ 91: ID, --f 3HS [510-530 nm]; 1Gq+3Hg [470-490 nm]; ‘Dz_t3Fq [450-460 nm]; 3P,, +3H4 [430-440 nm]. In order to compare the fluorescence efficiencies of the six powder phosphors prepared, we have estimated the relative intensity ratios (R) pertaining to
phosphors
LaOCl
GdOCl
YOGI
(La, Gd)OCl
(La, Y)OCl
(Gd, Y)OCI
0.12 0.25 0.37
0.13 0.33 0.66
0.14 0.28 0.57
0.21
0.14 0.28 0.42
0.14
0.28 0.35
0.87 1.00 0.65
0.86 1.00 0.73
1.07 1.0 1.0
0.57 1.00 0.71
0.85 1.00 0.71
0.85
1.56 8.87
8.40 1.46
2.35 1.92 0.64
1.64 6.57 0.71
1.78 6.0 0.64
1.57 8.42 0.71
0.56
0.66
0.62
0.73
1.0
0.71
0.78
0.85
0.28 0.50 1.00
0.78
U. Ranzbabu
et al. /Materials
Chemistry
and Physics
43 (1996)
Table 2 Colour coordinates (2, p) of Tm3+-doped powder phosphors Phosphor
x
r;
LaOCl GdOCl YOGI (La, Gd)OCl (La, Y)OCl (Gd, Y)OCl
0.1474 0.1454 0.1442 0.1429 0.1398 0.1380
0.1330 0.0777 0.1054 0.2030 0.1801 0.1953
195-195
197
0.8
0
the emission levels and the results are presented in Table 1. From this table it is clearer to see that a particular phosphors, namely Tm3+:LaOC1 shows brighter luminescent intensities in its spectral profiles than the other different materials studied. Following the standard procedures, the authors have computed the colour coordinates (X, P) for the Tm3’:powder phosphors based on the features of the recorded fluorescence spectra and the data are given in Table 2. The magnitudes of coordinates (X, 7) for Tm”+:phosphors in the present study are satisfactorily coincident with the earlier reported results for other types of Tm3+:phosphors [lo]. Fig. 3 describes the CIE chromaticity diagram comprising the three primary colours (blue, green, red) on which the measured colour coordinates (2, P) are superimposed to verify the validity of the results, to see that our data are the recommended values of the colour coordinates. From this diagram (Fig. 3) it is noticed that all the phosphors characterized would properly be fitted in the blue colour coordinate region well within (the shaded portion). In addition to these calculations, the authors have also evaluated the stimulated emission cross sections (a;) for the measured emission transitions of the Tm3+:phosphors. The squared reduced matrix element
0.2 Ok 0.6 X-COOfUinate
0.8
Fig. 3. CIE chromaticity diagram.
I/ v/j2 values used for the evaluation of transition probabilities (A s-‘) in the present work are readily available in Ref. [ 111. The calculated transition probabilities (A s-l), measured emission level peak positions (n, nm), half band widths (A& nm) and stimulated emission cross sections (G,” cm2) for emission levels of the phosphors studied here are listed in Table 3 in order to have an insight into the compositional effects on them. Finally, based on the results obtained from the fluorescence spectra, it becomes possible to suggest that amongst the six Tm3’:phosphors, the Tm3+:LaOC1 phosphor could be declared as a more promising and ideal material for observing a bright blue colour emission from the monitors of the electronic devices such as CRT and colour televisions.
Acknowledgements The authors express grateful thanks to Professor S.V.J. Lakshman for his kind co-operation and support in the present work. Two of the authors (TB and KA)
Table 3 Transition probabilities (A s-l), emission level peak positions (,$ nm), half band widths (A?., nm) and stimulated emission cross sections (CT: x 10w2’ cm’) of Tm 3+-doped powder phosphors Emission transition
A (s-l)
GdOCl
‘D2-t3HS
1066
503 512 525
4 4 2
12.78 1.37 3.03
505 515 526
4 3 6
1.29 505 1.86 515 1.01 525
4 3 4
1.29 502 1.86 512 1.49 527
6 4 4
0.83 505 1.35 510 1.35 525
6 4 4
0.86 1.33 1.51
505 515 525
6 4 4
0.86 1.39 1.51
‘G,-t3H6
5053
470 477 490
2 6 5
9.22 3.26 9.27
470 480 490
5 5 2
3.63 490 4.01 480 10.79 470
4 4 2
5.39 490 5.01 476 9.08 470
4 5 2
5.39 3.86 9.08
490 480 470
4 4 2
5.34 5.01 9.08
490 480 470
4 4 2
5.34 5.01 9.08
‘D, -+ 3F,
45618
465 455 450
3 2 2
52.42 73.50 70.08
465 456 450
2 2 2
78.63 73.91 70.08
466 455 450
3 3 2
53.56 48.84 70.08
465 455 450
2 3 2
78.63 48.84 70.08
465 455 450
2 3 2
78.63 48.84 70.08
466 455 450
2 2 2
80.34 73.50 70.08
3Po--) 3H,
13640
437
6
6.13
439
6
6.39
439
6
6.30
436
6
6.13
438
6
6.13
438
6
6.30
LaOCl
YOCl
(La, Gd)OCl
(La, Y)OCl
(Gd, Y)OCl
198
U. Rambabu
et al. /Materials
would like to thank the CSIR, New Delhi, award of Senior Research Fellowships.
Chemistry
for the
References [l] [2] [3] [4] [5] [6]
T. Balaji and S. Buddhudu, Spectrosc. Lett., 26 (1993) 113. T. Balaji and S. Buddhudu, Mater. Chem. Phys., 36 (1993) 194. T. Balaji and S. Buddhudu, Spectrochim. Acta, 49A (1993) 1029. T. Balaji and S. Buddhudu, Spectrochim. Acta, 49A (1993) 1817. T. Balaji and S. Buddhudu, J. Mater. Sci. Lett., 12 (1993) 1002. E.A. Fidancev, M. Lemaitre, P. Percher and J. Holsa, in Xu Guangxian (ed.), Evaluation of Crystal Field Effects in REOCI
and Physics
43 (1996)
195-198
Series in Rare-Earth Development alld Application, Vol. 1, International Academic, ROC, 1991, p. 95. [7] D.M. De Leeuw, C.A.H.A. Mutsaers, H. Mulder and D.B.M. Kladssen, J. Electrochem. Sot., 135 (1988) 1009. [S] U. Rambabu, T. Balaji and S. Buddhudu, Mater. Res. BUN., 30 (1995) 891. [9] C. Li, A. Lagriffoul, R. Moncorge, J.C. Souriau, C. Bore1 and Cl. Wyon, J. Lumiu., 62 (1994) 157. [lo] Li Chang-hua et al., in S.U. Qiang (ed.), Rare Earth Spectroscopy, Vol. 2, World Scientific, Singapore, 1990, p. 125. [ 111 N. Spector, R. Reisfild and C. Boehm, Chem. Phys. Mt., 49 (1977) 49.