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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 25 — Dec. 10, 2007
  • pp: 16980–16985
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Tunable luminescence of CaO-Al2O3-GeO2 glasses

Geng Lin, Bin Zhu, Shifeng Zhou, Hucheng Yang, and Jianrong Qiu  »View Author Affiliations


Optics Express, Vol. 15, Issue 25, pp. 16980-16985 (2007)
http://dx.doi.org/10.1364/OE.15.016980


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Abstract

We report tunable luminescence in oxygen-deficient CaO-Al2O3-GeO2 glasses. The glass samples were prepared by adding metal Al instead of corresponding oxide (Al2O3). Efficient blue and red emissions were observed when excited by 300 and 370 nm ultraviolet light, respectively. By adjusting the content of metal Al, we could control the quantities of the defects which results in tunable luminescence from blue to white to red. Furthermore the resultant oxygen-deficient glasses have shown bright white luminescence when the excitation wavelength tuned to 335nm. Our method opens a new route for the white light illumination.

© 2007 Optical Society of America

1. Introduction

CaO-Al2O3-GeO2 glasses show good mechanical strength and chemical durability [10

10. M. C. Wang, J. S. Wang, and M. H. Hon, “Effect of Na2O addition on the optical properties and chemical durability of Li2O-CaO-Al2O3-GeO2 glass,” Jpn. J. Appl. Phys. 33, 2651–2655 (1994). [CrossRef]

,11

11. L. Huang, X. Liu, W. Xu, B. Chen, and J. Lin, “Infrared and visible luminescence properties of Er3+ and Yb3+ ions codoped Ca3Al2Ge3O12 glass under 978 nm diode laser excitation,” J. Appl. Phys. 90, 5550–5553 (2001). [CrossRef]

]. They are transparent from visible to infrared wavelength region, and have applications as infrared window and sensor. However, there have been few investigations on the defect formation in these glasses. Here, we report a simple method to control oxygen-deficient defects in CaO-Al2O3-GeO2 glasses by adding metal Al instead of corresponding oxide (Al2O3). We observed tunable luminescence from blue to white to red from the glass samples when excited by ultraviolet (UV) light. The glasses may be useful as colorless and transparent fluorescent materials, such as for lamps, displays, and white LED lighting [12

12. S. Sivakumar, F. C. J. M. van Veggel, and M. Raudsepp, “Bright white light through up-conversion of a single NIR source from sol-gel-derived thin film made with Ln3+-doped LaF3 nanoparticles,” J. Am. Chem. Soc. 127, 12464–12465 (2005). [CrossRef] [PubMed]

,13

13. M. J. Bowers II, J. R. McBride, and S. J. Rosenthal, “White-light emission from magic-sized cadmium selenide nanocrystals,” J. Am. Chem. Soc. 127, 15378–15379 (2005). [CrossRef]

].

2. Experiment

The glass composition was 40CaO-30Al2O3-30GeO2 (mol%). In order to prepare oxygen-deficient glass samples, a part of Al2O3 was substituted by Al. The glass samples without Al, using Al instead of 1, 2, 3, 5, 10mol% Al2O3 are referred to samples A, B, C, D, E and F, respectively. The raw materials were reagent-grade CaCO3, Al2O3, GeO2 and Al. Approximately 30 g batches were mixed and then melted in alumina crucibles with alumina caps at 1550°C for 1h under the ambient atmosphere. The melts were poured onto a stainless plate and pressed with another stainless plate to obtain glass plates. All of the obtained glasses were transparent. The glass samples were cut, polished and subjected to optical measurement. The absorption spectra of the samples were measured by a spectrophotometer (Hitachi-4100). The photoluminescence and excitation spectra were measured with a fluorescence spectrometer (Hitachi-4500), and the luminescence photographs of glass samples were excited by a Xe lamp in the spectrophotometer. Electron spin resonance (ESR) spectra were obtained using a JEOL JES-FA200 ESR spectrometer (300 K, 9.063 GHz, X-band). All of the measurements were carried out at room temperature.

3. Results and discussion

Fig. 1. Absorption spectra of CaO-Al2O3-SiO2 glasses. a, b, c, d, e, and f are absorption spectra of glass samples A, B, C, D, E, and F, respectively.

Figure 1 shows the absorption spectra of CaO-Al2O3-SiO2 glass samples. When Al was added instead of part Al2O3 in the glass, it was observed that the absorption edge shifts to the shorter wavelength at first and then to longer wavelength with increasing Al content. When using Al instead of part Al2O3 as glass composition, oxygen content decreases in the network, and Al enters the glass network through combing with NBO for Al have strong reducibility, the process can be proposed as follows:

NBO+AlAl-BO

GeO 4+AlGe 2++O--Al-O -(NBO)

Fig. 2. ESR spectra of CaO-Al2O3-GeO2 glasses, (a): sample A; (b): sample D; (c): sample F.

ESR spectra of the glass samples are shown in Fig. 2. No ESR signal was observed in sample A. When Al added, an apparent ESR signal appeared at g=1.994. This signal is due to the germanium oxygen deficient centers (GODCs) [3

3. H. Hosono, Y. Abe, D. L. Kinser, R. A. Weeks, K. Muta, and H. Kawazoe, “Nature and origin of the 5-eV band in SiO2:GeO2 glasses,” Phys. Rev. B 46, 11 445-11 451 (1992). [CrossRef]

,15

15. M. Fujimaki, T. Watanabe, T. Katoh, T. Kasahara, N. Miyazaki, Y. Ohki, and H. Nishikawa, “Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings,” Phys. Rev. B 60, 4682–4687 (1999). [CrossRef]

].

Fig. 3. Photographs of the emission states of glass samples when excited by UV lights, a, b, c, d, e, and f are glass samples A, B, C, D, E and F, respectively. The excitation wavelengths for blue, white, and red emissions are 300, 335 and 370nm, respectively.

Figure 3 shows photographs of the emission states of glass samples excited by UV lights. No emission was observed in sample A. For the Al added samples we observed bright blue, white, and red emissions when excited by 300, 335 and 370nm, respectively.

Fig. 4. Photoluminescence (right) and excitation (left) spectra of glass samples, a, b, c, d, e and f are referred to glass samples A, B, C, D, E, and F, respectively. The excitation wavelengths of A, B, and C are 300, 335 and 370nm, respectively.

The photoluminescence and excitation spectra of glass samples are shown in Fig. 4. No PL bands were observed in sample A. In the Al added samples, blue light emission with two broad bands centered at 375 and 460nm; white emission with two broad bands centered at 400 and 510nm; and red light emission with two broad bands centered at 460 and 630 nm were observed when excited by 300, 335 and 370 nm UV lights. We choose the sample F to study the complex behavior based on the time-resolved PL spectra (Fig. 5). When excited by 300nm UV light, the sample only shows a broad band at 460nm, the band centered at 375nm disappeared for the lifetime of the 375nm band is 11µs and the shortest delay of time-resolved PL experiment was 10µs. When excited by 335nm UV light, it shows four PL bands at 405, 510, 630 and 680 nm. And it shows three PL bands at 460, 630 and 680 nm when excited by 370nm UV light. Figure 6 summarizes the proposed mechanism for the observed luminescence.

Fig. 5. Time-resolved PL spectra of sample F, excitation wavelengths are 300, 335 and 370 nm, respectively.

Fig. 6. Schematic of energy level diagram of Ge-related oxygen defects and transitions involved in the photoluminescence experiment.

Nowadays, there is much interest in cheap, easy generation of white light sources for lighting and display technology, our method opens a new route for the white light illumination [12

12. S. Sivakumar, F. C. J. M. van Veggel, and M. Raudsepp, “Bright white light through up-conversion of a single NIR source from sol-gel-derived thin film made with Ln3+-doped LaF3 nanoparticles,” J. Am. Chem. Soc. 127, 12464–12465 (2005). [CrossRef] [PubMed]

,13

13. M. J. Bowers II, J. R. McBride, and S. J. Rosenthal, “White-light emission from magic-sized cadmium selenide nanocrystals,” J. Am. Chem. Soc. 127, 15378–15379 (2005). [CrossRef]

]. The calculated color coordinates of the white light PL spectra are (0.306, 0.258), (0.308, 0.282), (0.322, 0.305), (0.359, 0.312), and (0.336, 0.339), these fall well within the white region of the 1931 CIE diagram, and is close to the perfect white color coordinates (0.333, 0.333) [19]. It is important to measure the efficiency of the energy conversion from the viewpoint of practical application, further investigation is being carried out.

Figure 7 presents the luminescence spectra of the sample F with the excitation wavelength turning from 300 nm to 395 nm, which indicates that the luminescence could be tunable. The calculated color coordinates of the PL spectra vary from (0.198, 0.204) to (0.335, 0.340) and to (0.516, 0.330). These would fall well within the blue, white and red region respectively as per the 1931 CIE diagram. This phenomenon has shown that the luminescence of the oxygen-deficient glasses is tunable from blue to white to red.

Fig. 7. (a). Photoluminescence spectra of sample F excited by different wavelengths of UV light, which indicates that the luminescence is tunable. (b) CIE chromaticity diagram with coordinates (black circles) shows that the emissions could tunable from blue to white and to red.

4. Conclusion

Acknowledgments

This work was financially supported by National Natural Science Foundation of China (Grant No.50672087 and No. 60778039), National Basic Research Program of China (2006CB806000) and National High Technology Program of China (2006AA03Z304). This work is also supported by Program for Changjiang Scholars and Innovative Research Team in University.

References and links

1.

P. Szuromi and D. Clery, “Control and use of defects in materials,” Science. 281, 939–940 (1998). [CrossRef]

2.

K. O. Hill, Y. Fujii, D. C. Johnson, and B. Kawasaki, “Bragg gratings fabricated in monomode photo-sensitive optical fiber by UV exposure through a phase mask,” Appl. Phys. Lett. 32, 647–649 (1978). [CrossRef]

3.

H. Hosono, Y. Abe, D. L. Kinser, R. A. Weeks, K. Muta, and H. Kawazoe, “Nature and origin of the 5-eV band in SiO2:GeO2 glasses,” Phys. Rev. B 46, 11 445-11 451 (1992). [CrossRef]

4.

E. Yablonovitch, “Inhibited Spontaneous Emission in Solid-State Physics and Electronics,” Phys. Rev. Lett. 58, 2059–2062 (1987). [CrossRef] [PubMed]

5.

Y. Amemiya and J. Miyahara, “Imaging plate illuminates many fields,” Nature (London). 336, 89–90 (1988). [CrossRef]

6.

K. Takahashi, J. Miyahara, and Y. Shibahara, “Photostimulated luminescence (PSL) and color centers in BaFX:Eu2+ (X=Cl, Br, I) phosphors,” J. Electrochem. Soc. 132, 1492–1494 (1985). [CrossRef]

7.

J. Qiu, Y. Shimizugawa, Y. Iwabuchi, and K. Hirao, “Photostimulated luminescence of Ce3+ doped alkali borate glasses,” Appl. Phys. Lett. 71, 43–45 (1997). [CrossRef]

8.

J. Qiu, Y. Shimizugawa, Y. Iwabuchi, and K. Hirao, “Photostimulated luminescence in Eu2+-doped fluoroaluminate glasses,” Appl. Phys. Lett. 71, 759–761 (1997). [CrossRef]

9.

J. Qiu, K. Miura, H. Inouye, Y. Kondo, T. Mitsuyu, and K. Hirao, “Femtosecond laser-induced three-dimensional bright and long-lasting phosphorescence inside calcium aluminosilicate glasses doped with rare earth ions,” Appl. Phys. Lett. 73, 1763–1765 (1998). [CrossRef]

10.

M. C. Wang, J. S. Wang, and M. H. Hon, “Effect of Na2O addition on the optical properties and chemical durability of Li2O-CaO-Al2O3-GeO2 glass,” Jpn. J. Appl. Phys. 33, 2651–2655 (1994). [CrossRef]

11.

L. Huang, X. Liu, W. Xu, B. Chen, and J. Lin, “Infrared and visible luminescence properties of Er3+ and Yb3+ ions codoped Ca3Al2Ge3O12 glass under 978 nm diode laser excitation,” J. Appl. Phys. 90, 5550–5553 (2001). [CrossRef]

12.

S. Sivakumar, F. C. J. M. van Veggel, and M. Raudsepp, “Bright white light through up-conversion of a single NIR source from sol-gel-derived thin film made with Ln3+-doped LaF3 nanoparticles,” J. Am. Chem. Soc. 127, 12464–12465 (2005). [CrossRef] [PubMed]

13.

M. J. Bowers II, J. R. McBride, and S. J. Rosenthal, “White-light emission from magic-sized cadmium selenide nanocrystals,” J. Am. Chem. Soc. 127, 15378–15379 (2005). [CrossRef]

14.

J. M. Stevels, “Ultraviolet transmittivity of glasses,” Proceedings 11th International Congress Pure and Applied Chemistry. 5, 519–521 (1953).

15.

M. Fujimaki, T. Watanabe, T. Katoh, T. Kasahara, N. Miyazaki, Y. Ohki, and H. Nishikawa, “Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings,” Phys. Rev. B 60, 4682–4687 (1999). [CrossRef]

16.

D. P. Poulios, J. P. Spoonhower, and N. P. Bigelow, “Influence of oxygen deficiencies and hydrogen-loading on defect luminescence in irradiated Ge-doped silica glasses,” J. Lumin. 101, 23–33 (2003). [CrossRef]

17.

K. Awazu, K. Muta, and H. Kawazoe, ‘Formation mechanism of hydrogen-associated defect with an 11.9 mT doublet in electron spin resonance and red luminescence in 9SiO2:GeO2 fibers,” J. Appl. Phys. 75, 2237–2240 (1993). [CrossRef]

18.

M. Kohketsu, K. Awazu, H. Kawazoe, and M. Yamane, “Photoluminescence in VAD SiO2:GeO2 glasses sintered under reducing or oxidizing conditions,” Jpn. J. Appl. Phys. 28, 622–631 (1989). [CrossRef]

19.

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/cie.html#c2.

OCIS Codes
(160.2540) Materials : Fluorescent and luminescent materials
(160.4760) Materials : Optical properties

ToC Category:
Materials

History
Original Manuscript: August 6, 2007
Revised Manuscript: October 19, 2007
Manuscript Accepted: October 21, 2007
Published: December 4, 2007

Citation
Geng Lin, Bin Zhu, Shifeng Zhou, Hucheng Yang, and Jianrong Qiu, "Tunable luminescence of CaO-Al2O3-GeO2 glasses," Opt. Express 15, 16980-16985 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-25-16980


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References

  1. P. Szuromi and D. Clery, "Control and use of defects in materials," Science. 281, 939-940 (1998). [CrossRef]
  2. K. O. Hill, Y. Fujii, D. C. Johnson, and B. Kawasaki, "Bragg gratings fabricated in monomode photo-sensitive optical fiber by UV exposure through a phase mask," Appl. Phys. Lett. 32, 647-649 (1978). [CrossRef]
  3. H. Hosono, Y. Abe, D. L. Kinser, R. A. Weeks, K. Muta, and H. Kawazoe, "Nature and origin of the 5-eV band in SiO2:GeO2 glasses," Phys. Rev. B 46, 11 445-11 451 (1992). [CrossRef]
  4. E. Yablonovitch, "Inhibited Spontaneous Emission in Solid-State Physics and Electronics," Phys. Rev. Lett. 58, 2059-2062 (1987). [CrossRef] [PubMed]
  5. Y. Amemiya and J. Miyahara, "Imaging plate illuminates many fields," Nature (London).  336, 89-90 (1988). [CrossRef]
  6. K. Takahashi, J. Miyahara, and Y. Shibahara, "Photostimulated luminescence (PSL) and color centers in BaFX:Eu2+ (X = Cl, Br, I) phosphors," J. Electrochem. Soc. 132, 1492-1494 (1985). [CrossRef]
  7. J. Qiu, Y. Shimizugawa, Y. Iwabuchi, and K. Hirao, "Photostimulated luminescence of Ce3+ doped alkali borate glasses," Appl. Phys. Lett. 71, 43-45 (1997). [CrossRef]
  8. J. Qiu, Y. Shimizugawa, Y. Iwabuchi and K. Hirao, "Photostimulated luminescence in Eu2+-doped fluoroaluminate glasses," Appl. Phys. Lett. 71, 759-761 (1997). [CrossRef]
  9. J. Qiu, K. Miura, H. Inouye, Y. Kondo, T. Mitsuyu, and K. Hirao, "Femtosecond laser-induced three-dimensional bright and long-lasting phosphorescence inside calcium aluminosilicate glasses doped with rare earth ions," Appl. Phys. Lett. 73, 1763-1765 (1998). [CrossRef]
  10. M. C. Wang, J. S. Wang, and M. H. Hon, "Effect of Na2O addition on the optical properties and chemical durability of Li2O-CaO-Al2O3-GeO2 glass," Jpn. J. Appl. Phys. 33, 2651-2655 (1994). [CrossRef]
  11. L. Huang, X. Liu, W. Xu, B. Chen, and J. Lin, "Infrared and visible luminescence properties of Er3+ and Yb3+ ions codoped Ca3Al2Ge3O12 glass under 978 nm diode laser excitation," J. Appl. Phys. 90, 5550-5553 (2001). [CrossRef]
  12. S. Sivakumar, F. C. J. M. van Veggel, and M. Raudsepp, "Bright white light through up-conversion of a single NIR source from sol-gel-derived thin film made with Ln3+-doped LaF3 nanoparticles," J. Am. Chem. Soc. 127, 12464-12465 (2005). [CrossRef] [PubMed]
  13. M. J. BowersII, J. R. McBride, and S. J. Rosenthal, "White-light emission from magic-sized cadmium selenide nanocrystals," J. Am. Chem. Soc. 127, 15378-15379 (2005). [CrossRef]
  14. J. M. Stevels, "Ultraviolet transmittivity of glasses," Proceedings 11th International CongressPure and Applied Chemistry. 5, 519-521 (1953).
  15. M. Fujimaki, T. Watanabe, T. Katoh, T. Kasahara, N. Miyazaki, Y. Ohki, and H. Nishikawa, "Structures and generation mechanisms of paramagnetic centers and absorption bands responsible for Ge-doped SiO2 optical-fiber gratings," Phys. Rev. B 60, 4682-4687 (1999). [CrossRef]
  16. D. P. Poulios, J. P. Spoonhower, and N. P. Bigelow, "Influence of oxygen deficiencies and hydrogen-loading on defect luminescence in irradiated Ge-doped silica glasses," J. Lumin. 101, 23-33 (2003). [CrossRef]
  17. K. Awazu, K. Muta, and H. Kawazoe, ‘Formation mechanism of hydrogen-associated defect with an 11.9 mT doublet in electron spin resonance and red luminescence in 9SiO2:GeO2 fibers," J. Appl. Phys. 75, 2237-2240 (1993). [CrossRef]
  18. M. Kohketsu, K. Awazu, H. Kawazoe and M. Yamane, "Photoluminescence in VAD SiO2:GeO2 glasses sintered under reducing or oxidizing conditions," Jpn. J. Appl. Phys. 28, 622-631 (1989). [CrossRef]
  19. http://hyperphysics.phy-astr.gsu.edu/hbase/vision/cie.html#c2.

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