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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 3 — Jan. 31, 2011
  • pp: 1824–1829
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Effects of site substitutions and concentration on upconversion luminescence of Er3+-doped perovskite titanate

Yang Zhang, Jianhua Hao, Chee Leung Mak, and Xianhua Wei  »View Author Affiliations


Optics Express, Vol. 19, Issue 3, pp. 1824-1829 (2011)
http://dx.doi.org/10.1364/OE.19.001824


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Abstract

Upconversion photoluminescence (PL) of Er3+-doped BaTiO3 (BTO) with perovskite ABO3 structure is studied in terms of Er3+ substitutions for Ba (A-) and Ti (B-site) with different Er3+ doping concentrations. PL quenching with an increase Er3+ doping concentration is investigated based on the structural change and energy transfer of cross-relaxation process in BTO: Er, i.e. 2H11/2 + 4I15/24I9/2 + 4I13/2. Temperature dependence of the PL in BTO: Er is revealed, which is associated with phase transitions of BTO host. The results imply that the emission from substituted Er3+ ions may be used as a structural probe for the ferroelectric titanates.

© 2011 OSA

1. Introduction

2. Experiment

Er3+-doped BTO powders with different site substitutions and concentrations were prepared by solid-state reaction method. Reagent grade BaCO3, TiO2, and Er2O3 powders were used as raw materials. The charge compensation could be compensated by barium and oxygen vacancy for the A- and B-site substitutions, respectively. Here the samples for A- and B-site substitutions are refered to Ba1-3x/2ErxTiO3 (BTO: A) and BaTi1-xErxO3-x/2 (BTO: B), respectively. Based on the above formulas, the starting powders with designed stoichiometric quantities were ball milled for 24 h, then dried and calcinated at 1100 °C for 8 h in air to generate the Er3+-doped BTO powders.

The crystal structure of the samples was examined by a Bruker D8 Advance X-ray diffractometer (XRD). Raman spectra were measured using a Horiba Jobin Yvon HR800 Raman spectrometer with a 488 nm laser excitation source. The PL spectra were recorded using an Edinburgh FLSP920 spectrophotometer under the excitation of a 980 nm laser diode. The fluorescence lifetimes for Er3+ were recorded at 552 nm with a μF900H micro-second flashlamp (λex = 488 nm) as the excitation sources. The temperature-dependent PL spectra were carried out in the temperature range of 15-300 K.

3. Results and discussion

Figure 1
Fig. 1 XRD patterns of the pure BTO and Er3+-doped BTO with different site substitutions and concentrations: (a) pure, (b) x = 3 mol% with A-site substitution, (c) x = 3 mol% with B-site substitution and (d) x = 5 mol% with B-site substitution. The inset shows the enlarged (111) peak.
shows the XRD patterns of Er3+-doped BTO with different site substitutions and concentrations. The characteristic diffraction peaks of tetragonal BTO phase without secondary impurity phases were observed. The result implied that Er3+ ions were doped efficiently into BTO host. A comparison of these XRD patterns with various Er3+ doping shows the broaden diffraction peaks for samples with higher Er3+ doping concentrations as shown in Fig. 1. It suggests that the doping with higher Er3+ concentrations may lead to the worse crystalline of doped BTO. In addition, compared with pure BTO, there are minor shifts of the diffraction peak (111) for the Er3+ doped samples as seen in the inset of Fig. 1. It means that the lattice constant of Er3+-doped BTO shrinks or expands in the case of Er3+ occupying A- or B-site, respectively [12

12. V. V. Mitic, Z. S. Nikolic, V. B. Pavlovic, V. Paunovic, M. Miljkovic, B. Jordovic, and L. Zivkovic, “Influence of rare-earth dopants on barium titanate ceramics microstructure and corresponding electrical properties,” J. Am. Ceram. Soc. 93(1), 132–137 (2010). [CrossRef]

,19

19. C. E. Jiang, L. Fang, M. R. Shen, F. G. Zheng, and X. L. Wu, “Effects of Eu substituting positions and concentrations on luminescent, dielectric, and magnetic properties of SrTiO3 ceramics,” Appl. Phys. Lett. 94(7), 071110 (2009). [CrossRef]

].

Figure 2
Fig. 2 Raman spectra of the pure BTO and Er3+-doped BTO with different site substitutions and concentrations.
gives the Raman spectra of Er3+-doped BTO and pure BTO at room temperature. BTO exhibits tetragonal structure belonging to the space group C4v symmetry. All of the features observed in the tetragonal phase have been reported in the literature [16

16. P. S. Dobal and R. S. Katiyar, “Studies on ferroelectric perovskites and Bi-layered compounds using micro-Raman spectroscopy,” J. Raman Spectrosc. 33(6), 405–423 (2002). [CrossRef]

]. The peak observed at 305 cm−1 corresponds to the E(TO2) phonon mode of tetragonal BTO. The A1(TO1), A1(TO2), A1(TO3) and A1(LO3) modes were observed at about 180, 270, 516 and 720 cm−1, respectively. Raman spectra obtained from Er3+-doped BTO did not show any remarkable wavelength shift. It can also be seen that all Raman modes become weaker and broader with an increase in Er3+ concentration. It indicates the higher Er3+ concentration results in the worse crystallinity, which is consistent with the XRD results.

Figure 3
Fig. 3 The PL spectra of BTO: A with x = 3 mol% (red) and BTO: B with x = 0.5 mol% (magenta), 1 mol% (cyan), 3 mol% (blue) and 5 mol% (black). The inset shows the green-to-red ratio (I523nm/I656nm) vs dopant concentration.
shows the PL spectra of BTO doped with different Er3+ ion concentrations and site substitutions measured at room temperature. The typical UC emission consists of two strong green bands located at 523 and 552 nm corresponding to 2H11/2/4S3/24I15/2 transitions, and a weak red emission band at 656 nm ascribed to 4F9/24I15/2 transition of the Er3+ ion, respectively. Obvious Stark-splitting can be observed in all samples. Note that with an increase in Er3+ doping concentration (0.5-5 mol% for BTO: B), the emission intensity reaches a maximum value at 1 mol%, and then decreases with an increase in doping concentration. There are two reasons responsible for this observation. Structural analysis based on XRD and Raman spectra has revealed that worse crystalline occurs in BTO: Er with increasing Er3+ content. Worse crystalline phase corresponds to higher defect density of the materials. Both subband gap defect levels and impurity atoms in the grain boundaries could participate in the relaxation process and change the probability of radiative recombination [17

17. J. H. Hao, S. A. Studenikin, and M. Cocivera, “Transient photoconductivity properties of tungsten oxide thin films prepared by spray pyrolysis,” J. Appl. Phys. 90(10), 5064–5069 (2001). [CrossRef]

,18

18. Z. L. Wang, H. L. W. Chan, H. L. Li, and J. H. Hao, “Highly efficient low-voltage cathodoluminescence of LaF3:Ln3+ (Ln=Eu3+, Ce3+, Tb3+) spherical particles,” Appl. Phys. Lett. 93(14), 141106 (2008). [CrossRef]

]. On the other hand, an increased dopant concentration could also enhance CR process with remarkable decrease UC emission as shown in Fig. 4
Fig. 4 Schematic diagram for the UC mechanism of Er3+ ions under 980 nm excitation.
. Under the excitation of 980 nm, through excited state absorption (ESA) or energy transfer (ET) process, Er3+ ion can populates the 4F7/2 level. Subsequently, the Er3+ ion then relaxes nonradiatively to the 2H11/2 and 4S3/2 levels by multiphonon relaxation, from which the green 2H11/2/4S3/24I15/2 emissions occur. As shown in Fig. 3, red UC emissions from the 4F9/2 state are weak, since the 4F9/2 state has a relatively large energy separation below the 4S3/2 state, compared with the phonon energy of the BTO lattice. Moreover, we calculated the intensity of green-to-red ratio (I523nm/I656nm) for the BTO: B sample as shown in the inset of Fig. 3. It can be seen that the ratio (I523nm/I656nm) is 23.4, 24.2, 5.7, and 1.8 for 0.5, 1, 3, and 5 mol% B-site Er3+-doped BTO, respectively. The result can be understood based on the CR process shown in Fig. 4. Higher Er3+ concentration contributing to a shorter distance between ions results in an enhanced ET probability of the CR process, i.e. 2H11/2 + 4I15/24I9/2 + 4I13/2. Hence, the Er3+ ions at 4I13/2 state through ESA populate the 4F9/2 state. This enhanced population of the 4F9/2 state primarily enhances the intensity of the red emission.

The PL spectra of BTO with 3 mol% Er3+ ion doped for A- and B-site substitutions are also presented in Fig. 3. The PL intensity differs for different site substitutions, but there is no obvious shift of the emission peaks. These results indicate that the crystal field surrounding the erbium ions can change the relative radiative probability of the transitions from the excited state to the eight Stark components of the 4I15/2 ground state. The PL intensity of A-site doped sample is much stronger than that of B-site doped BTO. Compared with that of A-site doped sample, the decrease in PL intensity for B-site substitution Er3+-doped BTO may be affected by oxygen vacancies when Er3+ as an acceptor type impurity replaces Ti site, leading to an oxygen-deficient nonstoichiometry [13

13. J. H. Hwang and Y. H. Han, “Dielectric properties of erbium doped barium titanate,” Jpn. J. Appl. Phys. 40(Part 1, No. 2A), 676–679 (2001). [CrossRef]

,19

19. C. E. Jiang, L. Fang, M. R. Shen, F. G. Zheng, and X. L. Wu, “Effects of Eu substituting positions and concentrations on luminescent, dielectric, and magnetic properties of SrTiO3 ceramics,” Appl. Phys. Lett. 94(7), 071110 (2009). [CrossRef]

]. Compared the fluorescence lifetimes for two samples at 552 nm corresponding to 4S3/24I15/2 transition, the double exponential fitting results for A- and B-site doped samples are 132 and 52 ms, respectively. The decrease of lifetime of B-site substituted sample could be ascribed to the introduction of oxygen vacancies. We speculate that these oxygen vacancies would induce mew energy levels, which promote nonradiative energy transfer.

4. Conclusions

In conclusion, PL quenching of Er3+-doped BTO is due to the worse crystalline and cross-relaxation with an increase in Er3+ doping concentration. Phase transition results in the increase of PL spectra of A-site doped BTO across the phase transition temperature. For the case of B-site substitution, 4S3/24I15/2 emissions are strongly enhanced due to thermal quenching and lower symmetry induced by phase transition.

Acknowledgments

The work was supported by grants from the Research Grants Council of Hong Kong (GRF No. PolyU500910) and Hong Kong Polytechnic University (No. A-PH89).

References and links

1.

J. E. Daniels, W. Jo, J. Rödel, and J. L. Jones, “Electric-field-induced phase transformation at a lead-free morphotropic phase boundary: case study in a 93%(Bi0.5Na0.5)TiO3-7% BaTiO3 piezoelectric ceramic,” Appl. Phys. Lett. 95(3), 032904 (2009). [CrossRef]

2.

S. Tinte and M. G. Stachiotti, “Surface effects and ferroelectric phase transitions in BaTiO3 ultrathin films,” Phys. Rev. B 64(23), 235403 (2001). [CrossRef]

3.

J. H. Hao, J. Gao, Z. Wang, and D. P. Yu, “Interface structure and phase of epitaxial SrTiO3 (100) thin films grown directly on silicon,” Appl. Phys. Lett. 87(13), 131908 (2005). [CrossRef]

4.

R. A. Ganeev, M. Suzuki, M. Baba, M. Ichihara, and H. Kuroda, “Low- and high-order nonlinear optical properties of BaTiO3 and SrTiO3 nanoparticles,” J. Opt. Soc. Am. B 25(3), 325–333 (2008). [CrossRef]

5.

Y. X. Liu, W. A. Pisarski, S. J. Zeng, C. F. Xu, and Q. B. Yang, “Tri-color upconversion luminescence of Rare earth doped BaTiO3 nanocrystals and lowered color separation,” Opt. Express 17(11), 9089–9098 (2009). [CrossRef] [PubMed]

6.

G. Schlaghechen, J. Gottmann, E. W. Kreutz, and R. Poprawe, “Pulsed laser deposition of Er: BaTiO3 for planar waveguides,” Appl. Phys., A Mater. Sci. Process. 79, 1255–1257 (2004).

7.

A. Polman, “Erbium as a probe of everything?” Physica B 300(1-4), 78–90 (2001). [CrossRef]

8.

N. M. Samsuri, A. K. Zamzuri, M. H. Al-Mansoori, A. Ahmad, and M. A. Mahdi, “Brillouin-Erbium fiber laser with enhanced feedback coupling using common Erbium gain section,” Opt. Express 16(21), 16475–16480 (2008). [CrossRef] [PubMed]

9.

K. Takada, E. Chang, and D. M. Smyth, “Rare-earth addition to BaTiO3,” Adv. Ceram. 19, 147–152 (1987).

10.

T. D. Dunbar, W. L. Warren, B. A. Tuttle, C. A. Randall, and Y. Tsur, “Electron paramagnetic resonance investigations of lanthanide-doped barium titanate: dopant site occupancy,” J. Phys. Chem. B 108(3), 908–917 (2004). [CrossRef]

11.

M. T. Buscaglia, M. Viviani, V. Buscaglia, C. Bottino, and P. Nanni, “Incorporation of Er3+ into BaTiO3,” J. Am. Ceram. Soc. 85(6), 1569–1575 (2002). [CrossRef]

12.

V. V. Mitic, Z. S. Nikolic, V. B. Pavlovic, V. Paunovic, M. Miljkovic, B. Jordovic, and L. Zivkovic, “Influence of rare-earth dopants on barium titanate ceramics microstructure and corresponding electrical properties,” J. Am. Ceram. Soc. 93(1), 132–137 (2010). [CrossRef]

13.

J. H. Hwang and Y. H. Han, “Dielectric properties of erbium doped barium titanate,” Jpn. J. Appl. Phys. 40(Part 1, No. 2A), 676–679 (2001). [CrossRef]

14.

P. Z. Zhang, M. R. Shen, L. Fang, F. G. Zheng, X. L. Wu, J. C. Shen, and H. T. Chen, “Pr3+ photoluminescence in ferroelectric (Ba0.77Ca0.23)TiO3 ceramics: sensitive to polarization and phase transitions,” Appl. Phys. Lett. 92(22), 222908 (2008). [CrossRef]

15.

C. H. Wen, S. Y. Chu, Y. D. Juang, and C. K. Wen, “New phase transition of erbium-doped KNbO3 polycrystalline,” J. Cryst. Growth 280(1-2), 179–184 (2005). [CrossRef]

16.

P. S. Dobal and R. S. Katiyar, “Studies on ferroelectric perovskites and Bi-layered compounds using micro-Raman spectroscopy,” J. Raman Spectrosc. 33(6), 405–423 (2002). [CrossRef]

17.

J. H. Hao, S. A. Studenikin, and M. Cocivera, “Transient photoconductivity properties of tungsten oxide thin films prepared by spray pyrolysis,” J. Appl. Phys. 90(10), 5064–5069 (2001). [CrossRef]

18.

Z. L. Wang, H. L. W. Chan, H. L. Li, and J. H. Hao, “Highly efficient low-voltage cathodoluminescence of LaF3:Ln3+ (Ln=Eu3+, Ce3+, Tb3+) spherical particles,” Appl. Phys. Lett. 93(14), 141106 (2008). [CrossRef]

19.

C. E. Jiang, L. Fang, M. R. Shen, F. G. Zheng, and X. L. Wu, “Effects of Eu substituting positions and concentrations on luminescent, dielectric, and magnetic properties of SrTiO3 ceramics,” Appl. Phys. Lett. 94(7), 071110 (2009). [CrossRef]

20.

E. Na, S. C. Choi, and U. Paik, “Temperature dependence of dielectric properties of rare earth element doped BaTiO3,” J. Ceram. Process. Res. 4(4), 181–184 (2003).

21.

M. Ishii, S. Komuro, T. Morikawa, and Y. Aoyagi, “Local structure analysis of optically active center in Er-doped ZnO thin film,” J. Appl. Phys. 89(7), 3679–3684 (2001). [CrossRef]

22.

Z. Zhou, T. Komori, T. Ayukawa, H. Yukawa, M. Morinaga, A. Koizumi, and Y. Takeda, “Li- and Er-codoped ZnO with enhanced 1.54 μm photoemission,” Appl. Phys. Lett. 87(9), 091109 (2005). [CrossRef]

OCIS Codes
(160.2260) Materials : Ferroelectrics
(160.5690) Materials : Rare-earth-doped materials
(190.7220) Nonlinear optics : Upconversion

ToC Category:
Materials

History
Original Manuscript: December 14, 2010
Revised Manuscript: January 11, 2011
Manuscript Accepted: January 11, 2011
Published: January 14, 2011

Citation
Yang Zhang, Jianhua Hao, Chee Leung Mak, and Xianhua Wei, "Effects of site substitutions and concentration on upconversion luminescence of Er3+-doped perovskite titanate," Opt. Express 19, 1824-1829 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-3-1824


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References

  1. J. E. Daniels, W. Jo, J. Rödel, and J. L. Jones, “Electric-field-induced phase transformation at a lead-free morphotropic phase boundary: case study in a 93%(Bi0.5Na0.5)TiO3-7% BaTiO3 piezoelectric ceramic,” Appl. Phys. Lett. 95(3), 032904 (2009). [CrossRef]
  2. S. Tinte and M. G. Stachiotti, “Surface effects and ferroelectric phase transitions in BaTiO3 ultrathin films,” Phys. Rev. B 64(23), 235403 (2001). [CrossRef]
  3. J. H. Hao, J. Gao, Z. Wang, and D. P. Yu, “Interface structure and phase of epitaxial SrTiO3 (100) thin films grown directly on silicon,” Appl. Phys. Lett. 87(13), 131908 (2005). [CrossRef]
  4. R. A. Ganeev, M. Suzuki, M. Baba, M. Ichihara, and H. Kuroda, “Low- and high-order nonlinear optical properties of BaTiO3 and SrTiO3 nanoparticles,” J. Opt. Soc. Am. B 25(3), 325–333 (2008). [CrossRef]
  5. Y. X. Liu, W. A. Pisarski, S. J. Zeng, C. F. Xu, and Q. B. Yang, “Tri-color upconversion luminescence of Rare earth doped BaTiO3 nanocrystals and lowered color separation,” Opt. Express 17(11), 9089–9098 (2009). [CrossRef] [PubMed]
  6. G. Schlaghechen, J. Gottmann, E. W. Kreutz, and R. Poprawe, “Pulsed laser deposition of Er: BaTiO3 for planar waveguides,” Appl. Phys., A Mater. Sci. Process. 79, 1255–1257 (2004).
  7. A. Polman, “Erbium as a probe of everything?” Physica B 300(1-4), 78–90 (2001). [CrossRef]
  8. N. M. Samsuri, A. K. Zamzuri, M. H. Al-Mansoori, A. Ahmad, and M. A. Mahdi, “Brillouin-Erbium fiber laser with enhanced feedback coupling using common Erbium gain section,” Opt. Express 16(21), 16475–16480 (2008). [CrossRef] [PubMed]
  9. K. Takada, E. Chang, and D. M. Smyth, “Rare-earth addition to BaTiO3,” Adv. Ceram. 19, 147–152 (1987).
  10. T. D. Dunbar, W. L. Warren, B. A. Tuttle, C. A. Randall, and Y. Tsur, “Electron paramagnetic resonance investigations of lanthanide-doped barium titanate: dopant site occupancy,” J. Phys. Chem. B 108(3), 908–917 (2004). [CrossRef]
  11. M. T. Buscaglia, M. Viviani, V. Buscaglia, C. Bottino, and P. Nanni, “Incorporation of Er3+ into BaTiO3,” J. Am. Ceram. Soc. 85(6), 1569–1575 (2002). [CrossRef]
  12. V. V. Mitic, Z. S. Nikolic, V. B. Pavlovic, V. Paunovic, M. Miljkovic, B. Jordovic, and L. Zivkovic, “Influence of rare-earth dopants on barium titanate ceramics microstructure and corresponding electrical properties,” J. Am. Ceram. Soc. 93(1), 132–137 (2010). [CrossRef]
  13. J. H. Hwang and Y. H. Han, “Dielectric properties of erbium doped barium titanate,” Jpn. J. Appl. Phys. 40(Part 1, No. 2A), 676–679 (2001). [CrossRef]
  14. P. Z. Zhang, M. R. Shen, L. Fang, F. G. Zheng, X. L. Wu, J. C. Shen, and H. T. Chen, “Pr3+ photoluminescence in ferroelectric (Ba0.77Ca0.23)TiO3 ceramics: sensitive to polarization and phase transitions,” Appl. Phys. Lett. 92(22), 222908 (2008). [CrossRef]
  15. C. H. Wen, S. Y. Chu, Y. D. Juang, and C. K. Wen, “New phase transition of erbium-doped KNbO3 polycrystalline,” J. Cryst. Growth 280(1-2), 179–184 (2005). [CrossRef]
  16. P. S. Dobal and R. S. Katiyar, “Studies on ferroelectric perovskites and Bi-layered compounds using micro-Raman spectroscopy,” J. Raman Spectrosc. 33(6), 405–423 (2002). [CrossRef]
  17. J. H. Hao, S. A. Studenikin, and M. Cocivera, “Transient photoconductivity properties of tungsten oxide thin films prepared by spray pyrolysis,” J. Appl. Phys. 90(10), 5064–5069 (2001). [CrossRef]
  18. Z. L. Wang, H. L. W. Chan, H. L. Li, and J. H. Hao, “Highly efficient low-voltage cathodoluminescence of LaF3:Ln3+ (Ln=Eu3+, Ce3+, Tb3+) spherical particles,” Appl. Phys. Lett. 93(14), 141106 (2008). [CrossRef]
  19. C. E. Jiang, L. Fang, M. R. Shen, F. G. Zheng, and X. L. Wu, “Effects of Eu substituting positions and concentrations on luminescent, dielectric, and magnetic properties of SrTiO3 ceramics,” Appl. Phys. Lett. 94(7), 071110 (2009). [CrossRef]
  20. E. Na, S. C. Choi, and U. Paik, “Temperature dependence of dielectric properties of rare earth element doped BaTiO3,” J. Ceram. Process. Res. 4(4), 181–184 (2003).
  21. M. Ishii, S. Komuro, T. Morikawa, and Y. Aoyagi, “Local structure analysis of optically active center in Er-doped ZnO thin film,” J. Appl. Phys. 89(7), 3679–3684 (2001). [CrossRef]
  22. Z. Zhou, T. Komori, T. Ayukawa, H. Yukawa, M. Morinaga, A. Koizumi, and Y. Takeda, “Li- and Er-codoped ZnO with enhanced 1.54 μm photoemission,” Appl. Phys. Lett. 87(9), 091109 (2005). [CrossRef]

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