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Autumn School on Materials Science and Electron Microscopy 2007 "Microscopy - advanced tools for tomorrow's materials" Berlin, October 8th - October 11th, 2007 PREPARATION, CHARACTERISATION AND LUMINESCENCE OF NANOCRYSTALLINE β β β-Ga 2 O 3 :Er AND Y 2 O 3 :Ho Tomislav Biljan 1 , Andreja Gajović 2 and Zlatko Meić 1 1 Department of Chemistry, Faculty of Science, Horvatovac 102a, 10000 Zagreb, Croatia 2 Ruđer Bošković Institute, POB 180, HR-10002 Zagreb, Croatia Luminescence from lanthanide doped materials has attracted much attention in recent years [1], due to their use in the variety of applications in novel light emitting devices; such as phosphors [2], solid state lasers [3], optical amplifiers and optical waveguides especially in the NIR region where optical communication systems operate [1]. There has also been a lot of interest in the use of lanthanide doped materials for up-conversion [4] of infrared to visible light due to potential applications in photonics, optical data storage, lasers and sensors. Doped lanthanide ions can also serve as a sensitive probe of chemistry and structure of host [5]. Particularly interesting is Er 3+ with emission at 1.54 μm that corresponds to the wavelength of minimal optical loss in silica based optical fibers [1]. Nanocrystalline β-Ga 2 O 3 :Er and Y 2 O 3 :Ho [6] have been synthesized by solution combustion method using ethylene glycol as the fuel. Materials are characterized by using X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Luminescence properties of β-Ga 2 O 3 :Er and Y 2 O 3 :Ho are studied using two Raman spectrometers with excitation in NIR and visible. The variety in the shape and size of particles, in both β-Ga 2 O 3 :Er and Y 2 O 3 :Ho, was observed by TEM (Fig. 1). The histogram of the particle size distribution (Fig. 2a) for β-Ga 2 O 3 :Er and (Fig. 2b) for Y 2 O 3 :Ho confirms the predominance of the small particle sizes with a log- normal distribution. The mean particle size calculated from the distribution was 16.9(5) nm for β-Ga 2 O 3 :Er and 27.6(9) nm for Y 2 O 3 :Ho, which is in line with values of the average crystallite size estimated from XRD measurements (21(3) nm for β-Ga 2 O 3 :Er and 25(2) nm for Y 2 O 3 :Ho). The appearance of the rings in SAED patterns (inserts in Fig. 1) indicated nanosized crystallites, as observed by TEM, and determined from broadening of the XRD lines. Luminescence properties have been studied by using Raman spectrometers with excitation in NIR and visible. All bands present in spectra of β-Ga 2 O 3 :Er are assigned to 4f 11 4f 11 transitions of Er 3+ and bands present in spectra of Y 2 O 3 :Ho to 4f 10 4f 10 transitions of Ho 3+ . Main characteristic of luminescence spectrum of β-Ga 2 O 3 :Er is a strong Er 3+ NIR emission at 1.54 μm due to the 4 I 13/2 4 I 15/2 transition under the 1064 nm excitation. The intensity of this technologically important transition can be significantly (around 60 times) increased by the Yb 3+ codoping. Main characteristics of luminescence spectra of nanocrystalline Y 2 O 3 :Ho are strong emissions between 1120 and 1225 nm and 710 and 765 nm due to the 5 I 6 5 I 8 and ( 5 S 2 + 5 F 4 ) 5 I 7 transitions of Ho 3+ , respectively [6].
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Transcript of PREPARATION, CHARACTERISATION AND ...crysta.physik.hu-berlin.de/as2007/pdf/extended_abstracts/.........

  • Autumn School on Materials Science and Electron Microscopy 2007

    "Microscopy - advanced tools for tomorrow's materials"

    Berlin, October 8th - October 11th, 2007

    PREPARATION, CHARACTERISATION AND LUMINESCENCE OF

    NANOCRYSTALLINE

    -Ga2O3:Er AND Y2O3:Ho

    Tomislav Biljan1, Andreja Gajovi

    2 and Zlatko Mei

    1

    1Department of Chemistry, Faculty of Science, Horvatovac 102a, 10000 Zagreb, Croatia

    2 Ruer Bokovi Institute, POB 180, HR-10002 Zagreb, Croatia

    Luminescence from lanthanide doped materials has attracted much attention in recent years

    [1], due to their use in the variety of applications in novel light emitting devices; such as

    phosphors [2], solid state lasers [3], optical amplifiers and optical waveguides especially in

    the NIR region where optical communication systems operate [1]. There has also been a lot of

    interest in the use of lanthanide doped materials for up-conversion [4] of infrared to visible

    light due to potential applications in photonics, optical data storage, lasers and sensors. Doped

    lanthanide ions can also serve as a sensitive probe of chemistry and structure of host [5].

    Particularly interesting is Er3+

    with emission at 1.54 m that corresponds to the wavelength of

    minimal optical loss in silica based optical fibers [1].

    Nanocrystalline -Ga2O3:Er and Y2O3:Ho [6] have been synthesized by solution combustion method using ethylene glycol as the fuel. Materials are characterized by using X-ray powder

    diffraction (XRD) and transmission electron microscopy (TEM). Luminescence properties of

    -Ga2O3:Er and Y2O3:Ho are studied using two Raman spectrometers with excitation in NIR and visible.

    The variety in the shape and size of particles, in both -Ga2O3:Er and Y2O3:Ho, was observed by TEM (Fig. 1). The histogram of the particle size distribution (Fig. 2a) for -Ga2O3:Er and (Fig. 2b) for Y2O3:Ho confirms the predominance of the small particle sizes with a log-

    normal distribution. The mean particle size calculated from the distribution was 16.9(5) nm

    for -Ga2O3:Er and 27.6(9) nm for Y2O3:Ho, which is in line with values of the average crystallite size estimated from XRD measurements (21(3) nm for -Ga2O3:Er and 25(2) nm for Y2O3:Ho). The appearance of the rings in SAED patterns (inserts in Fig. 1) indicated

    nanosized crystallites, as observed by TEM, and determined from broadening of the XRD

    lines.

    Luminescence properties have been studied by using Raman spectrometers with excitation in

    NIR and visible. All bands present in spectra of -Ga2O3:Er are assigned to 4f11

    4f11

    transitions of Er3+

    and bands present in spectra of Y2O3:Ho to 4f10

    4f10

    transitions of Ho3+

    .

    Main characteristic of luminescence spectrum of -Ga2O3:Er is a strong Er3+

    NIR emission at

    1.54 m due to the 4I13/2

    4I15/2 transition under the 1064 nm excitation. The intensity of this

    technologically important transition can be significantly (around 60 times) increased by the

    Yb3+

    codoping. Main characteristics of luminescence spectra of nanocrystalline Y2O3:Ho are

    strong emissions between 1120 and 1225 nm and 710 and 765 nm due to the 5I6

    5I8 and (

    5S2

    + 5F4)

    5I7 transitions of Ho

    3+, respectively [6].

  • a) b)

    Figure 1. TEM and SAED of: a) -Ga2O3:Er and b) Y2O3:Ho

    a) b)

    Particle sizes / nm = 323*1*lognorm(x, 3.1788, 0.5181)

    6 13 20 27 34 41 48 55 62 69 76 83 90 97

    Particle sizes / nm

    0

    2

    4

    6

    8

    10

    12

    14

    16

    18

    20

    No

    of

    part

    icle

    s

    Figure 2. Distribution of the particle sizes observed by TEM a) -Ga2O3:Er and b) Y2O3:Ho

    [1] A. J. Kenyon, Progr. Quant. Electr. 26 (2002) 225.

    [2] S. Ekambaram, K. C. Patil, M. Maaza, J. Alloys. Compd. 393 (2005) 81.

    [3] W. Koechner, Solid-State Laser Engineering, Springer Verlag, New York, 1999.

    [4] F. Auzel, Chem. Rev. 104 (2004) 139.

    [5] A. Polman, Physica B. 300 (2001) 78.

    [6] T. Biljan, A. Gajovi, Z. Mei, E. Metrovi, J. Alloys Compd., 431 (2007) 217-220.