Structural and optical properties of low cost zinc silicate-based glass ceramics doped with europium
To date, the demand for better light emitting diodes (LEDs) has led to growing interest in producing Zn2SiO4 based glass ceramic phosphors using waste materials. In this research, low cost Zn2SiO4:xEu3+ phosphors were prepared based on a solid state method using recyclable glass wastes as silica...
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Format: | Thesis |
Language: | English |
Published: |
2016
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/69942/1/ITMA%202016%206%20IR.pdf http://psasir.upm.edu.my/id/eprint/69942/ |
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Summary: | To date, the demand for better light emitting diodes (LEDs) has led to growing interest
in producing Zn2SiO4 based glass ceramic phosphors using waste materials. In this
research, low cost Zn2SiO4:xEu3+ phosphors were prepared based on a solid state
method using recyclable glass wastes as silica source. The influence of Eu3+ ions (x =
0, 1, 2, 3, 4 and 5 wt.%) and the effect of sintering temperatures, ranging from 600 to
1000 °C on the structural, morphological and optical properties of the phosphors were
also investigated using X-ray diffraction (XRD), Field emission scanning electron
microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, Raman
spectroscopy, Ultraviolet-visible near infrared (UV-Vis-NIR) spectroscopy and
Photoluminescence (PL) spectroscopy. These glass ceramics showed the increasing
densities with increasing Eu3+ and sintering temperature. Structural investigation using
XRD had revealed that the higher intensities of the diffraction peaks were due to
sintering temperatures. Furthermore, their diffraction peaks had slightly shifted to
lower diffraction angles when the dopant’s concentration was increased. The
morphologies from FESEM analysis showed the formation of densely packed grains
and smooth surfaces with the increment of sintering temperatures and addition of
dopants. FTIR spectra showed that the progression of sintering temperature has
narrowed the broad bands of SiO4 and ZnO4 at 1000 °C. All the broad bands were
reduced to smaller bands after the addition of dopant. Additionally, the effects of
sintering temperatures and dopants on the samples were apparent on the Raman
spectra, which showed the narrow width of Raman lines and the shifted energy region
in the spectrum. Most importantly, the largest optical band gaps of the samples were
found at the highest sintering temperature. Meanwhile, Eu3+ doped samples have
shown the largest optical band gap at 1000 °C upon the examination of the Moss-
Burstein effect. Results for the photoluminescence showed red luminescence
emissions at 600 nm due to Eu3+ transitions under 400 nm excitation. It was observed
that sintering temperatures of 900 and 1000 °C have decreased the intensity of
emission, while the highest doping concentration of 5 wt.% of Eu3+ has shown the
highest emission intensity of the phosphors. Apart from that, waste silica sources have
proven to have excellent crystallinity, surface morphology, optical band gap and emission intensity for obtaining red emitting phosphors, which could also be useful for
white LEDs. |
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