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The ternary phosphate glass series (50-x)CaO–xCaF2–50P2O5 (x = 0–20 mol%) were synthesized using melt quench technique. Structural, optical and mechanical properties were investigated with increase in CaF2 content. Using X-ray diffraction (XRD), synthesized glasses were confirmed to be amorphous in nature. Replacement of oxygen ions by fluorine ions increased the values of density. Decrease in refractive index due to the low polarizability of fluorine ions in the glass matrix was observed. In Fourier transform infrared (FTIR) spectra, the slight variation in νas (PO2) band position and intensity could be attributed to replacement of fluorine ions for oxygen ions in phosphate glass structure. These data were well supported by Raman spectra. Optical band gap energy increased from 3.44 eV to 3.64 eV with increase in CaF2 content, and Urbach energy decreased suggesting that the fluorine ions reduced the tail energy states in the band gap compared to the oxygen ions. Mechanical parameters such as Vickers hardness, fracture toughness and brittleness were evaluated from the Vickers micro indentation measurements. Increase in Vickers hardness, decrease in fracture toughness and increase in brittleness were observed with increase in CaF2 content.


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Structural, optical and mechanical properties of ternary CaO–CaF2–P2O5 glasses

Show Author's information G. VENKATESWARA RAO( )H. D. SHASHIKALA
Department of Physics, National Institute of Technology Karnataka, Surathkal, Post Srinivasanagar, Mangalore-575025, Karnataka, India

Abstract

The ternary phosphate glass series (50-x)CaO–xCaF2–50P2O5 (x = 0–20 mol%) were synthesized using melt quench technique. Structural, optical and mechanical properties were investigated with increase in CaF2 content. Using X-ray diffraction (XRD), synthesized glasses were confirmed to be amorphous in nature. Replacement of oxygen ions by fluorine ions increased the values of density. Decrease in refractive index due to the low polarizability of fluorine ions in the glass matrix was observed. In Fourier transform infrared (FTIR) spectra, the slight variation in νas (PO2) band position and intensity could be attributed to replacement of fluorine ions for oxygen ions in phosphate glass structure. These data were well supported by Raman spectra. Optical band gap energy increased from 3.44 eV to 3.64 eV with increase in CaF2 content, and Urbach energy decreased suggesting that the fluorine ions reduced the tail energy states in the band gap compared to the oxygen ions. Mechanical parameters such as Vickers hardness, fracture toughness and brittleness were evaluated from the Vickers micro indentation measurements. Increase in Vickers hardness, decrease in fracture toughness and increase in brittleness were observed with increase in CaF2 content.

Keywords:

phosphate glass, Fourier transform infrared (FTIR) spectra, Raman spectra, mechanical properties
Received: 07 January 2014 Revised: 20 February 2014 Accepted: 28 February 2014 Published: 01 June 2014 Issue date: June 2014
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Publication history

Received: 07 January 2014
Revised: 20 February 2014
Accepted: 28 February 2014
Published: 01 June 2014
Issue date: June 2014

Copyright

© The author(s) 2014

Acknowledgements

One of the authors GVR thanks National Institute of Technology Karnataka, Surathkal, for providing the institute fellowship. The authors thank Nano Functional Materials Technology Centre (NFMTC), Indian Institute of Technology Madras for carrying out Raman spectroscopy measurements.

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