Fictive temperature of GeO2 glass: Its determination by IR method and its effects on density and refractive index

doi:10.1016/j.jnoncrysol.2007.06.057

Journal of Non-Crystalline Solids

Volume 353, Issues 52–54, 15 December 2007, Pages 4762-4766

https://doi.org/10.1016/j.jnoncrysol.2007.06.057 Get rights and content

Abstract

A simple IR method of determining the fictive temperature of GeO₂ glass, both surface and bulk, was developed using the same technique developed earlier for silica glass. Specifically, IR absorption and reflection peak wavenumbers of GeO₂ structural bands were found to be correlated with the fictive temperature of the glass. Using this method structural relaxation kinetics can be investigated. Density and refractive index of GeO₂ glass were also measured as a function of fictive temperature.

Introduction

A glass exhibits different structures and properties depending on the cooling rate from its melt. The cooling rate affects the temperature at which the supercooled liquid freezes to form the glassy state, the faster cooling rate shifting the temperature higher. The temperature at which the liquid structure freezes to turn into glass is known as the fictive temperature [1]. If a glass is held at a given temperature in the glass transition range, then the fictive temperature of the glass will approach the heat-treatment temperature over time. Many properties of glasses including density, refractive index, hardness, bulk modulus, and ionic diffusivity depend on fictive temperature.

It has been shown that the peak wavenumber of infrared structural bands in various glasses including silica glasses are correlated with the fictive temperature and can be used as a simple measure of fictive temperature [2]. It is expected that the same technique is applicable to germanium dioxide glasses since these glasses exhibit similar structural bands to those of silica glass [3], [4], [5], [6]. This possibility was explored.

Glasses can be classified as either normal or anomalous depending on their fictive temperature–property relationship. In general, normal glasses exhibit increasing specific volume, decreasing density, decreasing refractive index, and decreasing hardness with increasing fictive temperature. Anomalous glasses show an opposite trend in these properties.

Tetrahedrally coordinated glasses including germanium dioxide and silicon dioxide have been shown to exhibit anomalous behavior in their mechanical properties as shown by Kurkjian et al. [7]. Anomalies in the temperature and pressure coefficients of shear and bulk moduli are present in these glasses. SiO₂ glasses are known to exhibit anomalous behavior in the fictive temperature dependence of density and refractive index. Fictive temperature dependence of density and refractive index of GeO₂ glass was examined to see whether GeO₂ glass behaves in a similar manner to silica glass.

Section snippets

Experimental procedure

Germanium dioxide glass was prepared from 99.98% purity germanium dioxide powder. A small quantity of water has a disproportionately large influence on glass properties and germanium dioxide glass has a strong affinity for water. In order to reduce the water content in the glass, the powder was dried in a platinum crucible in thin layers at 950 °C for 0.5 h under dry air [8]. Additional layers of powder were added to the crucible and the heat-treatment was repeated until approximately 40 g of

Results

Fig. 1 shows the IR absorption spectra for glass samples prepared with and without prior drying procedure, indicating that substantial reduction in the water content in the glass is achieved by the drying process of the powder [8]. Both glass samples had the same thickness of approximately 0.6 mm. The absorption peak at ∼3560 cm⁻¹ is due to the hydroxyl group [8]. The absorbance, A, is then directly related to the concentration of hydroxide by the equation A = εcd, where A is absorbance and ε, c,

Discussion

The reflection peak for GeO₂ glass at 916 cm⁻¹ in wavenumbers is known as the germania structural band from literature [3], [4], [5], [6]. As can be seen in the paper by Venediktov et al., the vibrational spectrum for GeO₂ glass and SiO₂ glass exhibit similar spectra with peak wavenumbers shifted by the bond strength (k) and reduced mass (m) difference between Si–O and Ge–O bonds, $υ = \frac{1}{2 π} \sqrt{(\frac{k}{m})}$ . The 1116 cm⁻¹ reflection band in SiO₂ glass is known to be due to asymmetric stretching in the Si–O–Si

Conclusion

It was shown that the fictive temperature of GeO₂ glass can be determined by measuring the IR peak wavenumber of the GeO₂ glass structural band and using a pre-determined calibration curve. In spite of the anomalous behavior of the vibrational and some mechanical properties, refractive index and density exhibited the behavior of normal glasses.

Acknowledgement

This research was supported by NSF Grant DMR-0352773.

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Journal of Non-Crystalline Solids

Abstract

Introduction

Section snippets

Experimental procedure

Results

Discussion

Conclusion

Acknowledgement

References (14)

J. Non-Cryst. Solids

J. Non-Cryst. Solids

J. Non-Cryst. Solids

J. Non-Cryst. Solids

J. Appl. Spectrosc.

J. Phys. Chem. Glasses

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In situ high pressure and high temperature Raman studies of (1-x)SiO <inf>2</inf>xGeO<inf>2</inf> glasses

Temperature Dependence of the Thermo-Optic Coefficient of SiO<inf>2</inf> Glass

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