Abstract
Vitreous (v) and molten (m) GeO 2 were studied by Rayleigh and Mandel’shtam–Brillouin scattering spectroscopy and high-temperature acoustics. Original measurement apparatus and procedure were used that included Bayseian deconvolution of light scattering spectra of vGeO 2 and a specially designed high-temperature (up to 1500 °C) acoustic interferometer to measure temperature and frequency dependence of ultrasonic (US) velocity and attenuation in mGeO 2. Landau–Placzek ratios for vGeO 2 were found optically (from the light scattering spectrum) and acoustically (through the Schroeder’s formalism). Dispersion of optical and other physical parameters of vGeO 2 found by many authors is explained by the existence of small amount of GeO in the samples. It means that properties of vGeO 2 are under the influence of redox synthesis conditions controlling the GeO 2 ↔ GeO and coordination [GeO 4] ↔ [GeO 6] equilibrium in vGeO 2. Measurements of temperature dependencies of longitudinal ultrasonic velocities in mGeO 2 and in the PbO–GeO 2 glass melts as a function of PbO concentration shows existence of ‘water-like anomaly’ in mGeO 2 and in liquid germanates with the rich content of GeO 2 where equilibrium sound velocity increases with the temperature.
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