Ultrasound propagation in glasses in the metastable immiscibility region of the sodium borosilicate system

TLDR: In this paper, the authors measured the ultrasound wave velocity and attenuation in a series of quenched and heat-treated Na2O-B2O3SiO2 glasses and found that the attenuation of both longitudinal and shear waves below room temperature is dominated by a broad and intense loss peak.

Abstract: Measurements of ultrasound wave velocity and attenuation have been made between 1.3 K and 400 K in a series of both quenched and heat-treated Na2OB2O3SiO2 glasses. As in many other inorganic glasses, the ultrasound attenuation of both longitudinal and shear waves below room temperature is dominated by a broad and intense loss peak; the height and temperature of the peak maximum are frequency sensitive. The loss peak characteristics are consistent with a structural relaxation mechanism with a distribution of activation energies and this model is used to analyse the data. The features of the acoustic loss peak and also the absolute value and temperature coefficient of ultrasound velocity are strongly dependent on the total Na2O network modifier content of the glasses. The ultrasound wave propagation is also affected by phase-separation inducing heat treatment: a steady rise in the height of the acoustic loss peak and an upward shift in the peak temperature takes place with increasing time of heat treatment at 550°C, a finding which suggests that structural rearrangements are still occurring in the individual glassy phases even after long periods of heat treatment. It is proposed that heat treatment causes migration of Na+ ions away from BOB bonds in the B2O3 rich phase.