2012 Volume 52 Issue 10 Pages 1740-1749
The temperature and the frequency dependencies of velocities and absorption coefficients of ultrasonic waves have been measured on molten alkali silicates (33(mol%)M2O–67SiO2 (M = Na and K)) using the pulse transmission technique. The velocities and the absorption coefficients have been determined by the Fourier transform of ultrasonic pulses. It has been found that the velocities, c, increases with decreasing temperature, while the absorption per wavelength, αλ, increases and then decreases with decreasing temperature. It has also been found that the c and αλ values are identical irrespective of frequencies above ca. 1400 K for 33Na2O·67SiO2 and ca. 1500 K for 33K2O·67SiO2, respectively, while dispersion, i.e., frequency dependency, appears below these temperatures. The dispersions of acoustic properties have been successfully interpreted using a structural relaxation model.