HIGH-TEMPERATURE INTERNAL-FRICTION PEAK OF NA2O-CENTER-DOT-2CAO-CENTER-DOT-3SIO(2) GLASS

The internal friction of Na2O . 2CaO . 3SiO(2) glass was measured with an inverted torsion pendulum in the 0.35-0.95 Hz frequency range. A low-temperature peak and a high-temperature peak were observed. The temperature dependence of high-temperature peak frequency was expressed as f = (6.49 +/- 0.18) X 10(14) exp{(-175 +/- 7 kJ mol(-1))/RT} Hz. The activation energy for calcium diffusion in the glass, with the same composition as that used in the present study, was also calculated from the diffusion coefficients below the glass transformation temperature. The temperature dependence of the diffusion coefficients of calcium was expressed as D = 1.61(-0.48)(+0.69) X 10(-5) exp{(-185 +/- 21 kJ mol(-1))/RT} m(2) s(-1). The activation energy for the high-temperature peak agreed with that for calcium diffusion calculated from the data below the glass transformation temperature within experimental errors of these results. It is concluded that the high-temperature peak of Na2O . 2CaO . 3SiO(2) glass is caused by the movement of calcium ions under stress.