The Debye–Waller factor approaching the glass-transition temperature in phosphate glasses

The temperature dependence of the mean square displacement, 〈u2〉, calculated by elastic neutron scattering for two phosphate glasses, (AgI)x(AgPO3)1−x with x = 0.3, 0.55, is analysed. The studied samples are probed in a wide range of temperatures going from a few tens of K up to the glass transition temperature and well into the undercooled liquid state. In the low temperature regime a solid like behaviour appears, showing a linear temperature dependence of the Debye–Waller factor, while around Tg the onset of a pronounced increase of 〈u2〉 is observed. The temperature dependence of the normalized elastic intensity and the drawn out Debye–Waller factor are fitted and analyzed by the theoretical previsions of Mode Coupling Theory finding a good agreement.