Neutron scattering studies of static and dynamic correlation lengths in alkali metal borate glasses

Kojima, Seiji*; Novikov, V. N.*; Kofu, Maiko   ; Yamamuro, Osamu*

This paper reports the variation in the first sharp diffraction peak (FSDP) and the boson peak (BP) of lithium and cesium borate glasses xMO-(1-x)BO (M = Li, Cs, x = 0.08, 0.14, 0.22) investigated by elastic and inelastic neutron scattering. The different content dependences between lithium and cesium borate glasses are discussed based on the different modifications of the boron-oxide network structure by the small Li and large Cs ions. The static characteristic correlation lengths R were determined from the width of the FSDP of the static structure factor . The dynamic characteristic correlation lengths R were determined from the BP energy of the dynamic structure factor . They are close in absolute value (about 2 nm). With increasing x, R increases, while R gradually decreases with the different rate in the lithium and cesium glasses. However, their ratio, R/R increases with the content of the metal in both the lithium and cesium glasses at the same rate. The decrease in the amplitude of elastic fluctuations with the increasing x due to the increase in fragility with the increasing x might restore the correlation between R and R in the lithium borate glasses, and this tendency may be the same for the cesium borate glasses.