Bulk and local dynamics in glass-forming liquids: A viscosity, electrical conductivity, and NMR study of aluminosilicate melts - art. no. 024206

The viscosity and electrical conductivity and the Al-27 spin-lattice :relax ation time have been measured for two calcium aluminosilicate liquids or gl asses. At high temperature, the relaxation times for the three processes ar e the same to within experimental errors. This similarity points to a coupl ing between the rate of Al-O bond exchange and the structural relaxation in volved in viscous flow, which also controls the motion of Ca ions that is a ssociated with electrical conductivity. Near the glass transition, decoupli ng of Ca motion is indicated by the fact that the characteristic time for c alcium hopping is much shorter than the structural relaxation time. For the quenched glass, the electrical conductivity is then much higher than would be predicted from extrapolation of the high-temperature equilibrium data f or the melt.