Ionic transport in nano- and micro-crystalline (1-x)Li2O:xB2O3 composites was studied by using impedance spectroscopy. In nanocrystalline samples (grain size of about 20nm), the ionic conductivity increased with increasing B2O3 content; up to a maximum value at x = 0.5. The ionic conductivity vanished above x = 0.92. In microcrystalline samples, (grain size of about 10μm), the ionic conductivity decreased monotonically with the x-value and vanished above x = 0.55. The markedly different behaviours were explained in terms of a percolation model which assumed the occurrence of enhanced conductivity at the interfaces between insulating and conducting phases in both materials, and took account of the differing grain sizes.

Nanocrystalline Versus Microcrystalline Li2O:B2O3 Composites: Anomalous Ionic Conductivities and Percolation Theory. S.Indris, P.Heitjans, H.E.Roman, A.Bunde: Physical Review Letters, 2000, 84[13], 2889-92