IONIC CONDUCTION DURING PRE-CRYSTALLIZATION PROCESS IN AMORPHOUS IONIC CONDUCTOR Li2B2O4

Abstract

The temperature dependence of ionic conductivity, especially the ion transport property during pre-crystallization process in amorphous ionic conductor Li2B2O4 has been studied. When the temperature is lower than Tk(≈310℃), the ionic conduction obeys Arrhenius relation. Above the crystallization temperature Tc(≈411℃), the ion transport behaviour is dominated by the process in crystalline state. In the range Tkc, the ionic conductivity deviates from thermal excitation mechanism and is enhanced anomalously. This process is now called pre-crystallization process. It is found that the free volume model could be used to describe the ion transport properties. In pre-crystallization process there are two distinguishable steps. Below Tp(≈380℃) the ionic conductivity increase is due to the redistribution of free volume. While above Tp considerable enhancement of the ionic conductivity is caused by the in-terfacial effect between the crystallites and amorphous matrix because small amount of crystallites (less than 5%) were emerged. The pre-crystallization status of the amorphous could be remained at ambient condition by quenching the specimen to room temperature. Therefore it is possible to prepare material with higher ionic conductivity than that of pure amorphous.