EXPERIMENTAL-STUDY OF THE PRECRYSTALLIZATION PROCESS IN THE AMORPHOUS FAST IONIC CONDUCTOR 0.60AGI-0.25AG2O-0.15P2O5

Systematic investigations on the pre-crystallization process in the amorphous ionic conductor 0.60AgI-0.25Ag2O-0.15P2O5 have been carried out by means of ultrasonic measurements, thermal analysis, electron microscopy (SEM and TEM) and ionic conductivity experiments. The temperature dependence of the longitudinal ultrasound attenuation and velocity showed anomalous attenuation peaks and sudden unusual relative sound velocity changes near 330 and 341 K, indicating that possible structural changes and softening of interatomic bonds occurred. These are consistent with the anomalous changes of ionic conductivity of the same samples. Thermal analysis revealed that such anomalous changes are directly related to the glass transition and the microcrystalline formation, respectively. Moreover, direct evidence for the processes of crystallizations above 344 K were given from our SEM and TEM study. Therefore, it is suggested that the observed anomalous enhancements near 326 and 344 K of ionic conductivity of this amorphous fast ionic conductor is related to the destruction of the amorphous structure and the crystallization of the amorphous state.