Electrical property investigations and microstructure characterization of a nuclear borosilicate glass ceramic

The electrical properties of a borosilicate glass ceramic used as a conditioning matrix for nuclear waste management are investigated by impedance spectroscopy over frequency and temperature ranges from 1 Hz to 1 MHz and from room temperature to 500 °C respectively. The microstructure of the glass ceramic was studied by scanning electron microscopy which revealed a phase separation phenomenon. The single circle arcs obtained from a complex impedance plot ($-Z^{\text{'}\text{'}}\left(\omega \right)vs{Z}^{\text{'}}\left(\omega \right)$) indicate a pure ionic conduction mechanism and no Maxwell-Wagner-Sillars (MWS) polarization effect. The dependence of ac conductivity on frequency follows Jonscher's power law (known as the UDR: Universal Dielectric Response) very well. The plateau at low frequency corresponding to dc conductivity (${\sigma }_{dc}$ or ${\sigma }_0$) is mainly associated with the long-distance motion of alkali ions and increases linearly with temperature in Arrhenius coordinates. Scaling of both conductivity and dielectric properties were performed to avoid electrode polarization contribution and to provide better understanding of the relaxation behaviour in this sample. The master curves obtained from Summerfield scaling and normalized peaks ($Z^{\text{'}\text{'}}\left(\omega \right)/Z_{max}^{\text{'}\text{'}}$ and $M^{\text{'}\text{'}}\left(\omega \right)/M_{max}^{\text{'}\text{'}}$) formalism suggest a conductivity due to short and long range mobility for the lowest temperatures and only a long-range mechanism associated with a non-Debye relaxation process at higher temperatures.