Dielectric property and polarization mechanism of sodium silicate glass in GHz-THz range

Abstract

Glass is a candidate of dielectric materials for high-frequency communication technologies, and it is important to clarify the dielectric function of glass in GHz-THz range. In this study, the complex permittivities of silica glass and sodium silicate glasses were measured at 0.5-15 THz using terahertz time-domain spectroscopy and terahertz spectroscopic ellipsometer systems. The dielectric permittivity and loss of silica glass were extremely low in the GHz band, whereas those of sodium silicate glasses were relatively high in the GHz band. The dielectric dispersion at frequencies lower than 9 THz became larger with increasing Na content, and the dispersion greatly affected the dielectric permittivity and loss in the GHz band. Molecular dynamics simulations indicated that vibrations and migrations of Na ions occur in the frequency range of GHz to THz, and the dielectric dispersion at frequencies below 9 THz is due to the vibrations and migrations of Na ions, which are easily moved by an electric field. These results suggested that glass materials with a low amount of alkali metal ions are required when glass materials are applied as a high-frequency dielectric material.