Dielectric properties are strongly dependent on crystallization conditions, which determined the amount of SrTiO3 and secondary crystalline phases and the microstructure of the glass ceramics. Earlier reports confirm that the crystallization of the SrTiO3 phase in borosilicate (without an alkali oxide additive) as well as in aluminosilicate glassy matrix is found to be complex and difficult. Glass ceramics with varying amounts of alkali oxide (K2O) have been prepared in the strontium titanate borosilicate glass system. The glasses were crystallized in the temperature range 1073-1325 K. It is observed that the pure strontium titanate (SrTiO3) phase can be crystallized at higher temperature by choosing an optimum amount of alkali oxide (K2O). Dielectric characteristics of glass ceramic samples were measured with respect to frequency (0.1 kHz to 1 MHz) and temperature (300 to 500 K). The value of the dielectric constant is higher when Sr2B2O5 crystallizes as a primary phase while it decreases significantly when SrTiO3 crystallizes as a major crystalline phase. The temperature coefficient of the dielectric constant (TCε) becomes negative as the SrTiO3 phase crystallized out in the glass ceramics and the value of the dielectric constant increases with a higher crystallization temperature and time which finally decides the amount of the SrTiO3 phase. Attempts have also been made to correlate the observed dielectric behavior with the electrical contribution of various crystalline phases, residual glassy matrix, crystal-glass interface region and electrode contribution using the impedance spectroscopic technique.

Keywords: Borosilicate glass, Glass ceramics, Perovskite, Dielectric and impedance