Xiangrong Wang

Two dielectric relaxation mechanisms observed in lanthanum doped barium strontium titanate glass ceramics

The dielectric relaxation at temperatures ranging from 100 °C to 550 °C in lanthanum-doped barium strontium titanate glass ceramics has been investigated by measurements of both dielectric temperature curve and complex impedance spectroscopy. The temperature dependence of dielectric properties reveals two regimes. In the first regime, at temperatures lower than 350 °C, the charge carrier contributed to interfacial polarization is conduction electrons. In contrast, in the second regime, at temperatures higher than 350 °C, the dielectric relaxation was attributed to the thermally activated movement of oxygen vacancies. Thus, two relaxation mechanisms could be explained on the basis of defect chemistry and impedance analysis.

Phase Development and Dielectric Properties of Barium Strontium Titanate Based Glass Ceramics

The phase development, microstructural evolution, dielectric properties and energy storage characteristics were investigated as a function of crystallization temperature in barium strontium titanate-based glass ceramics. According to the XRD study, a majority phrase (Ba, Sr)TiO3 and the minor phase BaAl2Si2O8 were formed during the crystallization. Scanning electron microscopy investigations have revealed that with increasing crystallization temperature the volume faction of crystalline phases as well as their crystalline sizes increase. In addition, as the crystallization temperature increased, the dielectric constant of the glass ceramics increased and the dielectric breakdown strength decreased. The correlation between the dielectric properties and energy storage characteristics was qualitatively discussed.