Microstructure and broadband dielectric properties of Zn2SiO4 ceramics with nano-sized TiO2 addition

摘要

Zn2SiO4 ceramics with nano-sized TiO2 addition (ZST) were synthesized by conventional solid state method. The association between the new composite's microstructures and dielectric properties reveals that reduced pores, increased density and average grain sizes with increasing sintering temperatures, have contributed to the increased permittivities at kHz and microwave bands; the decrease of the permittivities at 1275 degrees C is due to the form of twin planes. At the terahertz band, the competition of generating oxygen vacancies and forming them into twin crystallographic shear planes dominates the change of permittivities: the crystallographic shear planes decrease the permittivity at the sintering temperature 1225 degrees C and 1250 degrees C, and the high-rate generation of oxygen vacancies at 1275 degrees C increases the permittivities. The ZST ceramics demonstrate stable permittivity and low dielectric losses ( < 10(-3) from 10 kHz to microwave band; and < 10(-2) at THz range); and the temperature coefficient of resonant frequency is optimized to close zero. These advanced dielectric properties and low sintering temperature (< 1300 degrees C) provide the ZST ceramics great potential in designing microwave and THz devices.