Structure and dielectric properties of Ba1−xSrxZnTi7O16 hollandite ceramics

Abstract

Hollandite-type Ba1−xSrxZnTi7O16 (x=0, 0.2, 0.4, 0.6, 0.8, and 1) ceramics have been synthesized by the conventional solid-state ceramic route. The phase purity and microstructure of these compositions have been characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis shows that an increase in strontium concentration in the A-site causes pairing of vacant tunnel sites, and hence the structure becomes unstable due to the collapse of the tunnel walls. The dielectric properties such as dielectric constant (er), loss tangent (tan δ), and temperature variation of dielectric constant (τer) have been measured up to the 13 MHz region. The present study shows that zinc hollandites have relatively high dielectric constant and low loss tangent. The temperature variation of dielectric constant studies reveal that Ba-rich compositions have high positive τer and Sr-rich compositions have high negative τer in the 0–100°C region. Proper tailor making of these compositions has been attempted to arrive at near-zero temperature variation of the dielectric constant.