Structure and Dielectric Properties of Pure and Zinc Oxide-Doped Barium Titanate

Abstract The effects of zinc oxide addition and sintering parameters on the structure and dielectric properties of barium titanate are observed. Different percentage of ZnO ranging from 0.30 to 1 wt. % is doped in barium titanate. Both the doped and undoped samples are sintered at temperatures ranging from 1250°C to 1325°C at different soaking times. The amount of densification of the doped and undoped samples is measured in terms of percentage theoretical density. Grain size and microstructural analysis is performed by a scanning electron microscope (SEM). Lattice parameters and tetragonality of doped and undoped barium titanate are calculated from x-ray diffraction pattern obtained from x-ray diffractometer (XRD) test. Dielectric properties of the samples are measured by an impedance analyzer. It is found that all the doped samples obtain their maximum percentage theoretical density at a lower sintering temperature compared to the undoped sample. SEM study reveals that the doped samples always show smaller grains compared to the undoped sample. Significant grain growth is observed in all of the samples at sintering temperatures above 1300°C. The evidence of surface melting is observed in 1 wt. % ZnO-doped sample soaked at 1325°C for 2 h. The presence of liquid at that sintering condition is explained by the doping mechanism of Zn2+ in BaTiO3. Correlation among the grain size, tetragonality, and dielectric properties of the doped and undoped samples are also discussed.