Investigating the effect of annealing temperature on the dielectric properties of zinc oxide ceramic

Zinc oxide (ZnO) ceramic is of interest due to its unique properties such as semiconductor, photocatalytic, biocompatibility and high dielectric constant. This research investigates the effect of annealing temperature on the dielectric properties, microstructure, and electrical resistance of ZnO ceramics. ZnO samples, after sintering at 1250°C, were annealed at temperatures of 850, 950, and 1050°C for 4 hours. X-ray diffraction analysis results showed that annealing reduces microstrain in the samples and increases the size of crystallite. No significant differences were observed in the size and morphology of the grains in the annealed and non-annealed samples. Annealing resulted in a significant decrease in the dielectric constant and dielectric loss of ZnO ceramics. The sample annealed at 950°C had the lowest dielectric constant and dielectric loss. Annealing at 950°C reduced the dielectric constant of ZnO ceramic from 111,000 to 35,000 and the dielectric loss from 22 to 6, measured at 1 kHz. The reduction in electrical losses may be attributed to the decrease in microstrain and the increase in crystallite size. The conductivity of annealed samples was lower than ZnO ceramic. Annealing caused an increase in the electrical resistance of the grain and grain boundary of ZnO ceramics. A significant increase in the electrical resistance of the grain boundary may indicate a decrease in the concentration of oxygen vacancies, which leads to a decrease in the dielectric constant of ZnO ceramics.