Effects of grain size on the electrical properties of PbZr0.52Ti0.48O3 ceramics

The lead zirconate titanate composites of Zr content 52 mole% (PZT-A) were synthesized by normal sintered and hot-pressure processing methods. The dielectric constant, ac conductivity, and hysteresis were measured as a function of the grain sizes. As the grain size decreased, the maximum dielectric constant decreased and the transition temperature increased. Coarse-grained samples showed second-order phase transition but medium- and fine-grained samples showed diffuse phase transition characteristics. We calculated the diffusiveness on the medium- and fine-grained samples and we obtained diffusiveness coefficients m between 1.79 and 2.10. In ac conductivity measurement, we calculated the vacancy formation energy and the highest activation energy needed to make vacancies in the fine-grained sample. Using powder Xray diffraction, we calculated the precise lattice parameters with a = 4.0395 Angstrom and c = 4.1463 Angstrom in tetragonal systems and we concluded that PZT-A had a point group of C-4v (space group: P4mm) in the ferroelectric phase and O-h(m3m) in the paraelectric phase. From the hysteresis loop measurements, we obtained the remanent polarization and calculated the squareness of our samples as a function of grain sizes.