Effect of Nb doping on sintering and dielectric properties of PZT ceramics

The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT) in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4mol% Nb-doped PZT (PZTN) powders were successfully obtained by a solid-state reaction and calcination at 850 degrees C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD). In order to study morphology of powders, scanning electron microscopy (SEM) was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 degrees C, with a heating rate of 10 degrees C/min, and holding time of 1-6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 degrees C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (er similar to 17960) with lower Curie temperature (similar to 358 degrees C) relative to PZT (epsilon(r) = 16000 at similar to 363 degrees C) as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz) of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.