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In this study, the application of a 28 GHz microwave sintering process was attempted for the sintering of lead zirconate titanate (PZT) materials and sintering conditions were thoroughly investigated. Microwave sintering offers advantages over conventional technologies, such as repression of grain growth due to rapid heating, and improvement of microstructure due to internal heating. As a result, the sintering time of PZT materials using a 28 GHz microwave was reduced to 1/10 of the time needed for the conventional process, with improvement of material properties such as the electromechanical coupling factor and dielectric constant. Moreover, the performance of actuators fabricated by the microwave sintering process was evaluated in a vibration test and compared with the performance of actuators fabricated using conventional technology; the performance superiority was confirmed.

Piezoelectric materials play an important role in smart material and structural systems, and high-performance piezoelectric actuators with larger force and displacement output are in demand. It was shown in our previous work that the hybrid sintering process using a 28 GHz microwave technique and hot pressing offers advantages over conventional technologies reference. It was also confirmed that the maximum achieved value of piezoelectric constant d 31 of the specimens of the hybrid-sintering process is approximately 360×10-12 m/V, which is about 38% larger than 260×10-12 m/V, the d 31 of the conventionally sintered specimens. In this study, the material properties, including electromechanical coupling factor, Young's modulus, frequency constant, Curie temperature and dielectric constant, of the specimens fabricated with the microwave sintering process were further investigated for different sintering temperatures. The Curie point T c decreases, but the dielectric constant ε r at T c increases with the grain size of specimens for all sintering methods. The influence of grain size on T c and ε r can be attributed to the residual stress induced by the lattice mismatch between the cubic phase and the tetragonal-rhombohedral mixed phase.

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Hamamatsu-shi 432-8561 Lead zirconate titanate ceramics (PZT), PbZrxTi1-xO3 (0.12•…x•…0.87), were analyzed by X-ray photoelec