Fabrication and Electrical Properties of Multilayer Ceramic Actuator Using Lead-Free (Bi1/2K1/2)TiO3

A prototype of a multilayer actuator (MLA) was fabricated using (Bi1/2K1/2)TiO3 (BKT) ceramics as active layers and Ag–Pd (7:3) as inner electrodes. Then, their microstructures and electrical properties were investigated. From the scanning electron microscope (SEM) observation, the thickness of the BKT active layers between electrodes was estimated to be approximately 60 µm for the body co-fired at 1045 °C for 10 h. Also, SEM images showed homogeneous and dense microstructures on the BKT active layers. Additionally, the interface between BKT and the Ag–Pd electrode was clearly distinguished and there are no significant signs of reaction or diffusion between them at least from the SEM micrographs. The resistivity ρ of BKT sample co-fired at 1045 °C for 10 h was about 1011 Ω·cm on average, which is sufficient for applying a high DC electric field to the sample. From the measurement of the field-induce strain S under unipolar driving at 100 kV/cm, a large strain of 0.14% at 100 kV/cm was obtained and the longitudinal dynamic displacement was 1 µm at the same electric field. The normalized d 33 * was calculated to be 138 pm/V, which is similar to that in the bulk samples. This result indicates that the BKT-based multilayered prototype efficiently functioned under unipolar driving up to 100 kV/cm.