Preparation And Properties For Lead-free Na_0.5Bi_0.5TiO₃-BaTiO₃ Piezoelectric Ceramics

In this paper, the NBT-BT lead-free piezoelectric ceramics were prepared by solid phase method, and the impacts of sintering process on the structures and properties of piezoelectricity were systematically studied. Doping experiments were gone along with NBT-BT system to improve their dielectric and piezoelectric properties. Finally, we used the materials with merit performance in gelcasting process, including drying process on NBT-BT system, and we also compared it with the sample using solid phase synthesis of the same ceramics.The density, dielectric and piezoelectric properties of NBT ceramics under the different sintering processes were investigated. The samples calcined at 870℃can be denser with better dielectric and piezoelectric properties. Particle size analysis and properties indicate that the impact of particle size under increased calcining temperature is little, which can be used to wet preparation of raw materials. Then a small amount of BaTiO₃ was added with NBT to form NBT-BT solution. Based on piezoelectric and dielectric properties of the XRD analysis, we know that when x=0.06 the (1-x) Na_0.5Bi_0.5TiO_3-xBaTiO₃ crystal structure appear rhombohedra to tetragonal phase transformation. In order to improve the dielectric and piezoelectric properties, the addition of the third elements were employed to the NBT-BT system. Pre-synthesized Ba (Cu_0.5W_0.5) O₃ was put in it, and the grains are in a relatively uniform distribution. Mn-doped samples show a significant loss in dielectric loss of 1.0 %,and a rise in piezoelectric constant of 163 pC/N. With CeO₂ doping, the density of NBBT6 gradually increased, the dielectric loss has little effect. The properties showed that d₃₃=159 pC/N, kp=0.31. The gelcasting process of NBT-BT ceramics was also investigated. The samples with the pH of alkaline, dispersant dosage of 0.8 wt%, and solid levels during 40⁶0 wt% in plasma viscosity would be appropriate for high solid content, low viscosity slurry. In contrast with the SEM using solid synthesis of ceramic, we can see that the ceramic adobes after liquid pretreatment were denser, the grain size and piezoelectric properties equaled with the solid method, and the dielectric properties increased slightly, and the dielectric loss was significantly reduced.