Jianwei Zhao,Hailan Qin,Xiaoxin Chen,Shuhui Yu,Dawei Wang
A number of CaHfO 3 modified BiFeO 3 -0.33BaTiO 3 (BF-0.33BT- x CH) lead-free piezoceramics were fabricated through the solid-state sintering method and comprehensively investigated in this work. Under the optimal sintering temperature, all compositions display a typical perovskite structure in a pseudo-cubic phase with slightly larger lattice parameters as the CH content increases. The electrical resistivity is highly enhanced due to the addition of CH. Microstructures, including the grain morphology, core-shell structure, and chemistry inhomogeneities, are demonstrated upon different BF-0.33BT- x CH compositions. In particular, the core-shell structures with non-uniform element distributions in the compositions can be eliminated by adding sufficient CH content ( x > 0.05). The highest saturation polarization (40.1 μC/cm 2 ), remnant polarization (26.8 μC/cm 2 ), and converse piezoelectric coefficient (290 pm/V) are achieved in the BF-0.33BT-0.01CH piezoceramic, which are significantly enhanced in comparison with the undoped BF-0.33BT piezoceramic. With further increasing the CH content, the piezoelectric properties of BF-0.33BT- x CH ceramics decline rapidly, and they start to exhibit characteristics of relaxor ferroelectrics.
On the road of lead-free piezoelectric ceramics into practical applications, the study of Ni-internal-electrode (K, Na)NbO 3 -based (KNN-based) multilayer actuators (MLAs) is an important part, possessing the advantages of environmentally friendly and low cost. The Ni-internal-electrode KNN-based MLAs with different layer numbers and layer thicknesses were fabricated via the tape casting method and sintered in the reducing atmosphere. The piezoelectric layers consist of the main KNN-based phase and a trace amount of second phase Mn 4 Nb 2 O 9 . The element diffusion between the Ni electrodes and KNN-based grains is tiny, indicating that Ni is suitable for co-firing with KNN-based ceramics. After sintering, the compressive stress perpendicular to the thickness direction and the “relative tensile stress” parallel to the thickness direction are retained in the MLAs, bringing influences on the piezoelectric and dielectric properties of KNN-based materials. Compared with the bulk ceramics, the prepared MLAs significantly reduce the driving voltages and increase the displacement outputs, which are more applicable to the scenarios of miniaturization and portability. Particularly, the 46-layer actuator shows high displacements of 1580 and 2737 nm under the voltages of 100 and 200 V, respectively. However, the inverse piezoelectric coefficient d 33 * for each layer of MLAs is still lower than that of the bulk ceramics, indicating that the piezoelectric properties of the KNN-based materials are suppressed. To give full play to the piezoelectric properties of KNN-based materials, more attentions should be paid to the design of reasonable electrode structure and the development of internal electrode paste for MLAs.
危险品化学品经营许可证（带存储）