Preparation Of Lead-free Piezoelectric Ceramics Research Articles

Young’s modulus and damping of partially sintered potassium sodium niobate (KNN) ceramics and its temperature dependence determined via the impulse excitation technique (IET)

Potassium sodium niobate (KNN) is suitable for the preparation of lead-free piezoelectric ceramics, and thus the elastic properties and damping behavior should be reliably known for practical applications. In this work we compare partially sintered KNN ceramics prepared by uniaxial and conventional sintering from three different KNN powders and show that the impulse excitation technique (IET) is perfectly suited to determine Young’s modulus at room temperature as well as the temperature dependence of Young’s modulus and damping (heating-cooling cycles with maximum temperature 800 °C). Room temperature values of the effective Young’s modulus of partially sintered KNN ceramics are below the predictions for convex pores and above a recently published numerical benchmark relation for concave pores. The phase transition temperatures determined by the IET are 160–190 °C for the low-temperature orthorhombic-tetragonal / tetragonal-orthorhombic transition and 388–412 °C for the high-temperature tetragonal-cubic / cubic-tetragonal transition, with hysteresis 12–25 K.

Kirigami-Origami-Inspired Lead-Free Piezoelectric Ceramics.

Kirigami- and oirigami-inspired techniques have emerged as effective strategies for material structure design; however, the use of these techniques is usually limited to soft and deformable materials. Piezoelectric ceramics, which are typical functional ceramics, are widely used in electronic and energy devices; however, the processing options for piezoelectric ceramics are limited by their brittleness and feedstock viscosity. Here, a design strategy is proposed for the preparation of lead-free piezoelectric ceramics inspired by kirigami/origami. This strategy involves direct writing printing and control over the external gravity during the calcination process for the preparation of curved and porous piezoelectric ceramics with specific shapes. The sintered BaTiO3 ceramics with curved geometries produced using this strategy exhibit a high piezoelectric constant (d33 = 275 pCN-1 ), which is 45% higher than that of conventionally sintered sheet ceramics. The curved structure of the ceramics is well-suited for use in the human body and itwasdetermined that these curved ceramics can detect pulse signals. This strategy can be applied in the large-scale and low-cost production of other piezoelectric ceramics with various curved shapes and provides a new approach for the preparation of complex-shaped ceramics.

Ceramic synthesis of 0.08BiGaO3–0.90BaTiO3–0.02LiNbO3 under high pressure and high temperature**Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).

In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100–1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance.

Synthesis and Characterization of (K0.5Na0.5)NbO3 Piezoelectric Ceramics Prepared Using K5.70Li4.07Nb10.23O30 as a New Sintering Aid

K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramics containing 1 mol% ZnO (KNNZ) were prepared by optimizing the sintering conditions using the newly developed K5.70Li4.07Nb10.23O30 (KLN) as a sintering aid. The phase structure and electrical properties of the KNNZ ceramics were investigated as a function of the KLN concentration. The results show that a small amount of KLN was incorporated into the lattice and formed a single-phase perovskite structure. The KLN modification lowered the phase transition temperature of the orthorhombic–tetragonal structure and increased the Curie temperature. Interestingly, an appropriate amount of KLN can simultaneously improve the sinterability of the KNNZ ceramics and the ferroelectric and piezoelectric properties. Good piezoelectric and dielectric properties (piezoelectric constant, d 33 = 131 pC/N; planar coupling coefficient, k p = 0.42; dielectric constant, ϵ r = 634; and mechanical quality factor, Q m = 20) were obtained for the KNNZ ceramics doped with 1 mol% KLN. Therefore, KNNZ + 1.0 mol% KLN ceramics containing an appropriate amount of KLN are good candidate materials for the preparation of lead-free piezoelectric ceramics.

Preparation of Lead-Free Piezoelectric Ceramics from (1−x)BNLT-xBT Ceramics System

The preparation of Lead-free piezoelectric ceramics of lanthanum doped bismuth sodium tinanate (Bi 0.487 Na 0.487 La 0.017 TiO 3 : BNLT) and barium titanate (BaTiO 3 : BT) have been carried out in the system of (1−x)BNLT-xBT where x = 0, 0.2, 0.4, 0.8 and 1.0. The BNLT and BT powders were produced separately using conventional method and they were then mixed by following above ratios. Physical, dielectric and piezoelectric properties were also observed. The optimum sintering temperatures of ceramics are in the range of 1100°C to 1150°C with a soaking time for 2 hours. The optimum conditions in terms of microstructure, physical, dielectric and piezoelectric properties were found in the (1−x)BNLT-xBT ceramic with x = 0.2.