High-Performance Ceramics V

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Authors: Ye Jing Dai, Xiao Wen Zhang
Abstract: In this paper, 0.95K0.5Na0.5NbO3-0.05LiTaO3 ceramics were synthesized by conventional mixed-oxide technique. To clarify the optimal sintering condition, three kinds of different temperature conditions were used. It was found that the samples sintered near 1130 °C had the best piezoelectric properties (d33~155 pC/N). In addition, sintering aid such as K5.4C1.3Ta10O29 was investigated to confirm whether it really benefited to the sintering process and increased the piezoelectric property of ceramics.
Authors: Tatsuro Hotta, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: (Na0.5K0.5)NbO3-LiNbO3 (LNKN) is a lead-free ceramics, reported to show the maximum piezoelectric property when the Li content is 6.0 mol%. The temperature dependence of the spectra was measured for LNKN in the 4.0-8.0 mol% range of Li content by using Raman scattering. The stretching and bending mode of NbO6 octahedron especially changed the form and/or frequency of the spectrum with increasing Li content from 5.0 to 6.0 mol%. The range of this composition is corresponding to the composition with the maximum piezoelectric property.
Authors: Ming He Cao, Wan Qiang Wang, Zhi Yong Yu, Hua Hao, Han Xing Liu
Abstract: (1-x)(K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3-xSrTiO3 (KNNT-ST) lead free piezoelectric ceramics have been synthesized by a solid state reaction method. The effect of SrTiO3 content on the piezoelectric properties, sintering behavior and microstructure of (1-x) KNNT-x ST ceramics was investigated. The experimental results showed that the addition of SrTiO3 can restrain the volatilization of Na ions and K ions and improve relative density of the samples. A morphotropic phase boundary between orthorhombic and tetragonal phases is found in the composition range of 0.03
Authors: Kong Jun Zhu, Jin Hao Qiu, Koji Kajiyoshi, Kazumichi Yanagisawa
Abstract: Hydrothermal method was used to synthesize the Na(TaxNb1-x)O3 (x = 0.1-0.5) powders with the addition of isopropanol. The phases of the obtained powders were confirmed by XRD. The morphology and particle size were observed by FE-SEM. The specific surface areas were measured by multipoint BET technique. The presence of water and organic group were determined by (FT-IR) spectroscopy. The results indicate that the pure Na(TaxNb1-x)O3 (x = 0.1-0.5) powders with perovskite structure and fine particles were successfully synthesized by hydrothermal method at 240 °C for 8 hours with the addition of isopropanol.
Authors: Min Soo Kim, Sin Woong Kim, Soon Jong Jeong, Jae Sung Song
Abstract: Dense Li2O excess (Na0.49K0.49Li0.02)(Nb0.8Ta0.2)O3 [NKLNT] ceramics were developed by conventional sintering process without any special technique. The electrical properties of NKNLT ceramics were investigated as a function of Li2O concentration. When the sample sintered at 1050 oC for 4 h with the addition of 1 mol% Li2O, electro-mechanical coupling factor (kP) and piezoelectric coefficient (d33) were found to reach the highest values of 0.42 and 260 pC/N, respectively.
Authors: Li Jin Xie, Gao Jie Xu, Zhi Xiang Li
Abstract: Anisometric KSr2Nb5O15 (KSN) particles were synthesized by molten salt method with SrCO3, Nb2O5 and KCl as raw materials. With K2CO3, SrCO3 and Nb2O5 starting materials, KSN lead-free piezoelectric ceramics were prepared by conventional ceramics technique and reactive templated grain growth (RTGG) method, respectively. In the RTGG process, green compacts were fabricated by tapecasting using anisometric KSN as template particles. The KSN particles prepared by molten salt method were rodlike in shape and dense. The KSN ceramics prepared by RTGG not only had higher degree of grain orientation but higher sintered density compared with that prepared by solid-state reaction.
Authors: Wei Zhao, He Ping Zhou, Yong Ke Yan, Dan Liu
Abstract: A lead-free piezoelectric ceramic binary system based on bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT)-bismuth potassium titanate (Bi0.5K0.5)TiO3 (BKT) was synthesized by conventional mixed-oxide technique. The XRD analysis showed that the rhombohedral-tetragonal morphotropic phase boundary (MPB) of the Bi0.5 (Na1-xKx)0.5 TiO3 system was in the composition range of x = 0.16 ~ 0.20. In addition, the piezoelectric properties of this system were also investigated. It was indicated that the piezoelectric properties are better with the compositions near the rhombohedral phase within the MPB than the compositions near the tetragonal phase.
Authors: Zhi Wu Chen, Zhen Ya Lu, Jian Qiang Hu
Abstract: Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.94(Ba1-xSrx)0.06TiO3 (abbreviated as BNBST-100x, with x ranges from 0.02 to 0.1) have been investigated. Effects of amount of Sr-substitution on the electrical properties and crystal structure of the ceramics were studied. The BNBST-100x ceramics sintered at 1200°C for 2h in air have high density around 5.69~5.75g/cm3. X-ray diffraction (XRD) analysis shows that all of the BNBST-100x ceramics have pure perovskite structure. At high amount level of Sr-substitution, the crystal structure of the samples changes from rhombohedral to tetragonal symmetry. Piezoelectric and dielectric measurements reveal that Sr-substitution amount within a certain range will lead to the increase of piezoelectric coefficient (d33), electromechanical coupling factor (kp), and relative dielectric constant (ε33 T/ε0). At 6 mol% Sr-substitution level, the d33 and kp of the ceramics reach maximum, with values of 168 pC/N and 34%, respectively.
Authors: Jian Qiang Hu, Zhi Wu Chen
Abstract: Bi2O3 doped (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT6) lead-free piezoelectric ceramics were fabricated by a conventional sintering technique. The effects of Bi2O3 on the piezoelectric properties and microstructures of the doped BNBT6 were investigated. X-ray diffraction analysis showed that a solid solution was formed when Bi2O3 diffused into BNBT6 lattice and the crystal structure of the sintered hybrid changed from rhombohedral to tetragonal symmetry with increasing Bi2O3 amount. Piezoelectric and dielectric properties measurements revealed that doping Bi2O3 within a certain range enhanced the piezoelectric coefficient (d33), electromechanical coupling factor (kp), relative dielectric constant (ε33 T/ε0), and dielectric loss (tanδ). When 3mol% Bi2O3 was doped, both d33 and kp of the ceramics reached their maxima, 165pC/N and 24%, respectively.
Authors: Chun Huy Wang
Abstract: Many lead-free materials, such as Bi-based compounds, BaTiO3 or alkaline niobate compound, have been intensively studied. The microstructure and characteristics of BaTiO3 ceramics are significantly influenced by addition of 4PbO-B2O3. Under low sintering temperatures, the grain growth of BaTiO3 ceramic is enhanced by capillary action, rearrangement and solution-reprecipitation of the liquid phase. At high sintering temperatures, exaggerated grain growth of BaTiO3 ceramic is restrained by the presence of a liquid phase. The theory of grain growth in the presence of a liquid phase is examined in terms of the equation Rn = k× t. The grain growth kinetic exponent, n, has an inverse relationship with the rate of grain growth. With suitable amounts of glass frit and an optimized sintering temperature, the density is enhanced and the values of the dielectric and piezoelectric properties are improved.

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