Authors: Michiyasu Nishiyama, Takuya Hoshina, Hirofumi Kakemoto, Takaaki Tsurumi, Satoshi Wada
Abstract: A new method for ultrafine barium titanate (BaTiO3) particles with diameters of around 5 nm is proposed. In this method, barium titanyl oxalate aqua solution with low concentration below 10-3 mol/l was used as the starting material. The droplets with a size below 3 μm were atomized with an ultrasonic vibrator, dried and thermally decomposed at higher temperatures over 300°C. In the preparation of the BaTiO3 particles, there were two parameters such as thermal decomposition temperature and precursor solution concentration. Therefore, various particles were prepared by changing these parameters. Finally, non-aggregated nm-sized BaTiO3 particles with an average diameter of 5.2 nm, despite wide size distribution from 2 to 20 nm, were prepared by using the precursor solution with 10-6 mol/l.
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Authors: Tian Wang, Xiao Hui Wang, Guo Feng Yao, Yi Chi Zhang, Xun Xun Liao, Gang Yang, Tae Ho Song, Long Tu Li
Abstract: Ultrafine-grained ceramics based on nano-scale barium titanate for BME-MLCC applications
have been prepared. Relationships of milling time, microstructures and dielectric properties have been
investigated. With processing selected carefully, the present ceramics show ultrafine grain size (180nm)
and homogeneous microstructures, well with high dielectric constant (ε25=2550), low dielectric loss
(<0.02), high resistivity, high breakdown field and X7R temperature specifications, which would be
promising materials for the next generation BME-MLCC applications.
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Authors: Huan Liu, Shu Ping Gong, Dong Xiang Zhou, Chun Fang Cheng, Zhi Ping Zheng, Yun Xiang Hu
Abstract: Dense PTC ceramics were prepared with BaTiO3 nanopowders synthesized by hydrothermal
method. BaCO3 and Ti(OC4H9)4 were used as barium and titanium sources, and Y(NO)3·6H2O as the
donor dopant respectively. The average grain size of the powders obtained after hydrothermal treatment at
160°C for 9h was about 30nm with cubic structure. Mn(NO3)2 was introduced to the as-prepared
nanopowders in order to improve the PTC effect. After sintered at 1280°C, the PTC ceramic samples
exhibited sufficient resistance jump ratio(1.086×103) around Curie temperature, the density of which was
5.81g/cm3(96.5% of the theoretical density).
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Authors: Yu Hua Feng, Tie Zheng Pan, Xiang Qian Shen, Hao Jie Song, Li Ping Guo
Abstract: Piezoelectric ceramics with appropriate curie temperatures and high dielectric and piezoelectric performances are attractive for formations of ceramic/polymer piezoelectric composites. The PSZT ceramics with compositions of 0.98Pb1.0-xBaxTi0.48Zr0.52O3-0.02PbSbO3 (x=0.14~0.24) have been prepared by a conventional solid reaction process. The ceramic structures are analyzed by X-ray diffraction and the barium substitution leads to structural changes of the tetragonal and rhombohedral phases which constitute the perovskite PSZT ceramics, and lattice distortions. The curie temperature almost linearly decreases from 226 °C to 141 °C corresponding the barium content increases from 0.14 to 0.24 in the ceramics. The dielectric and piezoelectric properties are largely influenced by the barium substitution and when the barium content at vicinity of 0.22, the piezoelectric strain constant d33 exhibits a dramatic change. It is found that as the barium content around 0.22, the PSZT ceramic specimen is characterized with a low curie temperature Tc=156 °C, and satisfied dielectric and piezoelectric properties with the relative dielectric constant εr=5873, dielectric loss factor tanδ=0.0387, piezoelectric strain constant d33=578 pC/N.
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Authors: Shuhei Kondo, Tatsuya Kita, Petr Pulpan, Chikako Moriyoshi, Yoshihiro Kuroiwa, Satoshi Wada
Abstract: Barium titanate (BaTiO3) nanoparticles were prepared by a two-step thermal decomposition method using barium titanyl oxalate nanoparticles of size 30 nm with and without dry-jet milling. Dry-jet milled barium titanyl oxalate nanoparticles (BTO-B) were well-dispersed whereas those without the dry-jet milling procedure (BTO-A) were partially aggregated. A heat annealing of obtained BaTiO3 nanoparticles at the same temperature resulted in crystallite sizes of the BTO-A derived BaTiO3 nanoparticles much smaller than those of the BTO-B derived. A mesoscopic particle structure analysis of revealed much thinner surface cubic layer thickness of the BTO-B derived BaTiO3 nanoparticles compared with the BTO-A derived BaTiO3 nanoparticles. This indicated the particle growth rate to be the most important parameter for the surface cubic layer thickness determination. A relationship between the surface cubic layer thickness and the particle growth rate was investigated precisely in this study.
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