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).
456
Authors: P.R. Chalker, K.M. Berggreen, A.T. Clare, J. Singh, C.J. Sutcliffe
Abstract: This paper investigates the rapid prototyping of components from ceramics. Selective laser sintering of barium titanate powder has been investigated as a potential route to manufacturing freeform electro-ceramic based components. Raman spectroscopy has been used to investigate the effect of laser power and oxygen partial pressure on the phase and composition of the sintered material. It is shown that the sintering laser power strongly influences the composition. As the laser power is increased during sintering, the Eg mode of anatase becomes evident at 640 cm-1. When the oxygen partial pressure in the sintering atmosphere is reduced from 19% to 0.2% the whole depth of the powder bed sampled by Raman spectroscopy resembles bulk anatase.
1
Authors: Sen Wang, Zhi Hui Li, Xin Liu, Huan Zhang
Abstract: Anti–reducing effect of CaO in barium titanate based ceramic materials sintered at reducing atmosphere and the structure development of the materials has been studied in this paper.The results show: Addition of CaO in barium titanate based ceramic will keep resistivity of the sample sintered at reducing atmosphere at a high level. The resistivity of the materials increase with the increasing of CaO, and the resistivity keep in constant after the amount of CaO excess 3mol%. In the sample with sintering aid of SiO2 and BaO-excess, introducing of CaO may improve the resistivity of the materials obviously. A slight new phase formation was found in the BaO-excess sample, but no new phase formation was found in the non BaO-excess sample. If there is sintering aid of SiO2 in the sample, CaO may accelerate liquid phase film formation at the surface of grains, which will suppress the diffusion of oxygen in the grains to the environment.
2457
Authors: Mônica C. de Andrade, Geysa N. Carneiro, Elizabeth L. Moreira, Jorge C. Araújo, Valéria C.A. Moraes
Abstract: Solid-state reactions were used to synthesize pure and doped barium titanate powder. Barium titanate formation with tetragonal perovskite structure was detected by X-ray diffraction and occurred at a temperature above 700°C for pure powder and 500°C for doped powder. However, quite crystalline samples were observed only at 800oC and 600°C for pure and doped barium titanate, respectively, what made the refinement of the synthesized powders possible. They were characterized by X-ray diffraction and Fourier transform infrared spectroscopy and scanning electron microscopy. X-ray diffraction data was analyzed by using the Fullprof Rietveld refinement approach, Thompson-Cox-Hastings pseudo-Voigt with function. The refinement method was effective in the study of the temperature influence on the microstructure of the analysis of pure and doped barium titanate.
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