Papers by Keyword: MnCO3

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Authors: Ming Zhao, Meng Zhang, Yu Shi, Zhi Long Wang
Abstract: 0~1.5mol% MnCO3 doped ZnO-Pr6O11-Co2O3-Cr2O3 varistor ceramics were synthesized by conventional oxides mixing procedure. The effect of MnCO3 variations on the microstructure, phase constituents and electric field–current density (E-J) characteristics of the ceramics were studied by SEM, XRD examinations and standard E-J test. The result showed the electrical nonlinearity exponents and breakdown voltage of the ceramics increased from 38 and 1296V/mm of the un-doped one to 52 and 1420V/mm respectively with the addition of 0.5mol% MnCO3; meanwhile, the leak current density was reduced from 4.35μA/cm2 to 2.05 μA/cm2. Further doping MnCO3 deteriorated the overall varistor properties of the ceramics by remarkably decreasing the density of the ceramic, and the main reason causing the density drop was ascribed to the hindering effect of the well dispersed perovskite-like Pr0.95Mn0.9393O3 particles formed mainly within the ZnO grain boundary areas.
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Authors: Wen Jun Li, Tang Zhou, Liu Liu Ding, Lu Fang
Abstract: The nanostructured ZnS, CdS/CdCO3 and MnCO3 were prepared by the hydrothermal method with gravity field of 1000 /g in the oil/water system at 100-150 for 0.5h. The products were characterized by eld-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and BET method. The results showed that the ZnS samples obtained using ZnCl2 and Na2S2O3 as precursors at 100-120 for 0.5h were the polycrystalline microspheres self-assembled by the crystallites with the size of 3-25nm. The pore volume of polycrystalline microspheres decreased with the increase of the size of the applied gravity forces. The morphology of CdS/CdCO3 samples obtained at 100 for 0.5h was the flower-like structure, while the as-prepared samples at 120 for 0.5h were the nanoceramic microspheres in shape. The gravity force favors the formation of CdS/CdCO3 samples. Moreover, the MnCO3 polycrystalline flake can be obtained at 100-120 for 0.5h under gravity field of 1000 /g.
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