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Dong Y.-J.,Jiangsu University | Dong Y.-J.,University of Electronic Science and Technology of China | Cui F.-D.,Jiangsu University | Jiao L.,Jiangsu University | And 7 more authors.
Journal of Central South University | Year: 2013

ZnO-Bi2O3-based varistor ceramics doped with Eu 2O3 in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1 000 C for 2 h. XRD and SEM were applied to determine the phases and microstructure of the varistor ceramics. A DC parameter instrument was applied to investigate the electronic properties and V-I characteristics. The XRD analysis of Eu2O3-doped ZnO-Bi2O3-based varistor ceramics shows that the ZnO, Eu-containing Bi-rich, Zn7Sb2O12-type spinel and Zn2Bi3Sb3O14-type which is the pyrochlore phase are present. With increasing Eu2O3 content, the average size of ZnO grain firstly decreases and then increases. The grain boundary defect model was particularly used to explain the excellent nonlinearity of ZnO-Bi2O3-based varistor ceramics with the addition of 0.1 % Eu2O3 and sintered at 950 C. © 2013 Central South University Press and Springer-Verlag Berlin Heidelberg.

Xu D.,Jiangsu University | Xu D.,University of Electronic Science and Technology of China | Song Q.,Jiangsu University | Zhang K.,Jiangsu University | And 3 more authors.
Wuji Cailiao Xuebao/Journal of Inorganic Materials | Year: 2013

Pure CaCu3Ti4O12 (CCTO) thin film and NiO-doped CaCu3-xNixTi4O12 (CCNTO) thin film with x=0.10, 0.20 and 0.30 were prepared by Sol-Gel method. The effects of NiO on the dielectric properties and microstructure revolution of CCTO were studied. The crystalline structure and the surface morphology of the films were markedly influenced by NiO content. AFM images of the CaCu3-xNixTi4O12 samples showed that the grain size of Ni-doped CCTO was smaller than the grain size of CCTO without Ni doping. For the CCNTO thin film(x=0.2), the lowest leakage current was obtained and the minimum value reached 0.564 mA. Meanwhile, the highest threshold voltage and nonlinear coefficient were 81 V/mm and 1.9, respectively. The dielectric constant increased when the doping content of Ni reached a certain level. Besides, the dielectric loss was decreased firstly, and then increased.

Xu D.,Jiangsu University | Xu D.,University of Electronic Science and Technology of China | He K.,Jiangsu University | Yu R.,Changzhou Ming Errui Ceramics Co. | And 6 more authors.
Journal of Alloys and Compounds | Year: 2014

Pure and alkaline-earth metal titante AETiO3 (AE = Mg, Ca, Sr)-doped CCTO ceramics were prepared by the sol-gel process, and their crystalline structure, microstructural and electrical properties were investigated. The similar doping effects with the existence form of metal titante in CCTO, decreasing the grain size and raising the threshold voltage can be observed in CaTiO3-doped and SrTiO3-doped CCTO ceramics. For MgTiO3-doped CCTO, its grain size increases with the doping amount increasing, the reason can be attributed to the substitution of Mg2+ for Cu2+ in CCTO lattice to increase the liquid Cu-rich phase during sintering processes. In line with IBLC model, the much higher dielectric constant was observed in MgTiO3-doped CCTO ceramics due to their larger grain size. All the samples show a strong nonlinear relationship between electric filed (E) and current density (J). The best-reported dielectric loss value of CCTO ceramic of 0.0243 was obtained in the x = 0.1CaTiO3-doped sample at 104 Hz. © 2014 Elsevier B.V. All rights reserved.

Xu D.,Jiangsu University | Xu D.,University of Electronic Science and Technology of China | He K.,Jiangsu University | Yu R.,Changzhou Ming Errui Ceramics Co. | And 5 more authors.
Materials Chemistry and Physics | Year: 2015

Zn-doped CaCu3-xZnxTi4O12 high dielectric films with low dielectric loss were prepared by the sol-gel method; their crystalline structure, microstructure and electrical properties were investigated. A new method, XRD complemented by CLSM, was used to prove the presence of ZnO in CCZTO films, indicating the existence of the Cu2+ vacancy which influenced the electrical properties directly. The average grain size enlarged with the increased Zn doping amounts. All the samples showed strong non-ohmic properties. Higher nonlinear coefficient and lower leakage current depended on the increased VCu″ concentration. It is significant that the Zn doping effectively reduced the dielectric loss in the low and medium frequency region even though the Zn doping led to the dielectric constant decreased compared to the pure CCTO film. At x = 0.20, the minimum dielectric loss of 0.015 can be observed around 22 000 Hz, which is the best-reported value in CCTO-based material. © 2015 Elsevier B.V. All rights reserved.

Xu D.,Jiangsu University | Xu D.,CAS Institute of Semiconductors | Xu D.,Xian Jiaotong University | Xu D.,University of Electronic Science and Technology of China | And 9 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Y 2O 3-doped ZnO-Bi 2O 3 thin films were fabricated on silicon substrates by sol-gel process and annealed in air at 750 °C for 1 h. Microstructure and electrical properties of ZnO thin films were investigated. XRD analysis shows that all peaks of ZnO thin films are well matched with hexagonal wurtzite structure of ZnO. SEM results present that the ZnO grain size decreases with the increase of dopant concentration, which means that rare earth doped can refine the grain size. The thickness of each layer is uniform and the value of thickness is about 80 nm. The nonlinear V-I characteristics with the leakage current of 0.46 μA, the threshold field of 110 V/mm and the nonlinear coefficient of 3.1 could be achieved when the films contain 0.2 (mole fraction) yttrium ion. © 2012 The Nonferrous Metals Society of China.

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