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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.,University of Electronic Science and Technology of China | He K.,Jiangsu University | He K.,University of Electronic Science and Technology of China | And 8 more authors.
Materials Technology | Year: 2015

Pr2O3 and Pr6O11 doped ZnO thin films were prepared by the sol-gel method respectively. The microstructure and electrical characteristics of the samples were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), varistor dc parameter analyser and impedance analyser. Two kinds of Pr-oxide doped ZnO thin film with similar phase which contain well crystallised ZnO. The grains of Pr2O3 doped ZnO thin films and Pr6O11 doped ZnO thin films are uniform and closely packed, and all samples have lower surface roughness. When the doping content of Pr2O3 is 0·90 mol.-%, the varistor properties of ZnO thin film are optimum, the leakage current is 487 mA, the potential gradient is 232 V mm-1 and the nonlinear coefficient is 2·5. The dielectric constant of ZnO thin films increases in a certain degree with different contents of Pr2O3 and Pr6O11 doping. The Pr2O3 doping reduces the dielectric loss effectively, but the Pr6O11 doping has the opposite effect. These results provide favourable theoretical and experimental basis to optimise and extend electrical application of ZnO thin film. © 2015 W. S. Maney & Son Ltd.


Zhang C.-H.,Jiangsu University | Zhang C.-H.,CAS Institute of Semiconductors | Zhang C.-H.,Xi'an Jiaotong University | Zhang C.-H.,University of Electronic Science and Technology of China | And 12 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Dielectric properties and varistor performance of sol-gel prepared Ni-doped calcium copper titanate ceramics (CaCu 3Ni xTi 4O 12+x, x=0, 0.1, 0.2, 0.3) were investigated. SEM and XRD were used in the microstructural studies of the specimens and the electrical properties were investigated for varistors. XRD patterns show that the CCTO ceramics were single phase with no Cu-rich phase. SEM results indicated that the samples had smaller grain sizes than those synthesized by traditional solid-state reaction methods. The experimental results show that the highest dielectric constant and lower dielectric loss occur when x=0.2. When x=0.3, the lowest leakage current is obtained and the maximum value reaches 0.295; meanwhile, the lowest threshold voltage and nonlinear coefficient are found, the minimum values of them are 1326 V/mm and 3.1, respectively. © 2012 The Nonferrous Metals Society of China.


Xu D.,Jiangsu University | Xu D.,CAS Institute of Semiconductors | Xu D.,Xi'an 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.


Xu D.,Jiangsu University | Xu D.,CAS Institute of Semiconductors | Xu D.,Xi'an Jiaotong University | Xu D.,University of Electronic Science and Technology of China | And 8 more authors.
Journal of Rare Earths | Year: 2013

A series of ZnO-Bi2O3-based varistor ceramics doped with 0-0.4 mol.% Sc2O3 were prepared by high-energy ball milling and sintered at temperatures between 1000 and 1150°C. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to characterize the phases and microstructure of the varistor ceramics. A DC parameter instrument for varistor ceramics was applied to investigate the electronic properties and V-I characteristics. The results showed that there were no changes in crystal structure with Sc2O3-doped varistor ceramics and that the average size of ZnO grain increased first and then decreased. The best electronic characteristics of the varistor ceramics prepared by high-energy ball milling were found in 0.3 mol.% Sc 2O3-doped ZnO-Bi2O3-based ceramics sintered at 1000°C, which exhibited a threshold voltage of 821 V/mm, nonlinear coefficient of 62.1 and leakage current of 0.16 μA. © 2013 The Chinese Society of Rare Earths.


He K.,Jiangsu University | Wu W.,Jiangsu University | Chen B.,Changzhou Ming Errui Ceramics Co. | Wu J.,Jiangsu University | And 3 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2015

A kind of rare earth metal cerium doped ZnO-Bi2O3 varistor thin films were prepared by the sol-gel method. The XRD, AFM, dielectric properties and varistor characteristics were investigated. According the results, the crystal structure of ZnO-Bi2O3 varistor thin films couldn't be influenced by Ce doping, while the grain size were decresed. The leakage current and dielectric loss could be decreased by Ce doping, and the nonlinear characteristics could be improved. The threshold voltage of ZnO-Bi2O3 varistor thin film was increased to 175 V/mm and the leakage current was declined to 502 μA through 0.3mol% Ce doping. © 2015, Journal of Functional Materials. All right reserved.


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.,Changzhou Ming Errui Ceramics Co. | He K.,Jiangsu University | Jiao L.,Jiangsu University | And 5 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2016

The microstructure and electrical properties of ZnO varistor ceramics with different ZrO2 content prepared by a solid reaction route and sintered at 1100 °C were investigated. The microstructures of the varistor ceramics samples were characterized by X-ray diffraction and scanning electron microscopy; the electrical properties and current–voltage (V–I) characteristics of the varistor ceramics were investigated by DC parameter instrument. The microstructure of the prepared samples shows a decrease in grain size of ZnO phase with the ZrO2 content increase. ZrO2-doped ZnO varistor ceramics exhibit comparatively vastly superior comprehensive electrical properties with addition of 0.50 mol% ZrO2, such as the threshold voltage is 350 V/mm, the nonlinear coefficient is 25.4 and the leakage current is 2.96 μA. © 2015, Springer Science+Business Media New York.

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