Entity

Time filter

Source Type


Wan S.,State Grid Electric Power Research Institute of China | Lu W.,Huazhong University of Science and Technology | Fu Z.,Fenghua Advanced Technology Holding Co.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2012

Effect of low-temperature co-firing preparation on the microstructure and electrical properties of ZnO chip varistor prepared using an aqueous tape casting was investigated by environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDXS). The ESEM results show that ZnO varistor sheets and Ag pastes contact with each other compactly under an isostatic pressures of 60 MPa. Ag electrode was distributed continuously and not delaminated with ZnO varistor sheets when co-fired at 900°C. The EDXS and XRD results reveal that Ag electrode remains the state of single matter in ZnO chip varistor when sintered at 900°C. There was no chemical reaction and interfacial diffusion occurred between Ag electrode and ZnO varistor sheets at the interface of ZnO chip varistor. ZnO varistor sheets by aqueous tape casting could be co-fired with Ag electrode at 900°C. The excellent electrical properties of ZnO chip varistor were obtained as follows: Breakdown voltage V 1mA=6.1 V, nonlinear coefficient α=28.1, and leakage current I L=0.15 μA. Source


Huang B.,Nanjing University of Technology | Wang Z.,Nanjing University of Technology | Chen T.,Nanjing University of Technology | Wang L.,Nanjing University of Technology | And 2 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

MnO2 doped Ba4.2Nd9.2Ti18O54–NdAlO3(13 wt%) (BNT–NA) microwave dielectric ceramics with the near zero τf and the wide range of sintering temperature were prepared by conventional solid state method. The effects of Mn4+ doping on the microstructures and microwave dielectric properties of BNT–NA ceramics were investigated. XRD patterns showed only a single BaNd2Ti5O14 phase was identified in all samples and there was no second phase. The sintering temperature decreased from 1,380 to 1,320 °C as MnO2 content increased from 0.1 to 0.9 wt%. The MnO2 doped BNT–NA ceramics could be densified at a lower sintering temperature. The MnO2 additive had a positive effect on lowing sintering temperature of BNT–NA ceramics. The τf varied from negative to positive with the increase of MnO2. Excellent microwave dielectric properties were achieved in Ba4.2Nd9.2Ti18O54–NdAlO3 ceramics doped with 0.3 wt% MnO2 and sintered at 1,380 °C for 2 h: εr = 66.5, Q × f = 13,948 GHz, τf = 0.4 ppm/°C. © 2014, Springer Science+Business Media New York. Source


Huang B.,Nanjing University of Technology | Wang Z.,Nanjing University of Technology | Chen T.,Nanjing University of Technology | Wang L.,Nanjing University of Technology | And 2 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2015

Ba4.2Nd9.2Ti18−xSnxO54(x = 0, 0.25, 0.5, 1, 1.5, 2) microwave dielectric ceramics with high Q × f value were prepared by conventional solid state route. The microstructure and microwave dielectric properties of Ba4.2Nd9.2Ti18−xSnxO54(x = 0, 0.25, 0.5, 1, 1.5, 2)(BNTS) ceramics were systematically investigated. XRD patterns showed that there was only a single BaNd2Ti5O14 phase identified in all samples and no second phase was found. SnO2 substitution increases the lattice parameters of BNT ceramic. Moreover, the bulk density of BNT ceramics increases as the x increases. Both the permittivity and τf value decrease when the Sn concentration increases. The SnO2 substitution has a big influence on Q × f value. When x = 0.5, the BNTS ceramic gains the highest Q × f value. Afterwards, the Q × f value decreases sharply when x value increases. Excellent microwave dielectric properties were achieved in Ba4.2Nd9.2Ti18−xSnxO54(x = 0.5) ceramics sintered at 1340 °C for 2 h: εr = 80.6, Q × f = 9177 GHz, τf = 61 ppm/°C. © 2015, Springer Science+Business Media New York. Source


Huang B.,Nanjing University of Technology | Lu X.,Nanjing University of Technology | Zhang Y.,Nanjing University of Technology | Wang L.,Nanjing University of Technology | And 3 more authors.
Materials Characterization | Year: 2016

Ba4.2Nd9.2Ti18O54 (BNT) ceramics have been prepared by solid-state ceramic method. Dark holes were observed in the center of the ceramics. All the samples showed typical columnar grain morphology in SEM images. TEM and XRD analysis indicated that there was only a BaNd2Ti4O12 (JCPDS Card No. 44-0061) phase in the ceramics. In HRTEM images, the grain boundary was clear and no impurities and defects were observed. The XPS results showed the difference in valence of Ti. Ti3 + ions appeared in all the samples. The Q × f value significantly dropped when the amount of Ti3 + ions was considerable. BNT ceramics sintered at high temperature (1300°C to 1400°C) usually contain dark holes in the center (caused by Ti3 + ions) which could lead to a significant drop in Q × f value. © 2015 Elsevier Inc. All rights reserved. Source


Huang B.,Nanjing University of Technology | Huang B.,Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites | Yan Z.,Nanjing University of Technology | Lu X.,Nanjing University of Technology | And 3 more authors.
Ceramics International | Year: 2016

Large size Ba4.2Nd9.2Ti18O54 (BNT) ceramics doped with MnCO3, CuO and CoO were prepared by the conventional solid-state method. Only a single BaNd2Ti4O12 phase was formed in all samples. No second phase was found in the XRD patterns. The bulk density increases slightly because of the dopants. The SEM results showed that the grain size of Mn2+and Cu2+-doped BNT ceramics became larger with the increasing amount of dopants. The permittivity of all samples stays the same. However, the Q×f value of BNT ceramics increases by doping, especially with Mn2+ ions. The conductivity of BNT ceramic doped with Mn2+(0.5mol‰) under high temperature is lower than that without doping. There are fewer defects in Mn2+-doped BNT ceramics. The XPS results indicated that Ti reduction was suppressed in BNT ceramics doped with 0.5mol‰ Mn2+. BNT ceramics doped with 0.5mol‰ Mn2+ ions sintered at 1320°C for 2h exhibited good microwave dielectric properties, with εr=88.67, Q×f=7408GHz and τf = 82.98 ppm/°C. © 2016 Elsevier Ltd and Techna Group S.r.l. Source

Discover hidden collaborations