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Dong W.,Australian National University | Hu W.,Australian National University | Frankcombe T.J.,Australian National University | Frankcombe T.J.,University of New South Wales | And 9 more authors.
Journal of Materials Chemistry A | Year: 2017

Colossal permittivity (CP) materials have many important applications in electronics but their development has generally been hindered due to the difficulty in achieving a relatively low dielectric loss. In this work, we report an In + Ta co-doped TiO2 material system that manifests high dielectric permittivity and low dielectric loss based on the electron-pinned defect-dipole design. The dielectric loss can be reduced down to e.g. 0.002 at 1 kHz, giving high performance, low temperature dependent dielectric properties i.e. εr > 104 with tan δ < 0.02 in a broad temperature range of 50-400 K. Density functional theory calculations coupled with the defect analysis uncover that electron-pinned defect dipoles (EPDDs), in the form of highly stable triangle-diamond and/or triangle-linear dopant defect clusters with well-defined relative positions for Ti reduction, are also present in the host material for the CP observed. Such a high-performance dielectric material would thus help for practical applications and points to further discovery of promising new materials of this type. © The Royal Society of Chemistry.


Geng S.,Fenghua Advanced Technology Holding Co. | Wan M.,Fenghua Advanced Technology Holding Co. | Huang K.,Fenghua Advanced Technology Holding Co.
Yadian Yu Shengguang/Piezoelectrics and Acoustooptics | Year: 2014

The simulation and design of SAW low loss ladder filter with 42°Y-X LiTaO3 substrate have been carried out by using COM and P matrix cascading technology. By analyzing the impact of SiO2 layer thickness on the center frequency deviation of filter and establishing the equivalent circuit model to simulate the package, a 4-order SAW ladder filter with the out-of-band rejection of more than 20 dB and the insertion loss of less than -1.2 dB at the center frequency of 1575 MHz has been designed. The simulation result and measurement result agree well.


Xu Y.,Nanjing University of Aeronautics and Astronautics | Fu R.,Nanjing University of Aeronautics and Astronautics | Li J.,Nanjing University of Aeronautics and Astronautics | Fu Z.,Fenghua Advanced Technology Holding Co. | Su H.,Fenghua Advanced Technology Holding Co.
Key Engineering Materials | Year: 2014

The effect of LnAlO3 (Ln = Nd, Sm) additives on the densification, phase evolution, microstructure and dielectric properties of BaO-Nd2O3-5TiO2(BNT5) ceramics was investigated. The LnAlO3 (Ln = Nd, Sm) had greatly influence on the densification behavior of the BNT5 ceramics and the grain sizes of BNT5 ceramics could be effectively refined by LnAlO3 additive. The microstructure of BNT5 ceramics was transformed from quasi-rectangular grain to columnar grain while the content of LnAlO3 was increasing. The dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) were reduced with the increase of LnAlO3 content, whereas the Qxf values showed a non-linear behaviour with LnAlO3 content increasing. The BNT5 ceramics doped with 12.5 wt% SmAlO3, sintered at 1320°C for 4 h, had the excellent dielectric properties of εr = 62.78, Qxf = 11108 GHz and τf = -1.55 ppm/°. © (2015) Trans Tech Publications, Switzerland.


Chen T.,Nanjing University | Wang Z.-F.,Nanjing University | Huang B.-Y.,Nanjing University | Wang L.-X.,Nanjing University | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2015

0.9Al2O3-0.1TiO2 ceramics were prepared by reaction sintering method. The effects of annealing time, annealing atmosphere on phase composition, microstructure, microwave dielectric properties were studied. The results show that the second phase Al2TiO5 was decomposed by annealing treatment, with a regular surface and high density. Prolonged annealing time and proper annealing atmosphere could effectively improve the Q×f value of 0.9Al2O3-0.1TiO2 ceramics. Excellent dielectric properties were obtained with εr=12.50, Q×f=79812 GHz, τf =0.13 ppm/℃ when sintered at 1350℃ for 4 h, annealed at 1100℃ for 20 h in O2 atmosphere. ©, 2015, Rengong Jingti Xuebao/Journal of Synthetic Crystals. All right reserved.


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.


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.


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.


Wang Z.-F.,Nanjing University of Technology | Gong Z.-J.,Nanjing University of Technology | Wang L.-X.,Nanjing University of Technology | Fu Z.-X.,Fenghua Advanced Technology Holding Co. | And 2 more authors.
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2012

Ba(Co1/3Nb2/3)O3 microwave dielectric ceramics were prepared by conventional solid-state method. The effects of pre-calcined temperatures on the phase composition, microstructure, sintering property and microwave dielectric property were studied. The results showed that the main crystal phase of the ceramics under the different pre-calcined temperatures was Ba3CoNb2O9 with complex perovskite structure, but small amount of Ba3Nb5O15 appeared when the pre-calcined temperature was 900°C and 1000°C. The optimal microwave dielectric properties were obtained with εr of 31.8, Q×f of 60164 GHz and τf of -15 × 10-6/°C when the pre-calcined temperature was 1100°C and the sintering temperature was 1380°C for 4 h. The optimized pre-calcined temperature prevented the formation of the second phase, which improved the compactness of the material and made the atoms of B site in the main crystal phase be well ordered and further reduced dielectric loss.


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.


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.

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