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Cao Q.-S.,Huazhong University of Science and Technology | Cao Q.-S.,Key Laboratory of Functional Materials for Electronic Information B | Lu W.-Z.,Huazhong University of Science and Technology | Lu W.-Z.,Key Laboratory of Functional Materials for Electronic Information B | And 6 more authors.
Ceramics International | Year: 2015

Low-temperature co-fired ceramics (LTCCs), with a Zn(Mn1-xTix)3O7 (0≤x≤1.0) composition, were prepared using a conventional solid-state method. A novel ZnMn3O7 ceramic was obtained, with a ZnMn2O4 spinel structure, εr of 7.32, Q×f of 13,667 GHz, and τf of -58.33 ppm/°C. The effect of various dopant concentrations on the microstructure and microwave dielectric properties of the material was investigated. Results showed that the increase in dopant concentration changed the phase composition, improved the microwave dielectric properties, and reduced the sintering temperature of the Zn(Mn1-xTix)3O7 by a factor of 250 °C. The dielectric constant of Zn(Mn1-xTix)3O7 varied from 7.32 to 33.08 at x=0.8. However, the maximum value was reduced to 27.67 at x=1.0. Moreover, the value of Q×f increased significantly up to a maximum value of 18,934 GHz, whereas τf changed gradually from -58.33 ppm/°C to +289.25 ppm/°C. In addition, promising LTCC materials with stable temperature characteristics and co-firing compatibility with silver electrodes can be obtained in the nominal Zn(Mn1-xTix)3O7 (x=0.68) ceramics with 5 wt% ZnO-B2O3 glass sintered at 900 °C. This material possesses the following microwave dielectric properties: εr of 18.2, Q×f of 12,018 GHz, and τf of -3.98 ppm/°C. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


Xue J.,South China University of Technology | Wu S.,South China University of Technology | Li J.,Shen Zhen Zhen Hua Ferrite and Ceramic Electronics Co.
Journal of the American Ceramic Society | Year: 2013

Spinel ZnGa2O4 ceramics were synthesized by conventional solid-state method and their microwave dielectric properties were investigated. The phase evolution and microstructures of specimens were studied by XRD and SEM. The textured surface microstructures of ZnGa2O 4 ceramics formed at high sintering temperatures. The spinel-structured ZnGa2O4 ceramics sintered at 1385°C exhibited excellent microwave dielectric properties: a dielectric constant (εr) of 10.4, a quality factor (Q × f) of 94.600 GHz, and a temperature coefficient of resonant frequency (τf) of -27 ppm/°C. ZnGa2O4 ceramics have a low sintering temperature, a wide temperature region, and a small negative τf value. They are promising candidate materials for millimeter-wave devices. © 2013 The American Ceramic Society.


Wu S.,South China University of Technology | Xue J.,South China University of Technology | Wang R.,South China University of Technology | Li J.,Shen Zhen Zhen Hua Ferrite and Ceramic Electronics Co.
Journal of Alloys and Compounds | Year: 2014

Spinel MgGa2O4 ceramic materials were synthesized by solid-state method. MgGa2O4 powders were investigated with X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, Raman spectrum, X-ray photoelectron spectrum (XPS), and high resolution transmission electron microscopy (HRTEM). The spinel-structured MgGa 2O4 ceramics sintered at 1410 C exhibited excellent microwave dielectric properties: a dielectric constant (Ér) of 9.54, a quality factor (Q × f) of 117,000 GHz (at 14.7 GHz frequency) and a temperature coefficient of resonant frequency (τf) of -4.0 ppm/ C. MgGa2O4 ceramics have a wide sintering temperature region (∼150 C) and nearly zero τf value. The large relative density, uniform microstructure and cation ordering resulted in high Q × f values. Crystal distortion from the oriented growth was advantageous to produce nearly zero τf value. MgGa2O4 ceramics are promising candidate materials for millimeter-wave devices. © 2013 Elsevier B.V. All rights reserved.


Wu S.P.,South China University of Technology | Zhao Q.Y.,South China University of Technology | Zheng L.Q.,South China University of Technology | Ding X.H.,Shenzhen Zhenhua Ferrite and Ceramic Electronics Co.
Solid State Sciences | Year: 2011

The ZnO-doped silver paste with good thixotropy was prepared and its cofiring characteristics with ferrite green tapes were studied. The sheet resistivity of silver film decreased with an increasing temperature because of larger grain size and denser film. 2 wt.% ZnO-doped silver thick film showed low sheet resistivity (0.97 m/ (m/mm2)), high adhesive strength (0.85 kgf·mm-2) and excellent compatibility. ZnO scattered at the silver grain boundaries according to SEM photographs. The pinning effect led to a decreased grain size when the amount of ZnO increased. A grain growth exponent n = 3.0-4.58 was evaluated by minimizing the deviation in the function D n - D0 n = k (T) t to the experimental data. The average activation energy (47 kJ/mol) indicated that surface diffusion mass transportation was the mechanism of silver grain growth. © 2011 Elsevier Masson SAS. All rights reserved.


Ma Q.,South China University of Technology | Wu S.,South China University of Technology | Fan Y.,Shen Zhen Zhen Hua Ferrite and Ceramic Electronics Co.
Ceramics International | Year: 2014

Zn2SnO4 ceramics were synthesized by the solid-state method. B2O3 was added into the system to lower the sintering temperature. B2O3-doped Zn2SnO 4 materials were characterized by X-ray diffraction (XRD), electron microscopies (SEM/TEM/HRTEM/EDS), Raman and XPS spectroscopies. The inverse-spinel Zn2SnO4 ceramics (containing 1 wt% B 2O3) sintered at 975 C exhibited good microwave dielectric properties: εr=9.3, Q×f=62,000 GHz and τf=-50 ppm/ C. Zn2SnO4 ceramics with low sintering temperatures are promising candidate materials for low-temperature cofired millimeter-wave devices. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.


Wu S.P.,South China University of Technology | Zheng L.Q.,South China University of Technology | Zhao Q.Y.,South China University of Technology | Ding X.H.,Shenzhen Zhenhua Ferrite and Ceramic Electronics Co.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2010

Conductive silver terminal paste for multilayer chip inductances (MLCIs) was prepared. Surfactant could decrease the apparent viscosity of silver paste and improve the densification of the fired silver films, however, surplus surfactant would worsen the levelability of silver paste because of the decrease in the surface tension of the printed thick films. Suitable dosage of lead-free glass and sintering temperature are also very important to obtain the qualified thick films. Silver thick films containing 5wt.% frit/silver have high adhesion strength (119Kgfcm-2), low sheet resistance (5.4mΩ/□), dense microstructure and excellent electroplating behavior at the fired temperature of 850°C. MLCIs with as-synthesized silver terminal paste have excellently electrical and mechanical properties. © 2010 Elsevier B.V.


Ma Q.,South China University of Technology | Wu S.,South China University of Technology | Jiang C.,South China University of Technology | Li J.,Shen Zhen Zhen Hua Ferrite and Ceramic Electronics Co.
Ceramics International | Year: 2013

SnO2-doped CaSiO3 ceramics were successfully synthesized by a solid-state method. Effects of different SnO2 additions on the sintering behavior, microstructure and dielectric properties of Ca(Sn1-xSix)O3 (x=0.5-1.0) ceramics have been investigated. SnO2 improved the densification process and expanded the sintering temperature range effectively. Moreover, Sn4+ substituting for Si4+ sites leads to the emergence of Ca 3SnSi2O9 phase, which has a positive effect on the dielectric properties of CaO-SiO2-SnO2 materials, especially the Qf value. The Ca(Sn0.1Si0.9)O3 ceramics sintered at 1375 °C possessed good microwave dielectric properties: εr =7.92, Qf =58,000 GHz and τf=-42 ppm/°C. The Ca(Sn0.4Si0.6)O3 ceramics sintered at 1450 °C also exhibited good microwave dielectric properties of εr=9.27, Qf=63,000 GHz, and τf=-52 ppm/°C. Thus, they are promising candidate materials for millimeter-wave devices. © 2012 Elsevier Ltd and Techna Group S.r.l.


Wu S.,South China University of Technology | Xue J.,South China University of Technology | Fan Y.,Shen Zhen Zhen Hua Ferrite and Ceramic Electronics Co.
Journal of the American Ceramic Society | Year: 2014

Spinel Mg(Al1 - xGax)2O4 (x = 0-1) solid solutions were synthesized via solid-state method. Replacement of Al3+ by Ga3+ in MgAl2O4 gave rise to the expansion of the lattice, as well as blueshifts of FT-IR and Raman peaks. The homogeneous solid solutions, high relative densities, large grain sizes, and compact microstructures resulted in excellent microwave dielectric properties for spinel Mg(Al1 - xGax)2O4 (x = 0.6) ceramics sintered at 1485° C: that is, εr = 8.87, Q × f = 107 000 GHz (at 14.8 GHz), and τf = - 16 ppm/°C. Spinel-structured Mg (Al1 - xGax)2O4 (x = 0-1) solid solutions possessed low sintering temperatures, wide temperature regions (∼100 °C), and small negative sf values. These outstanding performance make Mg(Al, Ga)2O4 a promising candidate material for millimeterwave devices. © 2014 The American Ceramic Society.

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