Guo-hua Chen

Guilin University of Electronic Technology, Ling-ch’uan, Guangxi Zhuangzu Zizhiqu, China

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Publications (29)38.46 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: The Dy2O3-doped ZnO–Bi2O3 based varistor ceramics were prepared by a solid state reaction route, and the microstructure and electrical properties were also investigated. The results show that a multiphase composition exists in all samples. With increasing content of Dy2O3, the average size of ZnO grains decreases and the threshold voltage greatly increases. The nonlinear coefficient of the ceramics is in the range of 4.7–60.2, the threshold voltage is in the range of 364.6–884 V/mm, and the leakage current is between 1.77 μA/cm2 and 159.1 μA/cm2. Typically, the varistor ceramics with 0.60 mol.% Dy2O3 sintered at 1050 °C exhibit excellent electrical properties with the threshold voltage of 872.5 V/mm, the nonlinear coefficient of 60.2 and the leakage current of 5.46 μA/cm2. The results show doping Dy2O3 is a promising route for the production of the higher threshold voltage of ZnO–Bi2O3 based varistor ceramics.
    Materials Research Bulletin. 01/2014; 50:141–147.
  • Guo-hua Chen, Ji-le Li, Chang-lai Yuan, Yun Yang
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    ABSTRACT: ZnO-based varistor ceramics with various amounts of CaSiO3 have been prepared by the conventional solid-state reaction route, and the phase composition, microstructure and electrical properties have been investigated by XRD, SEM, a V–I source/measure unit and impedance spectroscopy (IS). The XRD analyses show the presence of primary phase ZnO and some minor secondary phases. The electrical properties analysis results show that the nonlinear coefficient of the varistor ceramics is in the range of 14.9–30.9, the breakdown voltage in the range of 57.0–168.8 V/mm, and the leakage current in the range of 1.1–31.5 μA/cm2. A schematic model for the electrical microstructure of ZnO-based varistor ceramics is proposed with an equivalent circuit of R a (R g C g )(R gbC gb) by IS.
    Journal of Materials Science 01/2014; 49(2). · 2.16 Impact Factor
  • Jun Song, Guo-hua Chen, Chang-lai Yuan, Yun Yang
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    ABSTRACT: Strontium barium niobate-based borate system ferroelectric glass–ceramics with various Sr/Ba ratios were prepared via controlled crystallization method, and the subsequent microstructure, phase evolution, and electrical properties were investigated. The results reveal that increasing Sr/Ba ratio facilitates the formation of uniform dense and fine-grained structure in glass–ceramics and suppresses the crystallization of SBN ferroelectric crystal. The changes in the Sr/Ba ratio dramatically modify the dielectric properties: a high Sr/Ba ratio leads to raised breakdown strength and decreased dielectric constant.
    Materials Letters. 01/2014; 117:7–9.
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    ABSTRACT: Glass-ceramic materials of strontium barium niobate system were prepared through a melt-quenching method. The effects of crystallization temperature on the microstructure, dielectric property, breakdown strength and energy storage density of barium strontium niobate glass-ceramics were studied. The crystallization mechanism of the glass-ceramics was discussed and should be one-dimensional interfacial growth. The results indicate that the breakdown strength remarkably increases with the increase of crystallization temperature. The glass-ceramic heat treated at 900 °C was found to possess optimal properties with breakdown strength of 1300 kV/cm and energy storage density of 2.8 J/cm3, which is promising dielectric materials for high energy storage density dielectrics.
    Transactions of Nonferrous Metals Society of China 01/2014; 24(3):729–735. · 0.92 Impact Factor
  • Journal of Non-Crystalline Solids 10/2013; · 1.60 Impact Factor
  • Guo-hua Chen, Hua-rui Xu, Chang-lai Yuan
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    ABSTRACT: Li2Ti1−x(Zn1/3Nb2/3)xO3 (0≤x≤0.5) ceramics were prepared by a solid state ceramic route, and the phase purity, microstructure, and microwave dielectric properties were investigated. The XRD results suggest the formation of solid solutions for all studied compositions (0≤x≤5). The dielectric properties are strongly dependent on the compositions, the densifications and the microstructures of the samples. The Q×f value increases with x up to x=0.2 and then decreases with the further increase of x. The best microwave dielectric properties of εr=20.5, Q×f =75,257 GHz, and τf =15.4 ppm/°C could be obtained when x=0.2.
    Ceramics International. 07/2013; 39(5):4887–4892.
  • Li Ji-le, Guo-hua Chen, Chang-lai Yuan
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    ABSTRACT: ZnO-based varistor ceramics doped with Nd2O3 and Y2O3 have been prepared by the conventional ceramics method. The phase composition, microstructure and electrical properties of the ceramics have been investigated by XRD, SEM and a V–I source/measure unit. The XRD and EDS analyses show the presence of ZnO, Bi2O3, Zn7Sb2O12, Y2O3, Nd-rich phase and Y-containing Bi-rich phase. The electrical properties analyzed show that the nonlinear coefficient of the varistor ceramics is in the range of 4.4–70.2, the threshold voltage is in the range of 247.1–1288.8 V/mm, and the leakage current is in the range of 1.51–214.6 μA/cm2. The 0.25 mol% Nd2O3 added varistor ceramics with 0.10 mol%Y2O3 sintered at 1050 °C exhibits excellent electrical properties with the high threshold voltage of 556.4 V/mm, the nonlinear coefficient of 61 and the leakage current of 1.55 μA/cm2. The results illustrate that doping Nd2O3 and Y2O3 in ZnO-based varistor ceramics may be a very promising route for the production of the higher threshold voltage and the nonlinear coefficient of ZnO-based varistor ceramics.
    Ceramics International. 04/2013; 39(3):2231–2237.
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    ABSTRACT: The effects of Li2O-MgO-B2O3 (LMB) glass additive on the sintering characteristics, phase purity, microstructure, and microwave dielectric properties of Li2MgTi3O8 ceramics were investigated. The experimental results demonstrate that the addition of LMB glass effectively lowers the sintering temperature of Li2MgTi3O8 ceramic from 1025 °C to 875 °C and induces no obvious degradation of the microwave dielectric properties. Typically, the 1.5% LMB glass-added Li2MgTi3O8 ceramic sintered at 875 °C for 4 h shows excellent microwave dielectric properties of Q×f=45403 GHz, εr=25.9 and τf≈0 °C−1. The dielectric ceramic exhibits stability against the reaction with the Ag electrode, which indicates that the ceramics could be applied in multilayer microwave devices requiring low firing temperatures.
    Transactions of Nonferrous Metals Society of China 01/2013; 23(11):3318–3323. · 0.92 Impact Factor
  • Journal of Materials Science 03/2012; 47(5):2271-2277. · 2.16 Impact Factor
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    ABSTRACT: Ca4-xMgxLa2Ti5O17ceramics were prepared by a solid state ceramic route for x = 0, 0.5, 1, 2, 3 and 4. The structure and microstructure of the ceramics were investigated using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction results show that the Ca4-x Mgx La2Ti5O17 adopts an orthorhombic crystal structure with no secondary phase observed for x from 0 to 0.5. Secondary phase, MgTiO3 occurs with further increasing doping level (1 ≤ x ≤ 3). When x = 4, mixture phases La0.66TiO2.993, MgTiO3 and a trace of unknown phase coexist. Ca4La2Ti5O17 ceramic exhibits a relative permittivity (εr) ~ 65, quality factor (Q × f) ~13,338 GHz (at ~4.75 GHz), and temperature coefficient of resonant frequency (τf ) ~ 165 ppm/°C. The sintering temperature was distinctly reduced from 1,580 °C for x = 0 to 1,350 °C for x = 4. With increasing Mg content, εr and τf obviously decrease, while Q × f value initially decreases and then increases. The ceramic for x = 2 shows εr ~ 50, Q × f ~ 9,451 and τf ~ 62.5 ppm/°C. By the complete replacement of Ca with Mg, Mg4La2Ti5O17 ceramic sintered at 1,350 °C for 4 h combines a high dielectric permittivity (εr = 31), high quality factor (Q × f ~ 15,021) and near-zero temperature coefficient of resonant frequency (τf ~ 4.0 ppm/°C). The materials are suitable for microwave applications.
    Journal of Materials Science Materials in Electronics 01/2012; 23(3):746-752. · 1.49 Impact Factor
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    ABSTRACT: Na2O–BaO–SrO–Nb2O5–B2O3–SiO2 glass-ceramics were prepared by melt-casting followed by controlled crystallization. X-ray diffraction results show that Ba0.27Sr0.75Nb2O5.78 with tungsten bronze structure formed as the dielectric phases from the glass matrix at 800°C. However, a secondary phase NaSr1.2Ba0.8Nb5O15 occurs when crystallization temperature exceeds 850°C. The glass-ceramics exhibit excellent stability in permittivity values from room temperature to 200°C and low dielectric losses below 0.05. Electrical testing demonstrates that the breakdown strength increases with crystallization temperature. The P–E characteristics at room temperature do not show any clear ferroelectric behavior. The glass-ceramic material heated at 800°C/3h + 950°C/3h shows a breakdown strength of 1400kV/cm and its energy storage density can reach up to 4.0J/cm3, which may be a strong candidate for high energy density storage capacitors for portable or pulsed power applications. KeywordsGlass-ceramics–Strontium barium niobate–Electrical property–Capacitor
    Journal of Electroceramics 01/2011; 27(2):78-82. · 1.14 Impact Factor
  • Guo-hua Chen, Hua-rui Xu, Min-hong Jiang
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    ABSTRACT: Strontium barium niobate, Sr0.5Ba0.5Nb2O6 (SBN50) ceramics doping up to 3 wt% V2O5 were fabricated by solid state reaction route, starting from raw materials (oxides and carbonates) of analytical grade. The phase composition, microstructure and dielectric properties were investigated by X-ray diffraction, scanning electric microscope and impedance analyzer. The results show that the addition of V2O5 improves sintering densification of SBN ceramic samples. The relative density of the samples firstly increases and then slightly decreases with increasing amounts of V2O5 and sintering temperature. With the help of the additive of 1 wt% V2O5, the relative density of the sample sintered at 1,280°C for 3h can reached 97.2%. Only single tetragonal tungsten bronze phase SBN exists in all the doped samples. With increase in V2O5 content, the dielectric constant of SBN ceramics at both room temperature and in the vicinity of the phase transition temperature increases significantly and the Curie temperatures (Tc) obviously shifts to low temperature as well as the dielectric loss remains below 0.06. The diffuseness in the phase transition is found to increase with increase in vanadium doping level. The addition of V2O5 results in an increased grain size associated with rod-like grain growth.
    Journal of Materials Science Materials in Electronics 01/2010; 21(2):168-172. · 1.49 Impact Factor
  • Guo-hua Chen, Bing Qi
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    ABSTRACT: 40CaO–20B2O3–40SiO2 (abbreviate as CBS) glass-doped Sr0.5Ba0.5Nb2O6 (SBN50) ceramics were fabricated by solid-state ceramic route. The effects of CBS glass addition on the firing, the phase formation, the microstructure and dielectric characterization of SBN50 ceramics were investigated. Results show that the density of the samples firstly increase and then slightly decrease with increasing CBS glass content and the highest density achieved has been 97% of the theoretical density for the sample with 2% (mass fraction) CBS glass. The sintering temperature was significantly reduced from 1,350 to 1,100 °C. X-ray diffraction analysis shows the single phase tungsten bronze type structure is preserved up to 2% CBS glass. However, the samples with more than 5% CBS glass are found to have a secondary phase CaNbO3. The diffuse character and the dielectric constant at room temperature increase as CBS glass content increases. The dielectric constant of the samples at the Curie temperature (T c) firstly increases and then decreases with increasing the content of CSB glass. Interestingly, the grain sizes of SBN phase are found to obviously increase with increase in CBS glass doping level.
    Journal of Materials Science Materials in Electronics 01/2009; 20(3):248-252. · 1.49 Impact Factor
  • Guo-hua Chen, Bing Qi
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    ABSTRACT: 16CaO–29Al2O3–34SiO2–13PbO–4B2O3–2ZnO–2P2O5 (CASP) glass doped-Sr0.5Ba0.5Nb2O6 (SBN50) ceramics have been synthesized by solid-state ceramic route. The effects of CASP glass on the firing, microstructure and dielectric characterization of SBN50 ceramics are investigated. The densities of the ceramic samples firstly increase and then slightly decrease with increasing CASP glass content. The appropriate amount of doping glass is 2%. The SBN50 ceramics doped with CASP glass can be sintered at a relatively low temperature, 1200°C. X-ray diffraction analysis shows the single phase (tetragonal tungsten bronze type structure) is preserved for all the samples. The diffuse character of the ceramic system increases and the dielectric constant at phase transition temperature (Tc) markedly decreases as CASP glass content increases. Interestingly, the CASP glass addition drastically alters the microstructure of the sintered ceramics. The isotropic grains in the pure SBN50 ceramics transform to rod like grains after the addition of CASP glass. The grain size of SBN phase is found to obviously increase with increase in CASP glass doping level.
    Journal of Alloys and Compounds 01/2009; 473(1):414-417. · 2.39 Impact Factor
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    ABSTRACT: CBS (CaO–B2O3–SiO2) glass/cordierite (Mg2Al4Si5O18) ceramic composites were prepared using standard ceramic process. Effects of cordierite on crystallization behavior of the CBS glass powder were investigated. Results showed that crystalline phases like pseudowollastonite (CaSiO3) and quartz (SiO2) were formed during the firing of glass alone. For the composites with ≥45 vol. % cordierite at 780–1200 °C, the above crystalline phases were completely prevented but new phase of anorthite (CaAl2Si2O8) was formed. For all the composites, the intensity of peaks characterizing cordierite gradually decreases and that of characterizing anorthite synchronously enhances with increasing sintering temperature. Microstructural changes of all the samples with sintering temperature were in good agreement with the relative density and an optimum firing temperature for maximum densification existed for each glass/ceramic ratio. The thermal expansion coefficient (TEC) of the composites decreases with increase in cordierite ceramic volume percent. The TEC of all the composites was in the range of 2.2 × 10−6 K−1 to 5.2 × 10−6 K−1. The dielectric constant of the fabricated composites was between 5.2 and 6.2. The precipitation of anorthite has no bad effect on the dielectric constant and the TEC of the resulting composites because anorthite has low dielectric constant (6.2) and low thermal expansion coefficient (4.82 × 10−6 K−1). The prepared glass/ceramic composites were well suited for LTCC application.
    Journal of Alloys and Compounds. 01/2009;
  • Guo-hua Chen
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    ABSTRACT: The effects of replacement of MgO by CaO on the sintering, and crystallization behavior of MgO–Al2O3–SiO2 system glass–ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature (Tg) firstly increased, and then decreased. The melting temperature was lowered, and the crystallization temperature of the glass–ceramics shifted clearly towards higher temperatures. With the replacement of MgO by less than 3wt% CaO, the predominant crystalline phase in the glass–ceramics, fired at 900°C, was found to be α-cordierite, and the secondary crystalline phase to be μ-cordierite. When the replacement was increased to 10wt%, the predominant crystalline phase was found to be anorthite, and the secondary phase to be α-cordierite. Both the thermal expansion coefficient (TCE), and the dielectric constant of the samples increase by replacing MgO by CaO. The dielectric loss of the sample with 5wt% CaO (C5), fired at 900°C, has the lowest value of 0.08%. Only the sample C5 and the sample containing 10wt% CaO, (C10), can be fully sintered before 900°C. Therefore, a dense, and low dielectric loss glass–ceramic with predominant crystal phase of α-cordierite, and some amount of anorthite was achieved by using fine glass powders (D50=3μm), fired at 875–900°C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample C5 firstly increases, and then decreases with sintering temperature, which closely corresponds to its relative density. The TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures depends not only on its relative density, but also on its crystalline phases. The dense, and crystallized glass–ceramic C5 exhibits a low sintering temperature (≤900°C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10−3) at 1MHz, a low TCE (4.0–4.25×10−6K−1), very close to that of Si (∼3.5×10−6K−1), and a higher flexural strength (≥134MPa), suggesting that it would be a promising material in the electronic packaging field.
    Journal of Alloys and Compounds 01/2008; 455(1):298-302. · 2.39 Impact Factor
  • Guo-Hua Chen, Xin-Yu Liu
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    ABSTRACT: The effect of replacement of Al2O3 by ZnO on the sintering and crystallization behavior of MgO–Al2O3–SiO2 system glass-ceramics was investigated. The results show that with increasing ZnO content, the melting temperature and crystallization temperature of the glass-ceramics were lowered, and the glass transition temperature firstly decreased and then increased. With the replacement of 5 and 8 wt.%, the predominant crystalline phase in the glass-ceramics was found to be α-cordierite and the secondary crystalline phase to be gahnite and quartz. When the replacement was increased to 11 wt.%, the predominant crystalline phase was found to be gahnite and quartz and the secondary phase to be α-cordierite. Only the sample containing 8 wt.% ZnO (abbreviated as sample Z8) can be fully sintered before 1000 °C. Therefore, a dense and low dielectric loss glass-ceramic with predominant crystal phase of α-cordierite and gahnite is achieved by using fine glass powders (D50 = 3 μm) fired at 900–925 °C. The as-sintered density approaches 97.0% theoretical density. The flexural strength of sample Z8 increases with sintering temperature, which closely corresponds to its relative density. The thermal expansion coefficient (TCE) of sample Z8 sintered at different temperatures mainly depends on its crystalline phases. The dielectric property of sample Z8 sintered at different temperatures depends on not only its relative density but also its crystalline phases. The dense and crystallized glass-ceramic Z8 exhibits a fairly low dielectric constant (5.0–5.2), a low dielectric loss (≤10−3) at 1 MHz, a low thermal expansion coefficient (4.0–4.2 × 10−6 °C−1), very close to that of Si (∼3.5 × 10−6 °C−1) and a higher flexural strength ≥125 MPa), suggesting that it would be a promising material in the electronic packaging field.
    Journal of Alloys and Compounds 01/2007; 431:282-286. · 2.39 Impact Factor
  • Guo-hua Chen
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    ABSTRACT: The influences of addition of ZnO on sintering, crystallization behavior and properties of cordierite-based glass-ceramics were investigated. Results show that with increasing ZnO content, the batch melting temperature, glass transition temperature and crystallization temperature all decrease. Addition of ZnO can greatly improve the sinterability of the glass powders and alter the type of the crystalline phases. Addition of 1.5wt% ZnO seems to be reasonable. Thermal expansion coefficients (TCEs) of samples increase with increasing ZnO contents. The density was found to be an important factor affecting the dielectric loss of the samples. Dielectric constant and TCEs of the sintered bulk samples were found to depend on their relative densities and crystalline phases. The samples doped with 1.5–3.0wt% ZnO sintered at 950°C has a low dielectric constant (5.0–5.2), a low dielectric loss (≤0.0018) and a low thermal expansion coefficient (3.6–4.8×10−6K−1), which are promising electronic packaging materials.
    Journal of Materials Science Materials in Electronics 01/2007; 18(12):1253-1257. · 1.49 Impact Factor
  • Guo-Hua Chen
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    ABSTRACT: The effects of replacement of MgO by CaO on the sintering and crystallization behavior of MgO–Al2O3–SiO2 system glass-ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature firstly increased and then decreased, the melting temperature was lowered and the crystallization temperature of the glass-ceramics shifted clearly towards higher temperatures. With the replacement of MgO by less than 3 wt.% CaO, the predominant crystalline phase in the glass-ceramics fired at 900 �C was found to be α-cordierite and the secondary crystalline phase to be μ-cordierite. When the replacement was increased to 10 wt.%, the predominant crystalline phase was found to be anorthite and the secondary phase to be α-cordierite. Both thermal expansion coefficient (TCE) and dielectric constant of samples increases with the replacement of MgO by CaO. The dielectric loss of sample with 5 wt.% CaO fired at 900 �C has the lowest value of 0.08%. Only the sample containing 5 wt.% and10 wt.% CaO (abbreviated as sample C5 and C10) can be fully sintered before 900 �C. Therefore, a dense and low dielectric loss glass-ceramic with predominant crystal phase of α-cordierite and some amount of anorthite was achieved by using fine glass powders (D50 = 3 μm) fired at 875–900 �C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample C5 firstly increases and then decreases with sintering temperature, which closely corresponds to its relative density. The TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures depends on not only its relative density but also its crystalline phases. The dense and crystallized glass-ceramic C5 exhibits a low sintering temperature (≤900 �C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10−3) at 1 MHz, a low TCE (4.0–4.25 � 10−6 K−1), very close to that of Si (∼3.5 � 10−6 K−1), and a higher flexural strength (≥134 MPa), suggesting that it would be a promising material in the electronic packaging field.
    Journal of Materials Science 01/2007; 42(17):7239-7244. · 2.16 Impact Factor
  • Guo-hua Chen, Xin-yu Liu
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    ABSTRACT: To meet the demands of high power and high-speed propagation of the signal for very large scale integration, a series of glass/ceramic composites were prepared using electronic ceramics process from borosilicate glass with Sr-celsian, which contains 30, 40, 50, 60, 70 wt% ceramic. The phase and microstructural evolution of the composites were characterized by XRD and SEM. The properties of the composites were also measured. Results show that the thermal expansion coefficient, dielectric constant and hardness of the composites increase with an increase content of Sr-celsian. However, the dielectric loss decreases with increasing Sr-celsian content. For the composites with ≧ 60 wt% Sr-celsian fired at 850–900°C, formation of α-quartz and cristobalite in the composites during the sintering process has bad effect on thermal expansion, but has little effect on the values of dielectric properties of the composites. The obtained composites exhibit low dielectric constant (5.2–5.8), low dielectric loss (⩽ 0.25%), low thermal expansion coefficient (4.4–6.2× 10−6°C−1) and low-temperature sintering behavior (⩽900°C), which suit for electronic packaging field.
    Journal of Materials Science Materials in Electronics 10/2006; 17(11):877-882. · 1.49 Impact Factor