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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Low-Temperature Firing and Microwave Dielectric Properties of Zn_3Nb_2O_8 Ceramics with CuO-V_2O_5-Bi_2O_3

    Lin XupingMa JingtaoZhang BaoqingZhou Ji...
    224-227页
    查看更多>>摘要：The influence of CuO-V_2O_5-Bi_2O_3 addition on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Zn_3Nb_2O_8 ceramics were investigated. The co-doping of CuO, V_2O_5 and Bi_2O_3 can significantly lower the sintering temperature of Zn_3Mb_2O_8 ceramics from 1150℃ to 900℃. The Zn_3Nb_2O_8-0.5wt% CuO-0.5wt% V_2O_5-2.0wt% Bi_2O_3 ceramic sintered at 900℃ showed a relative density of 97.1%, a dielectric constant (ε_r) of 18.2, and a quality factor (Q×f) of 36781 GHz. The dielectric properties in this system exhibited a significant dependence on the relative density, content of additives and sintering temperature. The relative density and dielectric constant (ε_r) of Zn_3Nb_2O_8 ceramics increased with increasing CuO-V_2O_5-Bi_2O_3 additions. And also the relative density and dielectric constant of Zn_3Nb_2O_8 ceramics increased by the augment of the sintering temperature.
      原文链接:
    • NETL
    • NSTL

    Microstructure and Leakage Current Characteristics of ZrTiO_4 Thin Films by Sol-Gel Method

    Cheng-Hsing HsuShih-Yao LinHsin-Han Tung
    228-230页
    查看更多>>摘要：This paper describes microstructure and leakage current characteristics of ZrTiO_4 thin films on ITO/Glass substrate were deposited by sol-gel method with a fix per-heating temperature of 250℃ for 30min at various annealing temperatures from 600℃ to 800℃ for 1 hr. The annealed films were characterized using X-ray diffraction. The surface morphologies of annealed film were examined by atomic force microscopy. The dependence of the microstructure and leakage current characteristics on annealing temperature was also investigated.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Preparation and Microwave-Absorption Property of SiO_2-SiC-Based Composites

    Li GuanBingbing FanMingliang LiHejing Wen...
    231-234页
    查看更多>>摘要：SiO_2-SiC composite particles were prepared using a sol-gel process. BaTiO_3 powders were synthesize through solid-state reaction. They were mixed as microwave absorbents with Fe_3O_4 powders to obtain the complex absorption. Epoxide resin (EP) was used as matrix and solidified with the mixtures. The techniques of DSC-TG, XRD were used to characterize the composite particles and the obtained compacts. A vector network analyzer was used to measure the reflectivity of the SiO_2-SiC-based composites. The effects of the aborbents' contents on the reflection of the microwave absorption materials were disscussed. It was found that SiO_2-SiC composites could be prepared using sol-gel process and BaTiO_3 powders could be synthesize through solid-state reaction. The results indicated that SiO_2-SiC composite is contribute to absorb microwave, where SiO_2-SiC: BaTiO_3: Fe_3O_4 = 6:2:2 (vol %), the frequency region in which the maximum reflectivity is more than -10 dB is 5.4-7.6 GHz.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Microstructures and Microwave Properties of CaTiO_3 Doped (ZnMg)TiO_3 Dielectrics with CaO-B_2O_3-SiO_2 Addition

    Bo LiXiaohua ZhouShuren ZhangLongcheng Xiang...
    235-239页
    查看更多>>摘要：The microwave properties and microstructures of (ZnMg)TiO_3-based dielectric prepared by conventional solid-state method were investigated as functions of CaTiO_3 and CaO-B_2O_3-SiO_2 additions. The effects of CaTiO_3 on the crystal phase and the evolution of microstructure of (Zn_(0.65)Mg_(0.35))TiO_3 were studied. The result indicated that CaTiO_3 secondary phase coexists with (ZnMg)TiO_3 main phase in the ZMT-CT ceramics, which confirmed by EDS analysis. Because of CaTiO_3 with large τ_f- value (τ_f = 800 ppm/℃), the temperature coefficient of resonant frequency (τ_f) of ZMT-CT with biphasic structure was adjusted to near zero value. The microwave properties of (Zn_(0.65)Mg_(0.35))TiO_3 ceramics doped with 5wt% CaTiO_3 sintered at 1150℃ were ε ≈ 24, τ_f≈ ±10 ppm/℃, Q×f> 45,000 GHz. Further, it was found that the CaO-B_2O_3-SiO_2 additive could successfully reduce the sintering temperature of (Zn_(0.65)Mg_(0.35))TiO_3-CaTiO_3 ceramics from 1150 to 950℃, and significantly improve the densification of this system, which were densified below 1000℃. This was due to the formation of liquid phases during the sintering observed by SEM. The (Zn_(0.65)Mg_(0.35))TiO_3-0.05CaTiO_3 dielectrics with 1 wt% CaO-B_2O_3-SiO_2 sintered at 950～1000℃ exhibited the optimum microwave properties:ε ≈= 22, Q×f≈ 20,000 GHz and τ_f ≈ ±10 ppm/℃.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Magnetic Properties of Manganese-Titanium Substituted Barium Ferrite Ba(TiMn)_xFe_(12-2x)O_(19)(x=0.0, 0.5,1.0,1.5, 2.0) Prepared by the Molten Salt Method

    Li HaifengGong RongzhouLuo HaoZhou Jun...
    240-243页
    查看更多>>摘要：M-type hexaferrites Ba(TiMn)_x Fe_(12-2x)O_(19) (x=0 to 2) powders were synthesized by molten salt method. X-ray diffraction, scanning electron microscope and vibrating sample magnetometer were used to analyze the structures and electromagnetic properties. The results showed that, the magnetoplumbite structures for all samples were formed. Magnetic hysteresis loop measurements of the Ba(TiMn)_xFe_(12-2x)O_(19), exhibitted that the saturation magnetization (M_s), the remanent magnetization (M_r) and the coercitivity (H_c) of compounds depended strongly on the chemical composition of materials. The maxium values of M_s (52.68emu/g) and M_r (32.89emu/g) of the compounds were found at x=0.5; however, the values of H_c and the areas of magnetic hysteresis loop of compounds decreased with increasing the value of c. The Ba(TiMn)_(1.5)Fe_9O_(19)/paraffin wax composites containing 40vol% of doped barium ferrite exhibitted good absorption performances in the frequency range of 2-14 GHz.
      原文链接:
    • NETL
    • NSTL

    Characterization of Microwave Ceramics with Low Permittivity and High Quality Factors

    Z.X. XiongM.Y. ZhouH. XueH. Qiu...
    244-246页
    查看更多>>摘要：A new type of porous ceramics, Mg_2SiO_4, for microwave application with low permittivity and high quality factors were prepared via gel-casting processing in this paper. Microstructure of the ceramics was observed and crystal structure of the samples was also identified. Moreover, emphasis was paid on the characterization of the microwave ceramics. Dielectric properties of the ceramics were measured by an automatic system of microwave measurement, resulting in dielectric constant of 3.51 and quality factor of 11,774 for the ceramic sample at frequency about 1 OGHz. Mechanical performance of the samples were also evaluated with maximal bending strength of 140MPa.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Fabrication of Barium Titanate Inverse Opals by Sol-Gel Electrophoretic Deposition Process

    Bo LiJinqing WangRei FujiwaraMokoto Kuwabara...
    247-252页
    查看更多>>摘要：Barium titanate (BTO) inverse opal photonic crystals were fabricated by a process of self-assembly of polystyrene opal template in combination with electrophoretic deposition (EPD) of nanoparticles from BTO suspension. In this process, stable monodispersed suspension of BTO nanoparticles was prepared by dispersing BTO gel into a mixed solvent of 2-methoxyethanol and acethylacetone. Then the BTO nanoparticles were infilled into the interstices of the opal template formed by monodisperse polystyrene microspheres by electrophoretic deposition, and then polystyrene template was removed by calcining the specimen at a final temperature of 500℃. SEM images show that the inverse opals possess face-centered cubic (fcc) structure with center to center distant of the air spheres 310 nm. A photonic bandgap in the visible range is observed from reflection spectra of the sample. Such BTO inverse opals as photonic crystals should be useful in device applications.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Dielectric Properties of CaCu_3Ti_4O_(12) Ceramics

    Jinghan YouXiaoyang GongTongwei LiQingdong Chen...
    253-255页
    查看更多>>摘要：CaCu_3Ti_4O_(12) ceramics were prepared by the traditional solid-state reaction method and the dielectric properties were investigated, the activation energy and relaxation time factor of the samples were calculated. Debye relaxation theory was attempted to analyze the experimental datum, the static and high-frequency dielectric constants were obtained according to Cole-Cole spectra. The temperature dependence of the dielectric constant of CaCu_3Ti_4O_(12) were fitted by computer and the theoretical results nearly agree with experimental results.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Sol-gel Process for the Synthesis of Single-phased BaTi_2O_5 Powder

    Guojun LiQi ZhangRuiming RenHao Lue...
    256-258页
    查看更多>>摘要：The single-phased BaTi_2O_5 (BT_2) powders were synthesized by a sol-gel method by using barium acetate and tetrabutyl titanate as starting materials and ZrO_2 as stabilizing agent. A samll amout of ZrO_2 is effective to prepare BT_2 in a single phase and the second phase of BaTiO_3 (BT) and Ba_6Ti_(17)O_(40) (B_6T_(17)) increases with increasing ZrO_2 content. BT_2 starts to form at about 700℃ and BT_2 in a single phase is obtained at 800 to 1250℃ in air at 0.5 mol% ZrO_2. The synthesized grains at 900 ℃ are nearly spherical in shape and whose sizes are 0.2-0.5 μm.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Develop Single-Phase High Dielectric Constant SiO_2-based Composite Gate Dielectric

    Chao-Chin ChanYin-Fang WeiChien-Chen DiaoYuan-Tai Hsieh...
    259-262页
    查看更多>>摘要：In this study, we hoped to find the single-phase high dielectric FET gate-used ceramic materials, which will be used in the sputtering method and have the dielectric constants higher than those of SiO_2 and Si_3N_4. TiO_2, La_2O_3 and ZrO_2 are mixed with SiO_2 to format the (1-x) TiO_2-x SiO_2, (1-x) ZrO_2-x SiO_2 and (1-x) La_2O_3-x SiO_2 compositions, where x is dependent on the different raw materials. The all compositions are calcined at 1100℃ and sintered at 1400℃~ 1550℃ for 2hrs, and the X-ray patterns are used to find the crystal phases of all sintered ceramics. Because of the existence of single-phase, the sintering and dielectric characteristics of 0.3 La_2O_3-0.7 SiO_2 ceramic are further developed.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd