BaAlxFe12—xO19铁氧体的微波特性

用普通陶瓷工艺制备了ＢａＡｌｘＦｅ１２－ｘＯ１９铁氧体,研究了比饱和磁化强度、居里温度、介电损耗和磁晶各向异性同铝含量的关系,并对阳离子的占位情况进行了讨论。     

Thick films for multilayer substrates

Abstract

Low temperature fired ceramics based on alumina/glass added oxide ceramics have been developed and are being used by several companies as substrates for high density assembled modular packaging.^1–3 The features of low temperature fireable substrates are the cofireability with highly conductive metals such as Ag, Ag-Pd, or Cu, and the cofireability with other passive component materials for L, C, R and relatively low dielectric constant elements. But most of these substrates have the disadvantage that their thermal expansion coefficient is not perfectly compatible with Si or GaAs. This paper reports the results of a newly developed cordierite/glass based substrate employing Cu as the surface and internal conductors and having the freedom of tuning the thermal expansion coefficient by changing the composition. The ceramic composition with adjustable thermal expansion coefficient value of 3 to 7 ppm/°C can be manufactured and easily matched with the thermal expansion coefficient of Si or GaAs without a big change of electrical performance.     

Characterization of Hydrothermally Synthesized PLZT for Pyroelectric Applications

PLZT fine powders have been synthesized by a hydrothermal process using lead acetate, lanthanum acetate, zirconium n-propoxide and titanium isopropoxide as starting materials. The synthesis was performed at 200°C for 8, 12 and 24 h. 4 M KOH was used as a mineralizer to adjust the pH to an optimum value for the mixed precursor solution. After hydrothermal treatment the solid portion was separated out, washed and dried at 100°C for 12 h, where PLZT fine powders were obtained. PLZT powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The PLZT powders were pressed and sintered to obtain high density ceramics, which then were investigated by XRD and SEM. The dielectric properties of the ceramics were investigated by measurements of dielectric constant and dielectric loss as a function of temperature at a fixed frequency.     

Co离子添加对NiZn铁氧体电磁性能的影响

用传统的陶瓷工艺制备了Co掺杂Ni0.24Zn0.6Fe1.98O4铁氧体材料,研究了Co掺杂量对NiZn铁氧体磁性能的影响.实验发现,在掺杂少量Co的情况下,随着掺杂量的增加,NiZn铁氧体的晶粒均匀生长,截止频率增高,损耗减小,介电常数在较宽频率范围稳定.因而,添加适量的Co离子,能有效改善NiZn铁氧体的性能.     

Low Loss Tungsten-Based Electrode Technology for Microwave Frequency BST Varactors

The electrical properties of BaO-Nd₂O₃-Sm₂O₃-TiO₂ ceramics doped with low loss glass or low melting point oxide B₂O₃ are evaluated by impedance spectroscopy. Glass or B₂O₃ is doped as liquid phase sintering aid. Doping of glass/B₂O₃ enhances both the growth in the longitudinal direction of the columnar crystal and the preferred orientation of (002). The grain size increases and grain boundary decreases with the increase of dopant. Both the grain and grain-boundary resistivities decrease with the increase of dopant. The grain boundary activation energy for charge transport is larger than that of the grain activation energy. Possible mechanisms for the electrical behavior of the liquid-phase sintered BaO-Nd₂O₃-Sm₂O₃-TiO₂ ceramics are proposed and discussed.     

Sn~(4+)取代对Ni系微波铁氧体材料性能的影响

采用普通陶瓷工艺制备了Sn4+取代的Ni系尖晶石Ni1-a+xCuaSnxMnbFe2-b-2xO4微波多晶铁氧体材料,研究了材料性能随Sn4+取代量的变化。结果表明,铁磁共振线宽ΔH随Sn4+取代量x的增大先减小后增大,当x=0.1时,ΔH有最小值;饱和磁化强度Ms、居里温度TC随取代量x的增大单调降低,在x=0.1时不存在拐点。初步分析了各向异性线宽ΔHa和气孔致宽ΔHp对ΔH的贡献,得出ΔH先降低而后增大是由各向异性线宽ΔHa所致。     

Reactive Calcination Derived PZT Ceramics

Perovskite PZT ceramics are synthesized from stoichiometric oxide ratios of Pb, Zr, and Ti. The oxide powders are mixed mechanically and calcinated, and then sintered to form the desired perovskite phase using conventional solid-state reaction and reactive calcination routes. Highly reactive powders are produced by reacting the materials near the temperature of maximum volumetric expansion. At this point, an almost single phase with relatively high homogeneous structure is obtained. Also, the highly reactive powders allow densification to occur at temperatures as low as 950C without the need to the additions of excess lead oxides. The dielectric properties of the PZT ceramics prepared by reactive calcination route are measured and compared with the conventional route.     

Microwave Studies on Strontium Ferrite Based Absorbers

Single layer microwave absorbers based on strontium ferrite-epoxy composites have been fabricated and their reflection loss characteristics studied in the X-band (8–12.4 GHz) of microwave frequencies. Permittivity (_r – j_r) and permeability (_r – j_r) of Co and Ti added strontium ferrite SrCo _x Ti _x Fe_{12 – 2x} O₁₉ (x = 0.1 to 0.9 in steps of 0.2), have been measured. Thickness of the absorber is an important criterion influencing the absorption characteristics. Composites of 3 mm thickness are found to absorb over a reasonable range of X-band frequencies. A minimum reflection loss of –36.5 dB is observed for the composite with x = 0.3.     

低温烧结MgCuZn铁氧体的特性

根据低温烧结MgCuZn铁氧体电磁特性的有关文献报导,重点介绍了Cu2 含量对铁氧体烧结特性以及电磁特性的影响,讨论了MgCuZn铁氧体作为多层片式电感用磁芯材料的可能性.说明在910℃下烧结,CuO含量为12mol%的MgCuZn铁氧体具有非常高的电阻率、品质因数以及良好的频率特性,是制备高性能多层片式电感器的理想材料.     

微波烧结La掺杂CaCu3Ti4O12陶瓷的结构、介电和压敏性能

采用微波快速烧结法制备了La掺杂CaCu3Ti4O12致密陶瓷,研究了其结构、介电和压敏性能。所有Ca1-3x/2LaxCu3Ti4O12陶瓷均形成了CCTO晶相,但是La含量低于0.10时存在CuO第二相。随着La含量增加,Ca1-3x/2LaxCu3Ti4O12陶瓷介电常数随频率和温度变化越来越小;压敏电压逐渐增大,非线性系数也明显改善。其中La含量x=0.15时,Ca1-3x/2LaxCu3Ti4O12陶瓷具有良好的压敏性能:压敏电场强度为5.25 kV/cm,非线性系数为26.3。     

锰取代LiZn铁氧体的磁性能和介电性能研究

采用传统氧化物陶瓷工艺氧气烧结制备Mn取代的缺铁配方LiZn铁氧体,研究了Mn取代量对LiZn铁氧体磁性能和介电性能的影响。结果表明,随着Mn取代量的增加,饱和磁化强度Ms和剩余磁感应强度Br均呈先增大再减小的趋势,而矫顽力Hc先下降再升高;随着Mn取代量的增加,电阻率ρ逐渐下降,介电常数ε′变化不大,介电损耗角正切tanδε′总体呈增大趋势。     

Effect of CeO2 and Nd2O3 on the Microstructure and Microwave Dielectric Properties of (Zr0.8,Sn0.2)TiO4 Ceramics

(Zr_0.8,Sn_0.2)TiO₄ (ZST) ceramics were prepared by solid-state reaction method with 1 wt% ZnO and 0.5–1.5 wt% CeO₂ or Nd₂O₃ as sintering aids. The effect of processing parameters and additive concentration on the structure, microstructure and microwave dielectric properties of ZST ceramics were investigated. The dielectric constant (?_r) and temperature coefficient of the resonance frequency (τ_f) were not significantly affected by the addition of these additives. The unloaded quality factors (Q_u) were effectively promoted by CeO₂ and Nd₂O₃ additions. ?_r values of 40 and 38.3, Qxf_o values of 57,500 and 59,300 were obtained for the samples sintered with 1.5 and 0.5 wt% of CeO₂ and Nd₂O₃ respectively. The improvement in Qxf_o value is primarily attributed to the increase in uniform grain size and density.     

SrLnAlO4 (Ln=Nd and Sm) Microwave Dielectric Ceramics

SrLnAlO₄ (Ln=Nd and Sm) ceramics with K₂NiF₄ structure were prepared by a solid state reaction approach, and their microwave dielectric characteristics were evaluated together with the microstructures. The single phase dense SrNdAlO₄ and SrSmAlO₄ ceramics were obtained by sintering at 1450–1475°C and 1475–1500°C, respectively, and the good microwave dielectric characteristics were achieved: (1) = 17.8, Q · f = 25,700 GHz, _f = –9 ppm/°C for SrNdAlO₄; and (2) = 18.8, Q · f = 54,880 GHz, _f = 2 ppm/°C for SrSmAlO₄ dense ceramics. The Qf value significantly increased with increasing sintering temperature.     

烧结工艺对MnZn铁氧体磁性能的影响

在钟罩式气氛烧结炉中烧结高导MnZn铁氧体材料.研究发现,掺入适量的CaCO3和Bi2O3能改善材料的磁性能.烧结过程中烧结温度的增高可以促进晶粒长大,有利于提高起始磁导率;烧结气氛对离子电价和晶相形成有着决定性影响,选择合适烧结工艺是制备优质MnZn铁氧体的关键.     

电缆电容的计算

电容量是交流系统供电中整定计算的重要参数之一,介绍了一般情况下电缆电容的计算方法。     

微波烧结高介电常数钛酸钡复合材料的研究

分别采用微波烧结和传统烧结的方法对钛酸钡复合材料进行烧结。从微观结构、烧结后样品的收缩率、样品的电容以及介质损耗因数等几个方面进行了比较分析。结果表明：微波烧结比传统烧结得到的样品具有更致密、更均匀的微观结构。微波烧结对样品线性收缩率终值影响不大,但会增强烧结密度,使开始收缩温度降低20～25℃,得到的样品具有更小的介质损耗。     

材料性质对介质阻挡放电特性的影响

选取三种典型的介质材料：玻璃、环氧、聚四氟乙烯，通过试验研究它们的放电特性和介质厚度对放电特性的影响。结果表明阻挡层介质材料的选取对介质阻挡放电的特性有较大影响。试验和分析结果还显示了这样的规律，即选用介电常数较大、厚度较薄的材料容易产生强烈的放电。在理论上对这一试验结果给出了合理的解释．     

烧结温度对掺Mn的NiZn铁氧体磁性能的影响

研究了烧结温度对掺杂6wt% MnCO3的Ni0.24Zn0.6Fe1.98O4铁氧体磁性能的影响.实验发现,在1220℃烧结时,此配方NiZn铁氧体能达到较好性能,其起始磁导率及品质因数均高,介电常数高频衰减减小,且材料的微观结构较好,晶粒平均粒径较大,晶粒中气孔少.     

用溶胶-凝胶法制备的低温烧结Ti取代LiZn铁氧体

以柠檬酸为络合剂用溶胶-凝胶法制备了低温烧结Li0.5-0.5x+0.5yTiyZnxMnaFe2.5-0.5x-a-1.5yO4(0.15相似文献   

预烧温度和烧结温度对功率镍锌铁氧体磁性能的影响

用常规的氧化物法制备了功率NiZn铁氧体.研究了烧结温度与预烧温度对NiZn铁氧体性能的影响.实验发现,随着预烧温度和烧结温度的增高,起始磁导率先增大后降低,磁损耗则先降低后增大;在烧结温度为1265℃左右、预烧温度为900℃时,功率损耗达到最小,且起始磁导率达到了预期的要求.材料的微观结构较好,晶粒粒度较大.