掺铁氧体和SiC纤维水泥基复合材料的吸波性能

用溶胶凝胶法制备了W型Ba(Zn1-χCoχ)2Fe16O27六方铁氧体,并以铁氧体和短切SiC纤维与水泥复合,制备了水泥基复合材料.测量了该材料的电磁参数,并计算了该材料对电磁波的反射率.结果表明:χ为0.8时,W型Ba(Zn1-χCoχ)2Fe16O27六方铁氧体的吸波性能最好,该铁氧体的掺量(质量分数)为35%和短切SiC纤维掺量(质量分数)为0.2%时,水泥基复合材料在12～18GHz范围内具有最大反射率-13.5dB,有效带宽达到4.7GHz.     

V2O5含量对MoO3-V2O5复合添加NiCuZn铁氧体性能的影响

用传统陶瓷工艺制备了(Ni.016Cu0.2Zn0.64O)1.02(Fe2O3)0.98铁氧体材料,研究了MoO3-V2O5复合添加对烧结特性和磁性能的影响.结果表明,复合添加MoO3-V2O5能促进样品致密化,提高起始磁导率,并能降低功耗.当MoO3为0.15wt%、V2O5为0.15wt%时,930℃烧结起始磁导率(μ＞800)、功耗(305kW/m3)、密度(5.12g/cm3)都达到较大值.其值比同样配方只掺杂MoO3的NiCuZn材料明显提高.     

(Ba1-xSrx)3Co2Fe24O41材料的磁化处理与烧结特性

研究了采用固相法制备的(Ba1-xSrx)3Co2Fe24O41材料的烧结特性,讨论了预烧工艺、烧结温度、保温时间、降温方式等与材料显微结构及性能的关系。为了展宽频带,将永磁铁氧体制造中的磁化处理工艺“移植”到了该材料的制备中。结果显示：引入磁化处理措施有望改善材料性能。引入磁化处理后,优化的制备条件为配合料经1200℃预烧2h,升温速度为1℃／min;样品在1220～1240℃烧结1～3h,缓慢降温,所制得的样品共振频率高达1．8GHz以上,截止频率在1GHz附近,起始磁导率在5～13之间。介电常数ε低于30。     

甚高频段应用的Co2-Z型铁氧体材料研究

采用普通陶瓷工艺，制备了适用于甚高频段（UHF）的Co2-Z型六角晶系铁氧体材料。通过测量这种材料的复数磁导率μ的频散特性，发现其共振频率可达3GHz以上。测试不同烧结温度下的样品的磁谱表明，随着烧结温度的上升，复数磁导率μ的实部μ'上升，但共振频率fr和截止频率fc均下降。SEM照片显示，这是由于晶粒随烧结温度升高而长大所致。     

低温烧结Mg_4Nb_2O_9微波介质陶瓷(英文)

分别研究了不同含量Li2CO3/V2O5共掺杂和部分Li取代Mg对Mg4Nb2O9基陶瓷烧结特性、显微结构和微波介电性能的影响.结果表明:Li2CO3/V2O5共掺杂或部分Li取代Mg,均能使Mg4Nb2O9基陶瓷的烧结温度从1 400℃降至950℃,但其烧结机理不同.Li2CO3/V2O5共掺杂Mg4Nb2O9(MNLV)样品中的低熔点液相,使MNLV陶瓷的致密化烧结温度降低.部分Li取代Mg显著降低了(Mg(4-x)Lix)(Nb1.92V0.08)O(9-δ)(MLNV)样品的致密化烧结温度.950℃烧结,相对于MNLV样品的品质因数(Q=13276)而言,MLNV样品的Q值(1 759)显著恶化,这是由于Li1+占据Mg2+晶格.使晶体中非谐振项损耗增加.     

共沉淀法制备Co2-Z型铁氧体形成动力学过程研究

用化学共沉淀法制备得到了Z型六角铁氧体,并研究了它的动力学过程;详细讨论了煅烧制度,如煅烧温度、升温速率和却冷方式对最终产物晶体结构的影响.研究表明:Co2-Z型六角铁氧体的生成序为:Ba-M→Ba-M + Co2-Y→Co2-Z;在1200℃下煅烧4h,可获得以Co2-Z为主晶相的铁氧体材料;升温速率及冷却速率对晶体的形成与结构有影响,快速升温影响最为明显.     

SiO2·Bi2O3对NiZn铁氧体的烧结和磁性能的影响

本文采用溶胶-凝胶法制备NiZn铁氧体-SiO2·Bi2O3复合材料。结果表明:烧结过程中Bi2O3与SiO2形成非晶态玻璃相促进烧结,使瓷体烧结温度降至1030℃,并且瓷体的磁导率随非磁性玻璃相的增加显著减少。磁导率的变化主要是由于非磁性相的引入导致磁路隔断、退磁场增加以及铁氧体晶粒减小所致。加入适量非磁性相有助于改善瓷体的高频特性。     

水热法制备NiFe2O4-BaTiO3复合材料及其电-磁性能

本文利用水热法以铁酸镍和钛酸钡为原料,制备了具有尖晶石结构的铁酸镍(NiFe2O4)和钙钛矿结构的钛酸钡(BaTiO3)复合材料,利用X射线衍射(XRD)和扫描电镜(SEM)对样品的物相和形貌进行了分析。研究了复合样品的介电常数和磁导率随频率和温度的变化。结果表明:复合样品中的钛酸钡在烧结后由四方相转变成六角结构;生成六角结构的钛酸钡颗粒和类球状铁氧体颗粒;介电常数和磁导率随铁氧体含量的增加逐渐增大,复合陶瓷的介电居里温度随铁氧体含量的增加向低温方向移动,磁性居里温度随铁氧体含量的增多向高温方向移动,逐渐接近铁氧体的居里温度。     

Mn掺杂对Ni-Cu-Zn铁氧体烧结的影响研究

采用微波水热法制备(Ni0.30Cu0.20Zn0.50)Fe2O4·xMnO(x=0,0.1,0.2,0.3,0.4)铁氧体粉末,压制成型,在750℃、850℃、900℃下,烧结形成致密的陶瓷体。用XRD、SEM对烧结体的相结构和显微结构进行了研究。结果表明:掺Mn有利于提高Ni-Cu-Zn铁氧体烧结密度,改善微观结构。     

生产高性能网络变压器磁芯的关键技术

随着网络的广泛使用,网络变压器的用量越来越多。网络变压器磁芯对铁氧体材料的要求是宽温高增量磁导率μΔ。生产高性能网络变压器磁芯的关键技术是:选择一个BS和μi双高的配方、添加适量的Co2O3和Nb2O5、在合适氧分压下用较低温度烧结。     

Low-Temperature Sintering and Electromagnetic Properties of Copper-Modified Z-type Hexaferrite

The influence of the substitution of copper for cobalt on the low-sintering densification, microstructure, lattice parameters, and electromagnetic properties of planar Z-type hexaferrites, which have a stoichiometric composition of Ba₃Co_{2(10.8− x )}-Zn_0.4Cu_{2 x} Fe₂₄O₄₁, were investigated. The experimental results show that densification of the copper-substituted hexaferrite is dependent on the amount of copper substitution and sintering temperatures. XRD analysis reveals that the solid solubility of copper in Z-type hexaferrite is limited to x ≤ 0.30. At the same time, the lattice parameters ( a and c ) of Z-type hexaferrites with copper substitution showed a small change, that is, decrease of a parameter in the basal plane and increase of the c axial. Moreover, the microstructure becomes more homogeneous and intragranular pores decrease considerably, but the temperature-stable range of the Z-type phase formation is narrow. The copper-substituted hexaferrites, with x = 0.20 and sintered at ∼1125°C for 4 h, resulted in a high density sample of ∼4.68 g/cm³ as the optimal value, good magnetic properties, and the enormous potentiality for fabrication of multilayer chip inductors used in hyper-frequencies.     

Low-temperature sintering and high frequency properties of Cu-modified Co2Z hexaferrite

The low temperature sintering behaviors and high frequency properties of Cu-modified Co₂Z hexaferrites have been investigated. Normally, Cu-modified Co₂Z hexaferrite is difficult to be sintered at temperature lower than 1150 °C. By adding a small amount of sintering aid Bi₂O₃, Cu-modified Co₂Z ceramics with high density (more than 95% theoretical density) have been prepared successfully after sintering below 900 °C. The microstructures and properties are significantly influenced by the sintering temperature, the amount of Bi₂O₃ addition, as well as Cu content. The modified hexaferrite ceramics sintered at 900 °C, exhibited excellent high frequency properties, such as high initial permeability up to 6.6, high quality factor more than 30, high resistivity over 10⁹ Ω cm and good thermal stability. The experimental results show that these materials have a great potential as soft magnetic media for high frequency MLCIs applications.     

Low-Temperature Sintering, Densification, and Properties of Z-type Hexaferrite with Bi2O3 Additives

The effect of the addition of Bi₂O₃ on the densification, low-temperature sintering, and electromagnetic properties of Z-type planar hexaferrite was investigated. The results show that Bi₂O₃ additives can improve the densification and promote low-temperature sintering of Z-type hexaferrite prepared by a solid-state reaction method. The presence of Bi₂O₃ in the grain boundaries and the generation of Fe²⁺ degrade the initial permeability of the samples but make the quality factor and cut-off frequency increase. Various possible mechanisms involved in generating these effects were also discussed.     

Novel method for low temperature sintering of barium hexaferrite with magnetic easy-axis alignment

Most applications of hexaferrites require sintered products, but sintering of hexaferrites at high temperatures degrades their magnetic properties and cannot be used as low-temperature co-fired ceramics. Additionally, due to the magnetic uniaxial anisotropy of hexaferrites, excellent magnetic properties are attained when the particles are aligned along the magnetic easy-axis. In order to overcome these problems, herein we suggest a new method to decrease the sintering temperature and improve the simultaneous alignment of magnetic particles along the easy-axis. NaCl-barium hexaferrite particles and NaCl-amorphous particles were sintered using the spark plasma sintering process. Using this method, a sintered body with a relative density of 92.5% and 70.2% alignment was fabricated at 800 °C for 5 min. In this method, the added NaCl played a significant role in facilitating the low temperature sintering and particle alignment. This method was found to be effective for low temperature sintering and nano-scale particle alignment.     

低温烧结CuO-V_2O_5-Bi_2O_3掺杂Zn_3Nb_2O_8陶瓷的微波介电性能

研究了CuO–V2O5–Bi2O3作为烧结助剂对Zn3Nb2O8陶瓷的烧结特性、微观结构、相结构及微波介电性能的影响。CuO–V2O5–Bi2O3复合掺杂可以将Zn3Nb2O8陶瓷的烧结温度从1150℃降到900℃。在900℃烧结4h的Zn3Nb2O8–0.25%(质量分数,下同)CuO–1.5%V2O5–1.5%Bi2O3陶瓷的密度达到了理论密度的98.1%,相对介电常数为18.8,品质因数与谐振频率之积为39442GHz。该体系的介电性能和陶瓷的致密度与烧结助剂的含量及烧结温度密切相关,陶瓷的致密度和相对介电常数随CuO–V2O5–Bi2O3烧结助剂含量的增加而增加,同样陶瓷的致密度和相对介电常数也随烧结温度的升高而提高。     

Soft Ferrite Materials for Multilayer Inductors

Various families of soft ferrites (Ni–Cu–Zn; Mg–Cu–Zn; Co₂–Z; Mn–Zn) with a sintering temperature of T ≤950°C are used for multilayer inductors. It is shown for Ni–Cu–Zn and Mg–Cu–Zn ferrites that composition, powder particle size, and sintering additive concentration strongly affect the shrinkage, sintering behavior, microstructure, and magnetic properties. A maximum permeability of μ _i =700–900 is observed with a Bi₂O₃ addition of about 0.5 wt%. The maximum shrinkage can be shifted down to 700°C using nanosize powders. Z-type hexaferrites with a permeability of 10 are used for high-frequency applications up to 2 GHz.     

The effect of Zn ion substitution on electromagnetic properties of low-temperature fired Z-type hexaferrite

The influence of Zn substitution on the densification, microstructure, lattice parameters and electromagnetic properties of planar Z-type hexaferrites, which have stoichiometric composition of Ba₃Co_2(10.8−x)Zn_2xCu_0.4Fe₂₄O₄₁, were investigated. The results show that the Zn²⁺ substitution has no obvious effect on the densification, but Z-type hexagonal phase can form and demonstrate typical planar anisotropic characteristics of soft magnetic materials (σ_r6.20 emu/g) in the range of x0.25. The of lattice parameters of planar a (0.588 nm) and axial c (5.25 nm) remain stable. At the certain temperatures, the sintered hexaferrites with an optimal density of about 4.62 g/cm³ show better electromagnetic properties for x=0.15 than the samples without Zn²⁺ incorporation: initial permeability of about 9.0, cut-off frequency of above 800 MHz, resisitivity of above 3.20 Ω cm and dielectric constant of less than 35.     

Nb2O5掺杂ZnO超高致密度陶瓷靶材的制备

采用传统的固相烧结技术制备了Nb2 O5掺杂ZnO陶瓷靶材,研究了不同烧结温度、Nb2 O5掺杂量对NZO靶材的电学性能、相对密度、抗弯强度的影响.结果表明:当烧结温度1200℃,Nb2 O5的掺杂量为0.4wt%时,其综合性能最佳,此时靶材电阻率为0.189Ω·cm,相对密度为99.46%,抗弯强度141.74 MPa.     

Sb2O5和Bi2O3添加剂对Ag(Nb1-xTax)O3陶瓷结构、形貌和性能的影响

研究了Sb2O5和Bi2O3添加剂对Ag(Nb1-xTax)O3陶瓷材料的结构、形貌和介电性能的影响.结果表明:当Sb2O5和Bi2O3的质量分数较少(＜2.5%)时,不会影响Ag(Nb1-xTax)O3的钙钛矿结构,但能促进其烧结,使所得陶瓷样品更均匀致密.添加适量的Sb2O5和Bi2O3均可使Ag(Nb1-xTax)O3的介电常数(ε)增大,介电损耗(tgδ)减小,介电性能的温度稳定性得到改善.Bi2O3较Sb2O5对降低Ag(Nb1-xTax)O3陶瓷损耗及改善温度稳定性的效果更佳.     

Sb2O3掺杂对ZnO压敏陶瓷晶界特性和电性能的影响

制备了掺有Sb2O3不同掺杂量ZnO压敏陶瓷样品,采用扫描电镜对样品进行显微结构分析,研究了Sb2O3掺杂浓度对ZnO压缩电阻显微结构和性能的影响,测量了样品的电性能,由样品C－V特性的测量计算出晶界参数,并由此讨论了陶瓷性能与晶界特性的相关性。研究发现,在ZnO压敏陶瓷样品中掺杂适量的Sb2O3可以提高ZnO压敏陶瓷样品的非线性性能,但当Sb2O3的摩尔分数超过0．088％时,电性能反而优化,这是因为Sb2O3掺杂浓度不同会引起晶界势垒高度、施主浓度与陷阱密度的变化,因此Sb2O3掺杂量要控制在适当的范围内。