镍锌铁氧体材料的特性、工艺与添加改性

主要阐述了Ni-Zn软磁铁氧体材料的研究现状和发展.介绍了制备方法、烧结工艺、主成分配方和添加剂对Ni-Zn软磁铁氧体性能的影响,国内外的研究表明,烧结工艺是制备高性能铁氧体材料的关键,主成分配方是影响铁氧体材料性能的决定性因素,添加剂是改善和提高铁氧体材料性能的有效措施之一.     

NiZn系软磁铁氧体材料的种类及应用

NiZn系软磁铁氧体是尖晶石铁氧体材料中的一个重要分支.NiZn系铁氧体材料以其电阻率高、烧结工艺简单、高频性能好等特点而获得广泛应用.本文简要介绍了当前应用前景较好的几类NiZn铁氧体材料及其应用,包括抗EMI系列铁氧体材料、射频宽带NiZn铁氧体材料、功率型NiZn系铁氧体材料和低温烧结NiCuZn铁氧体材料等,同时展望了各自的发展前景.     

微波烧结高磁导率Mn-Zn铁氧体材料的研究

介绍了利用微波烧结技术小批量生产高磁导率Mn-Zn铁氧体的烧结工艺与设备.结果表明,微波加热方式不但大大优于传统加热方式,且利用微波烧结技术烧结的高磁导率Mn-Zn铁氧体材料的各项性能均达到或超过传统烧结方式的产品.     

软磁铁氧体烧结专用设备--钟罩式气氛烧结炉的研制

自行研制开发了新一代软磁铁氧体烧结设备--钟罩式气氛烧结炉.它采用全纤维高温炉衬、分区分组加热、循环强制冷却、计算机全自动控制等技术,具有批次产量大、温度和气氛均匀性好、控制精度高、产品一致性高、操作使用灵活等优越特性.特别适用于锰锌高导软磁铁氧体和低功耗软磁铁氧体等高档铁氧体材料的气氛烧结.     

比表面积测试仪和热分析仪在软磁铁氧体质量控制中的应用

在软磁铁氧体材料的生产中,粉料活性(比表面积)对生产工艺和材料性能有重要影响,烧结是影响材料性能的关键工序之一.本文概述了比表面积测试仪和热分析仪在软磁铁氧体生产质量控制中的应用.     

旋转底式软磁气氛烧结炉的开发与设计

自行研制开发了新一代软磁铁氧体烧结设备--旋转底式气氛烧结炉,它采用旋转底盘、全纤维高温炉衬、分区分组加热、循环强制冷却、计算机全自动控制等技术,具有批次产量大、温度和气氛均匀性好、控制精度高、产品一致性优、操作使用灵活等优越特性.特别适用于高磁导率锰锌铁氧体和低功耗软磁铁氧体等高档铁氧体材料的气氛烧结.     

旋磁铁氧体材料的微波烧结及在环行器中的应用研究

对微波烧结旋磁铁氧体材料进行了初步实验,检测和分析了烧成的材料和由其制成的环行器的主要技术参数,并与传统烧结材料进行了对比.结果表明,微波烧结旋磁铁氧体材料介电损耗较低,用其制作的环行器满足设计要求,损耗减小.该烧结方法具有一定的优越性.     

片式抗电磁干扰滤波器Ni-Zn铁氧体材料与工艺研究

通过添加适量CuO和Bi2O3，将Ni-Zn铁氧体材料的烧结温度降至870—920℃，达到Ni-Zn铁氧体材料与Ag电极共烧匹配的目的。试制了片式抗电磁干扰滤波器，并对其插入损耗特性进行了计算机模拟，表明所研制的抗电磁干扰滤波器不仅适合高密度表面封装技术的要求，也可满足宽频域抗电磁干扰需要。     

用精矿粉和Mn3O4制备性能优良的软磁MnZn铁氧体

用精矿粉代替Fe2O3,用Mn3O4代替MnCo3制备了性能优良的软磁MnZn铁氧体材料，采用合适的配方及烧结工艺能进一步提高样品磁性能。     

微波铁氧体饱和磁化强度的测量磁场及剩磁比问题

微波铁氧体的饱和磁化强度Ms是器件设计者选择材料的重要参数之一,但是一些文章常将Bm、Bs与Ms混为一谈,本文旨在讨论这一问题。软磁铁氧体材料因为磁晶各向异性常数K1非常低,饱和磁化场Hs低,其Bs通常由指定测量磁场Hm下测得的Bm(Hm Hs)来确定。为了说明微波铁氧体与软磁铁氧体的不同,给出了小线宽石榴石材料的磁化曲线和微波铁氧体材料的矫顽力,由此推知微波铁氧体材料的饱和磁化场Hs远高于磁滞回线的测量磁场Hm(5Hc 10Hc),相差2 3个数量级。由Li铁氧体的Bm/0Ms(Mm/Ms)63%81%和Mn:YIG的Bm/0Ms 81%86%,说明在Hm下材料磁畴中的磁矩中有14%37%不在磁场方向。因此对微波铁氧体来说,不能像在软磁铁氧体中那样有Bm Bs 0Ms的关系。所以为保证材料被磁化饱和,Ms的测量应该按照IEC60556标准在>300kA/m磁场下进行。最后讨论了经常将剩磁比R=Br/Bm误成Br/Bs问题。     

Sr-Ca-La-Co型六角铁氧体微波与传统预烧工艺比较研究

在实验室采用微波预烧(MC)和传统马弗炉预烧(CC)两种方法制备了M型六角铁氧体预烧料,然后制备出烧结磁体。采用XRD、SEM和VSM分析样品的结构特征、微观形貌及磁特性。研究表明,MC技术能快速有效地生成六角铁氧体永磁材料,且能提升材料的Br和Hc J。对于配方Sr0.22La0.38Ca0.4Fe11.6Co0.24O19,当预烧温度和烧结温度分别为1250℃和1170℃时,对应MC预烧料的烧结样品的Br=444m T和Hc J=415k A/m,与相同温度下的CC预烧料的烧结样品指标相比分别提高1.6%和5%。     

Electrical properties of conventional and microwave sintered lead free magnetoelectric composites

Abstract

Here we report comparison of dielectric properties of composition synthesized by microwave and conventional sintering. Microwave sintering requires less time and temperature to achieve the same quality of materials as sintered by conventional route. The material sample was prepared by conventional solid state method and sintered in conventional & microwave furnace. Sintered samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. The dielectric and ferroelectric properties were recorded for both the samples and properties were found to improve in microwave sintered samples. There is also a significant improvement in density by microwave processing.     

微波频段用高磁导率铁氧体薄膜研究进展

主要介绍了微波频段用的高磁导率铁氧体薄膜近年来的研究进展。尖晶石铁氧体薄膜的重点集中在Ni-Zn和Li系材料上,介绍了旋转喷涂法以及Co2 掺杂对薄膜微波磁性的影响,并分析了微波频段高磁导率机理;对于六角晶系铁氧体薄膜,重点叙述了衬底层对BaM六角结构形成的影响以及BaCoxTixFe12-2xO19铁氧体薄膜的共振特性,也对(Zn1-xCox)2-W铁氧体薄膜作了适当介绍。最后,讨论了目前存在的问题和发展前景。     

射频宽带LTN_2B NiZn铁氧体材料的研制与特性

采用传统氧化物工艺结合复合掺杂制备Ni_xZn_(1-x)Fe_2O_4铁氧体材料,采用适当的技术措施优化工艺.根据磁导率和居里温度随锌含量的变化,确定出满足设计指标要求的成分x=0.36,选择合理的烧结温度,制备出综合性能较优、牌号为LTN2B的优质镍锌铁氧体材料, 达到了设计指标.其起始磁导率μ_i为2188、居里温度T_C为136℃、饱和磁感应强度B_s为319 mT,可望应用于射频宽带抗EMI滤波器.     

Microwave Hydrothermally Synthesized Nanocrystalline Co-Zn Ferrites

Co-Zn ferrite nano-powder was synthesized using the Microwave- Hydrothermal (M-H) method. The powder was characterized using X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared spectroscopy (FT-IR). The densification of nanoferrites was done using two methods: a) conventional and b) microwave sintering. Electrical and magnetic properties of the sintered samples were measured at room temperature. Electrical properties such as dielectric constant (?'), dissipation factor (D), initial permeability (μ_i) and quality factor (Q) were measured over a wide frequency range (10 kHz to 1 MHz). The Curie temperature has been determined from the permeability versus temperature plots. It was found that the enhanced electrical and magnetic properties were observed for microwave sintered samples.     

Effect of microwave sintering on structural, morphological and dielectric properties of Ba(FeNb)0.5O3 ceramics

Polycrystalline Ba(FeNb)_0.5O₃/BFN ceramics were sintered conventionally and in a microwave (MW) furnace, respectively. Conventional and microwave sintering temperatures were same with different soaking times. Microwave sintering of BFN ceramics showed enhanced grain growth with improved dielectric properties. Highest dielectric constant (~29,913 at 1 kHz) at room temperature (RT) was observed in BFN ceramics sintered in MW furnace for 30 min. At RT, a non-Debye type of dielectric relaxation was observed in both conventionally and MW sintered BFN ceramics. The observed giant dielectric constant of conventionally and MW sintered BFN ceramics was attributed to intrinsic (space charge polarization) and extrinsic (Maxwell-Wagner type polarization) effects, respectively.     

Electromagnetic shielding properties of soft magnetic metal and ferrite composites for application to suppress noise in a radio frequency range

Electromagnetic shielding properties of soft magnetic metal alloy (Fe-Al-Si) flakes and Ni-Zn ferrite composites for effective suppression of broadband and high frequency noise were investigated. In the soft magnetic composites, the maxima of reflection loss were shifted to high frequency with increase in content of Ni-Zn ferrite. The composites with content of 50 and 70% ferrite exhibited broadband absorptive characteristics. The broadband character- istics might be caused by the extended resonance due to an overlap between imaginary permeability and permittivity of the two composites over the frequency range from 2 to 10 GHz.     

组合掺杂对低温烧结NiZn功率铁氧体功耗特性的影响

采用陶瓷工艺制备低温烧结Ni Zn软磁铁氧体材料,研究了掺杂Co_2O_3、Cu O、Bi_2O_3、V_2O_5、Si O_2等对材料烧结温度及主要磁性能如磁导率、功耗等的影响。结果表明,Bi2O3对降低材料烧结温度有益但对功耗改善无益,Si O2对功耗改善有益但效果不明显,而组合添加0.15mol%Co2O3、9.0mol%Cu O、0.40~0.50wt%V2O5不仅可达到大幅度降低材料功率损耗,改善功耗特性,而且可保证材料低温烧结和其它优良磁性能,并获得具有低温烧结(烧结温度900℃左右)、低功耗(功率损耗Pcv≤300k W/m3(20℃,1MHz,30m T))、适于LTCF工艺和片式功率器件应用的Ni Zn功率铁氧体材料。