石榴石铁氧体的介电常数与密度、饱和磁化强度和缺铁量的关系

采用普通陶瓷工艺制备了饱和磁化强度Ms为80~148 kA/m的小线宽石榴石铁氧体材料,按GB/T9633(等同IEC60556)标准)在10.7 GHz下测量了复合石榴石铁氧体的介电常数ε′和介电损耗角正切tanδ_ε。研究了e'与材料密度、饱和磁化强度Ms和缺铁量的关系。实验表明,e'随密度的增加而增大,随Ms的下降而减小,随缺铁量增加而降低。即,介电常数随着配方中代换离子的增加、Fe含量的减少而下降,说明了e'与Fe浓度密切相关。     

Co~(2+)取代对Ni铁氧体材料微波特性的影响

采用陶瓷工艺制备了Ni_(1-z)Co_z Fe_2O_4(0≤z≤0.04)微波铁氧体材料,研究了快弛豫离子Co~(2+)取代对Ni铁氧体材料微波性能的影响。结果表明,加入微量取代离子Co~(2+),随取代量的增大铁氧体材料的自旋波线宽ΔHk呈线性增大;材料的铁磁共振线宽ΔH先降后升,在Co含量为z=0.02时,材料ΔH出现最小值;Co~(2+)取代对材料的饱和磁化强度M_s、介电损耗的影响不大。     

BBSZ掺杂对X波段移相器用LiZn铁氧体材料磁性能的影响

通过在Li-Zn铁氧体材料中掺入H3BO3-Bi2O3-SiO2-ZnO(BBSZ)玻璃相(1~4wt%),利用氧化物法陶瓷工艺合成Li-Zn铁氧体材料。在900℃烧结获得了符合要求的Li-Zn铁氧体材料。讨论了材料的微观结构以及磁性能,包括饱和磁化强度Ms、矫顽力Hc以及剩磁比Br/Bm。结果表明,BBSZ掺杂能显著降低材料的烧结温度,饱和磁化强度Ms随BBSZ掺入量的增加先增大而后略微减小,矫顽力Hc随BBSZ掺入量的增加先明显减小而后略微增加。当BBSZ掺入量为1.5wt%时,可以获得最佳的综合性能。     

MoO_3掺杂对锰锌铁氧体显微结构与磁性能的影响

以Fe_2O_3、MnO、ZnO粉体为原料,采用固相烧结法,通过一次球磨,850℃预烧并掺杂,二次球磨,1200℃烧结最后压制成型制得不同MoO_3掺杂量的锰锌铁氧体,运用SEM、XRD、VSM等手段研究该材料的组织与性能。结果表明,无论是否掺杂MoO_3,均生成了典型的尖晶石铁氧体相和Fe_2O_3相。材料的饱和磁化强度和磁导率随掺杂量增加先增大后减小,矫顽力和剩余磁化强度先减小后增大。表现为掺杂0.06wt% MoO_3的锰锌铁氧块体组织最为致密,磁性能达到最优,矫顽力及剩余磁化强度最小,磁导率和饱和磁化强度最大。     

铁含量和热处理对溶胶-凝胶法制备的NiCuZn铁氧体材料磁性能的影响

用溶胶-凝胶法制备Ni0.4Cu0.2Zn0.4FexO4尖晶石铁氧体纳米粉体,经过750℃的热处理后即有尖晶石相形成。详细研究了铁含量和热处理温度对静态磁性能的影响。粉料经造粒、压环成型并进行烧结,测量了它们的静态及交流磁性能。结果显示,在温度1000℃烧结3h,随x增大,材料矫顽力先变小后变大,而比饱和磁化强度先变大后变小,x=2.0的材料静磁性能较好,矫顽力为120A/m(1.5Oe),比饱和磁化强度为79.5 A.m2/kg。x=1.8的材料的起始磁导率最高,接近125,截止频率约为20MHz。随x增大,磁导率降低、截止频率提高,材料的高频特性有所改善。     

烧结温度对镍锌功率铁氧体磁性能的影响

为得到Zn含量不同时NiZn铁氧体材料的最佳烧结温度,用氧化物法制备了NiZn铁氧体材料,研究了烧结温度对材料起始磁导率、功耗、饱和磁感应强度和微结构的影响.结果表明,适宜的烧结温度对制备功耗低、饱和磁感应强度高和较优起始磁导率的NiZn铁氧体材料至关重要,而Zn含量不同时对应材料的最佳烧结温度也各不相同.     

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   

低MS大功率石榴石型旋磁铁氧体材料研究进展

钇铁石榴石(YIG)型多晶铁氧体是适用于低波段大功率微波器件的主要旋磁材料.本文对近年来国内外石榴石型旋磁铁氧体材料的研究进展进行了综述,就通过YIG晶格中阳离子置换实现对铁氧体饱和磁化强度及其温度系数的调控、以及通过多晶显微组织结构优化实现铁氧体材料低损耗与高功率性能等方面进行了分析与讨论.     

Zn含量对NiZn铁氧体材料微观结构及磁性能影响

采用固相反应法制备NiZn铁氧体材料,研究了配方中ZnO含量对材料微观结构及磁性能的影响.结果表明,ZnO在固相反应法制备NiZn铁氧体材料过程中有助熔作用,增大Zn含量,材料的晶粒尺寸增大,但均匀性变差;同时,非磁性Zn2+增多,材料的起始磁导率显著增大,但因居里温度过低,饱和磁感应强度和矫顽力均显著降低.     

文摘及索引

1、微波铁氧体Microwave ferrites,Electronic components Vol.13,No.22,P.1089,1972. 本广告列出了马可尼通讯系统有限公司制备的铁氧体材料的性能。Y-70A系列的微波材料饱和磁化强度在20℃时为1900G,此为石榴石材料的目前最高值。掺铝的石榴石铁氧体的线宽为5-25奥斯特。此值为一般的掺铝石榴石材料的值的1/2或1/5。     

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。     

小量偏离正分对多晶石榴石材料基本性能参数的影响

用普通陶瓷工艺制备了不同饱和磁化强度的一系列石榴石材料Y3-aRaFe5-bMebO12,测试了从富铁(缺钇)到缺铁(富钇)整个范围内每种材料的基本参数.研究了小量偏离正分(偏离量小于0.15)对石榴石材料基本性能参数的影响,并分析了材料介电损耗在富铁和富钇情况下的变化趋势差别如此巨大的原因.研究表明,对于小量偏离石榴石材料来说,介电损耗和剩磁比是最敏感的两个参数,而介电常数是最不敏感的参数.     

微波铁氧体介电常数测量值的尺寸因素修正

用普通陶瓷工艺制备了饱和磁化强度M_s为96 kA/m的钇钙钒石榴石铁氧体材料,在10.7 GHz下按照GB9633(等同IEC60556标准)测量了石榴石铁氧体的介电常数ε'及介电损耗tanδ_ε。实验表明测得的ε'值随试样直径的减小而降低。由计算公式分析了ε'随试样直径减小而降低的原因。给出了ε'测量值与试样直径关系的经验公式及ε'的尺寸修正系数,修正以后可以基本上消除ε'测量值中由试样尺寸引起的误差。最后讨论了介电常数和介电损耗的精准测量问题。     

Correctly accounting for radiofrequency spillover in saturation transfer experiments: application to measurement of the creatine kinase reaction rate in human forearm muscle

Measurements based on transfer of magnetization have been widely used to calculate reaction rates in systems with slow chemical exchange. In these experiments, correction for direct irradiation of the observed resonance is in general accomplished by replacing the equilibrium magnetization in the Bloch equations by a magnetization obtained in an experiment in which a low power radiofrequency (RF) pulse is placed contralaterally, that is, at an equal distance from the observed resonance as the saturated one but on the opposite side. However, the magnetization observed during contralateral irradiation is affected not only by direct irradiation but also by chemical exchange. We demonstrate here that including this effect leads to a substantial improvement in the accuracy of reaction rate determination in steady-state saturation transfer experiments and, if incomplete saturation is present, also in transient saturation transfer experiments. In steady-state saturation trnasfer experiments performedin vivo at 1.9 T, correct interpretation of the contralateral saturation transfer experiment resulted in a correction of the creatine kinase reaction rate by approximately 11% on average.     

Multiferroic ceramics Pb(Fe1/2Nb1/2)O3 doped by Li

We present the results of obtaining and investigating multiferroic ceramics Pb(Fe_1/2Nb_1/2)O₃ (PFN) and PFN doped by various amounts of Li (PFN:Li). Ceramics have been obtained from oxides by two-step synthesis. For obtained samples the X-ray diffraction patterns, microstructure, DC electric conductivity, the temperature dependencies of dielectric permittivity and dielectric losses, electromechanical properties and hysteresis loops have been investigated. Obtained results have shown that the introduction of Li decreases electric conductivity and improves dielectric and electromechanical parameters important for applications.     

Investigation on the Dielectric and Polarization Behavior of Sol-Gel Derived Erbium Doped Pb(Zr 0.53 Ti 0.47 )O 3 Thin Films

We have studied the effect of Er 3+ doping on the dielectric and polarization hysteresis behavior of sol-gel derived Pb 1.05 (Zr 0.53 Ti 0.47 )O 3 thin films. Up to 1 at% Er doping, the dielectric constant of undoped PZT increases from 1245 to 1477 (measured at 50 kHz, 500 mV oscillation voltage), whereas the remnant polarization increases from 30 to 41 w C/cm 2 . Under the subswitching external field, the dielectric permittivities follow the Rayleigh law. The Rayleigh coefficient ( f ) was considered as a measure of the ease of domain wall motion. Up to 1 at% Er doping, the increase of f indicates minimal defect-domain wall interaction due to lower defect concentration. Under the switching field, the irreversible part of the switchable polarization was estimated from the C-V and hysteresis measurements. At the saturation field it was observed that up to 1 at% Er doping the irreversible component at switchable polarization increases and reversible component remains low. The improvements of dielectric and ferroelectric properties for up to 1 at% Er doping have been correlated to the relative site occupancy of Er 3+ as a function of Er content in PZT host lattice.     

Structure and properties of Zn-doped CoFe2O4 thin films via a sol–gel method

Zn-doped cobalt ferrite Co_0.9Zn_0.1Fe₂O₄ (CZFO) films with the spinel structure were fabricated on Pt(111)/Ti/SiO₂/Si(100) using a sol-gel method, and the effect of annealing temperature and time on structure and magnetic properties of the CZFO thin films were investigated. The coercivity and saturation magnetization of the films are not sensitive to annealing time, and increase with a rise in the annealing temperature below 800 °C. The CZFO thin films annealed at 800 °C show the best crystallization and the highest coercivity (3.5 kOe), and above 800 °C, the coercivities of the films decrease as a result of formation of multi-domains, while the saturation magnetization comes to stable.     

溶胶凝胶法制备Li_4Ti_5O_(12)/C负极材料及电化学性能

采用溶胶凝胶法,以有机物钛酸四丁酯和醋酸锂为原料,草酸为螯合剂,PEG为碳源制备出Li_4Ti_5O_(12)/C复合材料前驱体,在N_2气氛中850℃高温煅烧制备出Li_4Ti_5O_(12)/C复合材料。通过XRD、SEM分析表明,850℃下煅烧10 h合成结晶性良好的亚微米级纯相尖晶石钛酸锂。电化学性能测试结果表明,Li_4Ti_5O_(12)/C在0.2C,1C,2C倍率下的首次放电比容量分别为173.3、168.7、166.3 mAh/g。与Li_4Ti_5O_(12)相比,显示出良好的倍率性。     

锂二次电池正极材料Li4Ti5O12的研究

用不同的TiO2原料,在相同的实验条件下固相合成了锂二次电池正极材料Li4Ti5O12.电化学测试结果表明,由介孔TiO2原料合成的Li4Ti5O12正极材料表现出更好的电化学性能.在0.2 C倍率放电时,介孔TiO2原料合成的Li4Ti5O12可获得较高的比容量,达162.1 mAh/g,而且通过65个循环后,在2C...