PrxTb0.2Dy0.8-xFe1.85C0.05合金的结构和磁致伸缩

用电弧炉熔炼法制备了Prx Tb0.2Dy0.8-x Fe1.85C0.05(x=0.1~0.4)合金。分别采用X射线衍射(XRD)、金相显微镜、振动样品磁强计(VSM)和应变仪分析了合金的结构、金相、居里温度和磁致伸缩。研究发现x≥0.2时,合金中出现了RFe3相和稀土相;居里温度随着Pr含量的增加表现为下降趋势;合金Pr0.2Tb0.2Dy0.6Fe1.85C0.05表现出了较为优良的磁致伸缩特性。     

粘结剂含量对(Pr_(0.8)Tb_(0.2))(Fe_(0.4)Co_(0.6))_(1.88)C_(0.05)合金粘结样品磁致伸缩的影响

用HDDR工艺制备Tb0.2Pr0.8(Fe0.4Co0.6)1.88C0.05合金粉末,用不同的粘结工艺制备粘结样品,用电阻应变片方法测量样品的磁致伸缩性能。结果表明,对不同粘结剂配比的棒状样品,当模压压力为420 MPa、粘结剂含量为8%、磁场强度为9 kOe时,样品的磁致伸缩最大(λa=533×10-6);随粘结剂的增加或减少,样品的磁致伸缩均降低;粘结样品的密度随粘结剂含量的增加而减少。     

合金Pr0.1Ce0.6Tb0.3Fe1.9-xBx的结构和磁致伸缩

用电弧炉熔炼法制备了Pr0.1Ce0.6Tb0.3Fe1.9-xBx(x=0.00～0.20)合金.分别采用X射线衍射(XRD)、振动样品磁强计(VSM)和应变仪分析了合金的结构、居里温度和磁致伸缩.研究发现,所有样品均呈现单一MgCu2型Laves相结构;随B含量的增加,晶格常数在x≤0.1时缓慢下降而在x ＞0.1...     

La0.7-xSmxSr0.3MnO3体系的磁电性质和磁致伸缩效应

用固相反应法制备了La0.7-xSmxSr0.3MnO3(x=0、0.1、0.2、0.3、0.4、0.5、0.6)多晶材料,研究了它们的磁电性质及室温下的磁致伸缩效应.结果表明,随着Sm掺杂量的增加,样品的晶体结构从菱面体相转变为正交相,居里温度下降.在结构转变点附近,样品室温磁致伸缩效应出现极大值.样品在室温下的磁致伸缩主要来源于材料中的交换磁致伸缩.     

粘结剂含量对(Pr0.8Tb0.2)(Fe0.4C00.6)1.88C0.05合金粘结样品磁致伸缩的影响

用HDDR工艺制备Tb0.2Pr0.8(Fe0.4Co0.6)1.88C0.05合金粉末,用不同的粘结工艺制备粘结样品,用电阻应变片方法测量样品的磁致伸缩性能.结果表明,对不同粘结剂配比的棒状样品,当模压压力为420MPa、粘结荆含量为8％、磁场强度为9 kOe时,样品的磁致伸缩最大(λa=533×10-8);随粘结剂的增加或减少,样品的磁致伸缩均降低;粘结样品的密度随粘结剂含量的增加而减少.     

(Tb1-xRx)0.2Pr0.8(Fe0.4Co0.6)1.88C0.05（R为Ho,Dy）合金结构和磁致伸缩性能的研究

采用电弧熔炼浇铸法和退火处理制备了系列合金A和B:A为(Tb1-xHox)0.2Pr0.8(Fe0.4Co0.6)1.88C0.05(x=0,0.2,0.4,0.6,0.8,1)合金,B为(Tb0.2DyxHo0.8-x)0.2Pr0.8(Fe0.4Co0.6)1.88C0.05(x=0,0.1,0.2,0.3,0.4,0.5)合金。X射线衍射(XRD)分析表明,合金均具有单一的立方Laves相结构。对于合金A,当x=0.8时,磁晶各向异性较小,易磁化方向为<111>方向,合金的磁致伸缩系数达到极大值(504×10-6);对于合金B,当x=0.3时,合金的磁致伸缩系数达到极大值(565.7×10-6)。     

Fe83Ga17合金的磁致伸缩性能和结构分析

采用定向凝固法制备出<110>轴向取向多晶Fe83Ga17合金样品,研究了热处理对合金磁致伸缩性能的影响。发现Fe83Ga17经过淬火处理后,饱和磁致伸缩系数明显增大。在25MPa预压力作用下,饱和磁致伸缩系数λs超过了300×10-6。中子衍射和差热分析表明,Fe83Ga17合金在炉冷过程中存在相结构变化,从而导致合金磁致伸缩系数的改变,淬火处理能够抑制合金中DO3相的形成,从而使Fe83Ga17合金的磁致伸缩应变增大。     

Ce离子的变价行为对Pr_(0.1)Ce_xTb_(0.9-x)Fe_(1.9)化合物性能的影响

用电弧炉熔炼法制备了Pr0.1CexTb0.9-xFe1.9(x=0.2～0.8)化合物。分别采用X射线衍射(XRD)、超导量子干涉磁强计(SQUID)和应变仪分析了化合物Pr0.1CexTb0.9-xFe1.9的相结构、低温磁化曲线和磁致伸缩性能。发现Ce含量x在0.6附近时,Pr0.1CexTb0.9-xFe1.9化合物的晶格常数正向偏离了Vegard定理;低温磁化曲线和磁致伸缩在Ce含量x为0.6时出现反常增加的现象。Pr0.1CexTb0.9-xFe1.9化合物的晶格常数、磁化曲线和磁致伸缩的反常变化归因于Ce离子的价态波动。     

Gd55Fe30P15非晶条带的磁热效应

采用熔体快淬法制备了Gd55Fe30P15合金条带,利用X射线衍射仪(XRD)分析了合金的相结构,通过综合物性测量系统(PPMS)研究了合金的居里温度及磁热效应。研究结果表明,Gd55Fe30P15合金条带是完全的非晶态,其居里温度TC为240K,在居里温度附近发生的磁性转变为二级相变;在5T外场下,最大等温磁熵变为2.73 J/kg.K,低场下,在185～295K宽温区出现一个磁熵变平台;高场下185～270K宽温区出现一个磁熵变平台,从而能够满足磁Ericsson型磁制冷机的要求。     

粘结剂含量对（Pr0.2Tb0．2）（Fe0．4Co0．6）1．88C0．05合金粘结样品磁致伸缩的影响

用HDDR工艺制备Tb0．2Pr0.8（Pr0.2Tb0．2）（Fe0．4Co0．6）1．88C0．05合金粉末,用不同的粘结工艺制备粘结样品,用电阻应变片方法测量样品的磁致伸缩性能。结果表明,对不同粘结剂配比的棒状样品,当模压压力为420MPa、粘结剂含量为8％、磁场强度为9kOe时,样品的磁致伸缩最大（λa=533&#215;10^-6）;随粘结剂的增加或减少,样品的磁致伸缩均降低;粘结样品的密度随粘结剂含量的增加而减少。     

R2Fe17Mx化合物的磁性研究

用自旋极化的ＭＳ－Ｘα方法计算了Ｎｄ２Ｆｅ１７Ｎｘ（ｘ＝０，３）化合物中含哑铃Ｆｅ原子对的Ｆｅ８及含Ｎｄ原子的ＮｄＦｅ６原子簇的电子结构和磁矩。计算结果显示，Ｎｄ２Ｆｅ１７化合物在Ｆｅ（ｃ）和Ｆｅ（ｆ）间的分子轨道中，有三个奇宇称轨道呈现负交换耦合。通过比较α－Ｆｅ的ＭＳ－Ｘａ计算结果能够箐好地说明Ｒ２Ｆｅ１７化合物居里温度较低的原因。在化合物Ｎｄ２Ｆｅ１７Ｎ３中Ｆｅ（ｃ）－Ｆｅ（ｆ）间分子轨道只     

重稀土锰基化合物Gd（Mn,Co）Si的结构与磁性

通过金属钴对锰的替代，考察了Ｇｄ（ＭｎＣｏ）Ｓｉ化合物的晶体结构，居里温度ＴＣ和磁化率随替代量变化的规律，初步探讨了重稀土Ｇｄ原子同过渡金属Ｃｏ，Ｍｎ原子之间以及过渡金属原子与过渡金属原子之间的磁相互作用。     

Electrical and Magnetic Properties of Some Rare Earth Orthoferrites (RFeO3 where R = Y,Ho, Er) Systems

The electrical and magnetic characteristics of some rare earth orthoferrites (RFeO₃, where R = Y, Ho & Er) have been discussed. These two characteristics suggest that such system can be categorized under multiferroic with different Curie and Neel temperature. The electrical characteristics shows relaxation phenomenon with Curie temperature varies with change in frequency. The Curie temperature is in the range of 340–480°C, whereas Neel temperature is about 370°C.     

非计量比Mn_(1.25)Fe_xP_(0.5)Si_(0.5)系列化合物的结构及磁性

用机械合金化和固相烧结的方法制备了Mn_(1.25)Fe_xP_(0.5)Si_(0.5)(x=0.6,0.63,0.65,0.67,0.7,0.75)系列化合物,研究了其结构及磁性。结果表明,该系列化合物的主相均为Fe2P型六角结构,空间群为P-62m;并且随着Fe含量的增加,热滞先减小后增大,居里温度先升高后降低。当Fe的含量为0.65时,热滞最小为1 K,且居里温度最高275 K。当Fe含量为0.63时,化合物的磁熵变最大,在1.5 T的外磁场下的最大磁熵变为10.0 J/kg·K。     

Low temperature cofirable MnZn ferrite for power electronic applications

A new MnZn ferrite tape material for sintering at 900 °C and its performance in power electronic embedded multilayer inductors of several μH inductance are described. The low sintering temperature is achieved by optimizing powder processing and sintering additives. The material is suited for processing within the low temperature cofired ceramics (LTCC) technology and it is particularly compatible with low loss Ag metallization. Although reduced by a factor of two compared to high-temperature sintered material, its relative amplitude permeability of 700 allows for numerous device applications below the Curie temperature of 260 °C. Volumetric losses are not affected by the new material formulation since increased hysteresis losses are compensated by reduced eddy current losses. Power line filters with ceramic integrated inductors and surface mounted capacitors exhibit a current capacity of up to 10 A and a shift in cutoff frequency compatible with the measured B–H curve of the material. By integration of these inductors with conventional dielectric LTCC tapes a strain-induced permeability quenching is revealed and attributed to magnetostriction. Therefore good thermal matching between tape materials is needed, but the effect also permits construction of variometers and pressure sensors without moving mechanical parts.     

TN230B高磁导率NiCuZn铁氧体材料的开发

介绍了一种高磁导率(μi=2300)、高Bs、高居里温度NiCuZn铁氧体TN230B材料的制备方法及生产过程.研究表明,引入适量的CuO可大大改善材料的电磁性能;通过对原材料的选择,严格控制主配方和制备工艺可获得优良的材料性能.     

Characteristics improvement of Li0.058(K0.480Na0.535)0.966(Nb0.9Ta0.1)O3 lead-free piezoelectric ceramics by LiF additions

In this study, a series of Li_0.058(K_0.480Na_0.535)_0.966(Nb_0.90Ta_0.10)O₃ + (x)LiF (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 wt%) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The incorporation of LiF could significantly improve the sintering ability of LKNNT ceramics by reducing the optimal sintering temperature from 1090°C to 1020°C. The crystal phases and micro-structures were analyzed by means of the X-ray diffraction and scanning electronic microscopy, respectively. The impedance analyzer was used to measure the Curie temperature, phase transition point, and electro-mechanical coupling factor. And the d₃₃ meter was used to measure the piezoelectric constants.

From the results, due to the addition of 0.2 wt% LiF, uniform and condensed grains can be obtained and hence the sintering temperature can be lowered down. As the contents of LiF increased, the orthorhombic to tetragonal phase transition points T_O-T were almost no changed, but the Curie temperature T_C decreased from 425°C (x = 0) to 405°C (x = 0.5). And furthermore, the electro-mechanical coupling factor k_p and piezoelectric constant d₃₃ were all decreased with increases of LiF contents. Hence, even though the reducing of little amount of piezoelectric characteristics, the LiF addition can improve the sintering ability of the LKNNT ceramics effectively.