铜模吸铸法制备Fe-Nd-Al-B-Dy合金的结构和磁性能

为了进一步改善Fe-Nd-Al-B非晶合金的非晶形成能力和磁性能,研究添加Dy元素对此体系合金的显微结构、磁性能以及晶化行为的影响.利用铜模吸铸法制备厚度为1mm的片状(Fe0.51Nd0.35Al0.10b0.40)100-xDyX(x=0,1,3,6)合金.采用示差扫描量热法(DSC),振动样品磁强计(VSM)和X射线衍射仪(XRD)研究Dy对该系列合金非晶形成能力、磁性能和晶化行为的影响.结果表明,添加少量Dy元素使得合金Fe-Nd-Al-B-Dy的磁性能各项指标大幅度提高,得到较好的硬磁性.然而,当进一步提高Dy含量到6%时,合金呈现顺磁性.Fe-Nd-Al-B-Dy系合金晶化后,磁性能会发生很大转变,其中具有较好硬磁性的(Fe0.51Nd0.35Al0.10B0.04)99Dy1合金在完全晶化后呈现为顺磁性.     

金属原子(Li/K)掺杂对NaMgH3体系放氢性能影响的理论研究

通过密度泛函理论研究了NaMgH_3和M(Li/K)替代部分Na体系的电子结构和放氢热力学性质。计算了掺杂体系沿着4条可能的反应路径的反应焓,表明掺杂体系以反应M_xNa_(1-x)MgH_3→xMH+(1–x)NaH+Mg+H_2放氢的可能性最大。Li替代部分Na后降低了体系的反应焓,改善了体系的放氢热力学性能;而K掺杂体系的反应焓变化不明显。通过对电子态密度和键布局的分析表明:Li的掺入降低了离子对价带的贡献,同时减弱了Li与H之间的相互作用,这有利于体系放氢。计算Li在不同掺杂浓度下的反应焓,表明随着Li掺杂量的增加,掺杂体系放氢热力学性能逐步改善,但Li的掺杂量不能超过50.00%。     

稀土La^3＋离子取代对M型锶铁氧体的结构和磁性的影响

采用陶瓷工艺，制备了Sr1-xLaxFe12O19M型锶铁氧体，系统地研究了稀土La^3 取代Sr^2 对M型六角铁氧体的结构和磁性的影响，La^3 离子取代部分的Sr^2 离子能明显改善M型铁氧体的内禀磁性。     

溶胶凝胶法合成Dy~(3+)离子掺杂的二氧化锆及其发光特性(英文)

采用溶胶凝胶法合成 Dy3+离子掺杂的单斜与正交的二氧化锆晶体,研究了结晶温度、时间、Dy3+离子浓度对氧化锆结构的影响。比较研究了 Dy3+离子在不同结构二氧化锆中的光谱特性,从结果看出,Dy3+离子可作为荧光探针反映二氧化锆的晶体结构。     

简讯

稀土永磁材料TbxDy1-xFe1.95合金相结构和磁性能印度国防冶金研究实验室Mithun Palit等人研究了真空感应炉制造的TbxDy1-xFe1.95合金（x=0～1）。研究Tb/Dy比值对结构和磁性影响。研究结果表明：主相（Tb,Dy）Fe2和副相（Tb,Dy）Fe3、（Tb,Dy）固溶体在3个合金中是共存的。     

添加Dy对纳米晶复合Nd8.5Fe77Ga0.6Co5Zr2.7B6.2永磁材料磁性能和温度系数的影响

采用快淬后真空晶化退火工艺制备了成分为Nd8.5-xDyxFe77Ga0.6Co5Zr2.7B6.2(x=0,0.5,1.0)的纳米晶复合永磁粘结磁体,研究其磁性能和温度系数的变化。结果表明,添加Dy元素能有效提高磁体的内禀矫顽力,但使其剩磁和较大磁能积略有下降。Dy含量为0.5at%时,制得的粘结磁体具有较佳磁性能:Br=0.728T,jHc=656.3kA/m,(BH)max=76.2kJ/m3。随着Dy元素的添加,合金的剩磁温度系数α逐渐降低,当Dy=1at%时,在20℃~150℃温度区间内平均剩磁温度系数α=-0.12%/℃。随着Dy元素的添加,合金的内禀矫顽力温度系数β呈先下降后上升的趋势。在Dy=0.5at%时,具有较低的β值,在20℃~150℃温度区间内平均内禀矫顽力温度系数β=-0.34%/℃。     

1-乙基-3-甲基-咪唑四氟硼酸盐离子液体中镝电沉积行为

研究室温下Pt电极上Dy3+离子在1-乙基-3-甲基-咪唑四氟硼酸盐(EMIMBF4)离子液体中的电化学行为。循环伏安法结合计时电流法和计时电位法研究结果表明,Dy3+离子的电化学还原是不可逆过程,还原为一步完成,即Dy3++3e-→Dy。计时电流法结合恒电位电解研究表明,Dy3+离子的还原过程受扩散控制。测得浓度0.01mol/L的Dy3+离子在0.1mol/LLiCl-EMIMBF4离子液体中的传递系数、扩散系数分别为0.176和(4.87-5.04)×10-10cm2/s。SEM和XRD分析表明,金属镝颗粒直径为几百纳米。     

氢处理时Er2Fe14B化合物磁性变化基本规律

俄罗斯BafiooB冶金与材料研究院M．A．1-IeeBnH等人综合研究了金属间化合物ErzFe14B及其氢化物的结构和磁性,表明结构和磁性对氢含量很敏感,     

DyF3涂敷量对NdFeB磁体热扩渗过程、磁性能的影响及其机制

涂敷法作为重稀土热扩渗技术的一种,具有低成本、操作简单等优点,现已成为工业化应用的主流技术.目前为了获得好的热扩渗效果,需要涂覆大量的DyF3粉,这造成不必要的浪费.针对该问题,利用自主研发的DyF3新型涂料烧结NdFeB进行热扩渗处理.研究了不同DyF3涂敷量热扩渗磁体的性能、微观组织结构和Dy元素分布.结果 表明,Dy浓度差是热扩渗的驱动力,因此涂敷量对样品矫顽力提升有重要影响.涂敷量较少时,Dy元素热扩渗不充分,导致矫顽力的提升有限;随着涂覆量增加,Dy元素的扩渗充分,在晶界中均匀分布,此时磁体具有最佳的综合磁性能;继续增加涂覆量,Dy和涂液中C、F等元素开始进入主相晶粒,造成磁性能的恶化,磁性能反而下降.因此重稀土涂覆量应在适当范围内,过多和过少都会造成热扩渗效果不好.最佳DyF3涂敷量为0.81％(质量分数),经过热扩渗后,矫顽力由14.60 kOe提升到19.78 kOe,剩磁的下降很小,磁体达到最佳的综合性能.     

制取低温度系数Nd—Fe—B磁体的混合合金法工艺

将组成分别为Nd3.5Dy30.0Fe65.5Nb0.4B1.1和Nd33.5Fe30.5Co35.0Nb0.4B1.1（质量百分数）的铸态Nd-Fe-B合金按比例进行混合，使合金中的（Dy Co)总量基本保持不变，让Dy和Co的相对含量发生变化，采用粉末冶金工艺生产Nd-Fe-B磁体。结果发现：磁体的Br随着含Co合金比例的增加线性增大，iHc随着含Co合金比例的增加线性减小，但磁体的磁通可逆温度系数却只在较小的范围内变化。这说明当（Dy Co)含量保持在一定范围内时，既可以通过增加Dy含量降低磁体的温度系数也可以通过增加Co含量降低磁体的温度系数。在此研究的基础上，通过调整初始合金的成分和工艺,制成了磁性能为18MGOe/23kOe-25MGO3/15kOe、磁通可逆温度系数为－0．018％／℃-0.026%/℃的高稳定性，低温度系数Nd-Fe-B系列磁体。     

Effect of Dy doping on magnetism of La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>CoO<Subscript>3</Subscript> system

The effect of Dy doping on magnetism of La0. 7Sr0. 3CoO3 system was studied through the measurements of M-T curves and M-H curves. The results show that with Dy content increasing, Tc decreases, M weakens, the coercive force strengthens, and the samples exhibit the abnormal phenomenon that M increases continuously with T decreasing in low temperature range. Research indicates that the variation of magnetism in the system comes from the changes of lattice parameters and magnetic environment caused by Dy doping and from the spin-state transition of Co ions induced by Dy ions.     

Dy~(3+)掺杂BiFeO_3薄膜的晶格转变和磁性能研究(英文)

以硝酸铋、硝酸铁以及硝酸镝等无机硝酸盐为原料通过化学液相法在Pt(111)/Ti/SiO_2/Si上制备了Dy~(3+)掺杂的BiFeO_3薄膜,研究了Dy~(3+)掺杂量的变化对Bi_(1-x)Dy_xFeO_3薄膜的晶体结构和磁性的影响.Dy~(3+)掺杂量不高于10%的Bi_(1-x)Dy_xFeO_3薄膜可以得到与纯BiFeO_3相同的晶体结构.随着Dy3+掺杂量的进一步增大,Bi_(1-x)Dy_xFeO_3薄膜的晶体结构发生变化,晶格从菱心结构转变为单斜或四方结构.磁性测试显示:随着Dy~(3+)掺杂量的增加Bi_(1-x)Dy_xFeO_3薄膜的磁性增强,同时从无饱和磁化强度和零磁滞的S型磁化曲线的形状判断,薄膜由于铁磁反铁磁转变时两磁性相竞争表现出自旋玻璃态的特征.     

Influence of Gd Doping on Magnetic Behavior in La0.67Sr0.33CoO3, La0.67Sr0.33MnO3

研究了La0.67-xGdxSr0.33CoO3、La0.67-xGdxSr0.33MnO3 (x=0.00, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.67)体系的M-T曲线、M-H曲线。结果表明:随Gd掺杂浓度增高,La0.67-xGdxSr0.33CoO3体系的磁结构表现为团簇玻璃态,x>0.10样品的M-T曲线出现了低温区M值急剧上升的奇特现象;La0.67-xGdxSr0.33MnO3体系的磁结构从长程铁磁有序向团簇玻璃态、反铁磁状态转变,x≥0.50样品的M-T曲线在低温区急剧下降。两种体系呈现的不同现象,来源于Gd与Co、Mn不同的耦合作用和Co的自旋态的转变。     

Microstructure and microwave electromagnetic properties of Dy~（3＋）-doped W-type hexaferrites

Ba 1 x Dy x Co 2 Fe 16 O 27 (x = 0.00, 0.05, 0.10, 0.15, and 0.20) was prepared by the solid-state method. The phase structure was studied using powder X-ray diffraction (XRD), the electromagnetic properties were measured, and the reflection loss of Dy 3+ -doped ferrite material was calculated using electromagnetic parameters by the transmission line theory. All XRD patterns showed the single phase of the magnetoplumbite barium ferrite without other intermediate phase when x ≤ 0.15. The values of ε′ and ε″ increased slightly with Dy 3+ ions doping. The values of μ″ and μ′ were improved with Dy 3+ doping, exhibiting excellent microwave magnetic performance. The reasons have also been discussed using the electromagnetic theory. Dy substitution could increase microwave-absorbing performance and broaden frequency band (reflection loss (RL) < -10 dB), and the absorbing peak shifted to high-frequency position. When x = 0.2, ferrite layer exhibited the most excellent microwave-absorbing performance at a thin matching thickness of 1.5 mm. The peak value of RL was around -15 dB, and the frequency band (RL < -10 dB) was about 7 GHz (from 8 to 15 GHz).     

Electro-catalytic degradation properties of Ti/SnO<Subscript>2</Subscript>–Sb electrodes doped with different rare earths

Ti/SnO₂–Sb electrode has a good effect on the removal of organic pollutants. But its short service life limits its large-scale application in industry. Electro-catalytic degradation performances and service life of the electrode can be significantly improved by doping rare earth (RE) ions into the oxide coating of Ti/SnO₂–Sb electrode. Ti/SnO₂–Sb electrodes doped with different RE elements (Ce, Dy, La, and Eu) were prepared by the thermal decomposition method at 550 °C. Electro-catalytic degradation performances of electrodes doped with different RE elements were evaluated by linear sweep voltammetry (LSV) and Tafel curves. During the electrolysis, the conversion of p-nitrophenol was performed with these electrodes as anodes under galvanostatic control. The structures and morphologies of the surface coating of the electrodes were characterized by scanning electron microscope (SEM). The results demonstrate that the electro-catalytic degradation performances of Ti/SnO₂–Sb electrodes are improved to different levels by doping different RE ions. Improved Ti/SnO₂–Sb electrodes by the introduction of different RE have higher oxygen evolution potential, better electro-catalysis ability, better coverage, and longer electrode life.     

Research on charge ordering and magnetic properties in La0.3Ca0.7Mn1-xWxO3 system

The perovskite manganite sample La0.3Ca0.7Mn1-xWxO3 （x = 0.08, 0.12） was prepared by the solid-state reaction method. The effect of W doping on the Mn site to La0.3Ca0.7MnO3 charge ordering phase and the changing process of magnetic properties were studied through the measurement of the M-T curve, M-H curves, and ESR curves of the sample. The results showed that when x = 0.08, the charge ordering （CO） phase exists in the system, the transition temperature Tco= 275 K, and the system exhibits PM when T 〉 275 K. The system transforms from spin-disordering paramagnetism to spin-ordering antiferromagnetism in the charge ordering state with the temperature decreasing from 275 K to 230 K. The long-range antiferromagnetism forms and AFM/CO states coexist between 230 K and 5 K. There is a little ferromagnetic component in the AFM/CO background in a low temperature range. When x = 0.12, the CO phase in the system has almost melted completely. There is a little remnant of the CO phase below 150 K. The system exhibits paramagnetism when T 〉 150 K and transforms from paramagnetism to ferromagnetism when T〈 150 K.     

Study on magnetism of Pr0.45（Ca1-xSrx）0.55MnO3 samples

The polycrystalline samples of Pr_0.45(Ca_1−x Sr _x )_0.55MnO₃ (x = 0.0, 0.2, 0.4, 0.6) were prepared by solid-state reaction. Influence of Sr²⁺ substitution for Ca²⁺ at A site on magnetism was studied through the measurements of X-ray diffraction (XRD) spectrum, the magnetization-temperature (M-T) curves and electron spin resonance (ESR) curves. The results show that the magnetism strengthens and charge ordering weakens gradually with the increase of Sr²⁺ substitution amount, respectively. The transition of paramagnetism(PM)-antiferromagnetism(AFM) occurs below the transition temperature of charge ordering (T _CO), and there is little ferromagnetic phase in the antiferromagnetic background at the lower temperature, which results in complex magnetic phases of the samples. Ferromagnetic clusters appear and grow larger with the increase of substitution amount. In addition, the reentrant spin-glass behavior appears at about 41 K. The magnetism phenomenon of the samples is mainly due to the competition between double exchange and Jahn-Teller coupling. The Jahn-Teller coupling becomes weak, and the double exchange wins the advantage in the competition with the increase of substitution amount, which leads to the magnetism variation of the system.     

Influence of La^3＋ and Dy^3＋ on the properties of the long afterglow phosphor CaAl2O4： Eu^2＋, Nd^3＋

The long afterglow phosphor CaAl2O4:Eu2+,Nd3+ was prepared by the high temperature solid-state reaction method,and the influence of La3+ and Dy3+ on the properties of the long afterglow phosphor was studied by X-ray diffraction (XRD),photoluminescence (PL),and thermoluminescence (TL),The XRD pattern shows the host phase of CaAl2O4 is produced and no impurity phase appears.The peak wavelength of the phosphor does not vary with La3+ and Dy3+ doping.It implies that the crystal field,which affects the 5d electron states of Eu2+ is not changed dramatically after doping of La3+ and Dy3+.The TL spectra indicate that the phosphor doped with La3+ or Dy3+ produces different depths of trap energy level.In the mechanism of long afterglow luminescence,it is considered that La3+ or Dy3+ works as trap energy level.The decay time lies on the number of electrons in the trap energy level and the rate of the electrons returning to the excitation level.     

Relating atomic local structures and Curie temperature of NdFeB permanent magnets:an X-ray absorption spectroscopic study

Relationship between atomic local structures and Curie temperature of NdFeB permanent magnets was investigated semi-quantitatively using synchrotron radiation technique. Fe K-edge X-ray absorption spectroscopy(XAS) was employed to study the local structure of Fe atoms for samples before and after doping Dy, Tb or Gd. It is found that the bond lengths and coordination numbers are changed. Thus, the exchange interaction between Fe atoms increases with Dy, Tb or Gd doping, resulting in the improvement of Curie temperature of NdFeB permanent magnets. The doping effect is proven by experimental measurement of the magnetic properties. Microstructural characterization using scanning electron microscopy(SEM) was also used to further analyze the effect of different rare earth elements doping on Curie temperature of NdFeB permanent magnets.     

Luminescent properties of CaMgSi2O6 and Ca2MgSi2O7 phosphors activated by Eu, Dyand Nd

Long lasting alkaline earth silicates, CaMgSi₂O₆:Eu,Dy,Nd, Ca₂MgSi₂O₇:Eu,Dy,Nd and Ca₂MgSi₂O₇:Eu,Dy, were prepared under a reducing atmosphere by a solid-state reaction. The obtained phosphors were characterized by means of X-ray diffraction (XRD) and their photoluminescence spectrum (PLS). The Ca₂MgSi₂O₇:Eu,Dy,Nd phosphor showed a two-peak emission at 447 and 516 nm, while the CaMgSi₂O₆:Eu,Dy,Nd phosphor generated only one peak emission at 447 nm. This phenomenon is due to the different lattice sites occupied by Eu²⁺ in the Ca₂MgSi₂O₇ and CaMgSi₂O₆ lattices. The electron affinity (ea) values for Eu²⁺ in [EuO₆] and [EuO₈] were calculated to be 4.2 and 1.9 eV, respectively. The Nd co-doped phosphor revealed a better afterglow characteristic, indicating that a deeper trap center was formed in the phosphor by the doping of trivalent Nd ions.