Tb0.3Dy0.7－xPrx(Fe0.9Al0.1)1.95合金的磁致伸缩、自旋重取向和穆斯堡尔谱研究

系统研究了室温下Tb_0.3Dy_0.7-xPr_x(Fe_0.9Al_0.1)_1.95 (x=0，0.1，0.2，0.25，0.3，0.35)合金中稀土元素Pr替代Dy对晶体结构、磁致伸缩、各向异性和自旋重取向的影响. 结果发现，x≤0.1时，Tb_0.3Dy_0.7-xPr_x(Fe_0.9Al_0.1)_1.95完全保持MgCl₂立方Laves相结构，0.1<x≤0.3，有杂相出现并且随Pr替代量逐渐增多；晶格常数a随Pr含量x的增加缓慢增大. 磁致伸缩测量发现，随着替代量x的增多磁致伸缩减小；x>0.2时超磁致伸缩效应消失. 然而，x=0.1时合金的磁致伸缩略大于没有替代的，而且磁致伸缩随磁场更易趋于饱和，说明Pr替代有助于降低磁晶各向异性. 内禀磁致伸缩λ₁₁₁随Pr替代量x的增加接近线性增加. 由相对磁化率随温度的变化关系可以看出，自旋重取向温度随Pr替代量的增多呈先增后降趋势，在x=0.1处出现极大值. 穆斯堡尔效应表明，随Pr含量的增加Tb_0.3Dy_0.7-xPr_x(Fe_0.9Al_0.1)_1.95合金中易磁化轴可能在{110}面上绕主对称轴作微小转动，发生自旋重取向. 与Al元素替代效应相比，Pr替代Dy对自旋重取向的影响相对较小.     

锰位铁掺杂La0.67Sr0.33FexMn1-xO3薄膜的光诱导效应

分别采用溶胶-凝胶法和脉冲激光沉积的方法制备了La_067Sr_033Fe_xMn_1-xO₃(x=0, 005, 010, 015)系列块材和薄膜，研究了Fe部分替代对La_067Sr_033Fe_xMn_1-xO₃薄膜     

层状钙钛矿La1.3Sr1.7Mn2-xCuxO7的磁性及电特性

通过固相反应烧结法成功制备了层状钙钛矿La_1.3Sr_1.7Mn_2-xCu_xO₇多晶，主要研究了其磁电特性.结果表明，样品为Sr₃Ti₂O₇型钙钛矿结构.随着温度的降低，其磁性经历了一个很复杂的转变过程.当x=0时，在T^*=231K出现二维短程铁磁有序，在<     

A novel Dy3+-doped Gd(PO3)3 white-light phosphors under VUV excitation for Hg-free lamps application

Novel Dy³⁺-doped Gd(PO₃)₃ white light phosphors each with an orthorhombic system are successfully synthesized by solid-state reaction. The luminescence properties of white-light Gd_1-x(PO₃)₃:xDy³⁺ (0<x≤ 0.25) under vacuum ultraviolet (VUV) excitation are investigated. The strong absorption at around 147 nm in excitation spectrum energy can be transferred to the energy levels of Dy³⁺ ion from the host absorption. Additionally, the white light phosphor is activated by a single Dy³⁺ ion. Therefore, the luminescence of Gd_1-x(PO₃)₃:xDy (0<x≤ 0.25) under VUV excitation is effective, and it has the promise of being applied to mercury-free lamp.     

Gd,Co共掺杂对BiFeO3陶瓷电输运和铁磁特性的影响

采用快速液相烧结法制备BiFeO₃和Bi_0.95Gd_0.05Fe_1-xCo_xO₃ (x= 0, 0.05, 0.1, 0.15, 0.2)陶瓷样品,研究Gd, Co共掺杂对BiFeO₃微观结构, 介电性能和铁磁性的影响. X射线衍射谱表明:所有样品的主衍射峰与纯相BiFeO₃相符合且 具有良好的晶体结构,随着Co³⁺掺杂量x的增大, Bi_0.95Gd_0.05Fe_1-xCo_xO₃样品的主衍射峰(104)与(110)逐渐相互重叠, 当x大于0.1时, 样品呈现正方晶系结构; J-V特性显示Gd³⁺, Co³⁺共掺杂有效地降低BiFeO₃陶瓷的漏导电流,其降低幅度为1-2个数量级; 当f=10³ Hz时, Bi_0.95Gd_0.05Fe_0.8Co_0.2O₃的介电常数是BiFeO₃的6倍, 而Bi_0.95Gd_0.05Fe_0.95Co_0.05O₃和 Bi_0.95Gd_0.05Fe_0.85Co_0.15O₃样品的介电损耗最小,均为0.01.室温下, Bi_0.95Gd_0.05Fe_1-xCo_xO₃样品磁性与BiFeO₃相比显著增强. 在磁场为30 kOe的作用下,Bi_0.95Gd_0.05Fe_1-xCo_xO₃ (x= 0, 0.05, 0.1, 0.15, 0.2)的剩余磁化强度M_r分别是BiFeO₃的34, 60, 105, 103, 180倍.样品磁性增强的主要原因是Gd, Co掺杂使BiFeO₃的晶格结构发生变化导致BiFeO₃自身储存的磁性能被释放, Gd³⁺的4f电子与Fe³⁺或Co³⁺的3d电子自旋相互作用及样品中存在局域的 Fe-O-Co磁耦合三者共同作用的结果.     

Mn4+掺杂对BiFeO3陶瓷微观结构和电学性能的影响研究

利用传统的固相反应法制备了BiFe_1-xMn_xO₃ (x= 0-0.20)陶瓷样品, 研究了不同Mn⁴⁺掺杂量对BiFeO₃陶瓷密度、物相结构、显微形貌、 介电性能和铁电性能的影响.实验结果表明:所制备的BiFe_1-xMn_xO₃ 陶瓷样品的钙钛矿主相均已形成,具有良好的晶体结构, 且在掺杂量x=0.05附近开始出现结构相变.随着Mn⁴⁺添加量的增加, 体系的相结构有从菱方钙钛矿向斜方转变的趋势,且样品电容率大幅度增大, 而介电损耗也略有增加;在测试频率为10⁴ Hz条件下, BiFe_0.85Mn_0.15O₃ (ε_r=1065)的 ε_r是纯BiFeO₃ (ε_r=50.6)的22倍; 掺杂后样品的铁电极化性能均有不同程度的提高,可能是由于Mn⁴⁺稳定性优于 Fe³⁺,高价位Mn⁴⁺进行B位替代改性BiFeO₃陶瓷, 能减少Bi³⁺挥发,抑制Fe³⁺价态波动,从而降低氧空位浓度,减小样品的电导和漏电流.     

窄带隙KNb1-xFexO3-δ的室温铁磁性

We have investigated the structure, optical and magnetic properties of ferroelectric KNb_1-xFexO_3-δ (X=0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25) synthesized by a traditional solid-state reaction method. According to the X-ray diffraction and the results of Rietveld refinement, all the samples maintain orthorhombic distorted perovskite structures with Amm2 space group without any secondary phase, suggesting the well incorporation of Fe ions into the KNbO₃ matrix. With the increase of Fe concentration, the band gap of each sample is decreased gradually, which is much smaller than the 3.18 eV band gap of pure KNbO₃. Through X-ray photoelectron spectrum analysis, the increased density of oxygen vacancy and Fe ions may be responsible for the observed decrease in band gap. Compared with the pure KNbO₃, Fe doped samples exhibit room-temperature weak ferromagnetism. The ferromagnetism in KNb_1-xFexO_3-δ with low-concentration dopants (X=0.01-0.10) can be attributed to the bound magnetic polaron mediated exchange. The enhancement of magnetism for the high-concentration (X=0.10-0.20) doped samples may arise from the further increase of magnetic Fe ions.     

Nd1-xSrxMnO3中掺杂浓度对电脉冲诱导电阻转变效应的影响

采用两线测量模式对固相烧结方法制备的Nd_1-xA_xMnO₃ (A= Ba, Ca, Sr,x= 0-0.9) 陶瓷样品电脉冲诱导电阻转变(EPIR)效应和I-V特性进行了测量. 结果表明, 与Nd_0.7Sr_0.3MnO₃一样, 相同浓度掺杂的Nd_0.7Ba_0.3MnO₃和Nd_0.7Ca_0.3MnO₃ 样品也能诱发稳定的室温EPIR效应. 进一步对Nd_1-xSr_xMnO₃系列样品的EPIR研究表明, 这种界面相关的EPIR效应与样品中电子或空穴掺杂浓度密切相关, 在半掺杂 (x= 0.5)附近, 样品与电极接触界面能诱发稳定的EPIR效应. 然而, 随掺杂浓度的进一步增大或降低, EPIR效应逐渐出现减弱、不明显到完全消失的过程. 产生这种现象的原因可能与锰氧化物中由于掺杂浓度差异所导致的界面缺陷在不同极性脉冲激励下重新分布而产生的内电场强弱有关.     

镨掺杂对无钴钙钛矿型氧化物BaFeO3-δ电导率和透氧性能的影响

Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes,cubic phase structure is the most favorable for oxygen permeation.In order to stabilize the cubic perovskite structure of BaFeO_3-δ material at room temperature,iron was partially substituted by praseodymium.BaFe_1-yPr_yO_3-δ powders were synthesized by a solid state reaction method,and sintered samples were prepared from the synthesized BaFe_1-yPr_yO_3-δ powders.X-ray diffraction results reveal that the BaFe_1-yPr_yO_3-δ samples remain cubic structure at praseodymium substitution amount of y=0.05,0.075,0.1.Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe_1-yPr_yO_3-δ increase monotonically with the increase of the praseodymium doping amount,praseodymium doping promotes the grain size growth.Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe_1-yPr_yO_3-δ and BaFe_0.9Pr_0.1O_3-δ composition has an electrical conductivity of 6.5 S/cm and an oxygen permeation of 1.112 mL/(cm²·min) at 900 ℃,respectively.High temperature XRD investigation shows that the crystal structure of BaFe_0.975Pr_0.025O_3-δ membrane completely transform to cubic phase at 700 ℃.The present test results have shown that partially substitution of Fe by praseodymium in BaFeO₃ can stabilize the cubic structure and improve the properties.     

Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.     

过渡族元素掺杂BaTiO3-Tb1-xDyxFe2-y层状复合材料中的磁电效应

用溶胶-凝胶法制备1.0%mol Mn,Cr,Co掺杂 BaTiO₃(BTO)粉体,在1350℃下烧结成多晶陶瓷样品.X射线衍射和差示扫描量热分析表明,室温下掺杂BaTiO₃具有四方钙钛矿结构;居里点和相变潜热随Cr,Mn,Co掺杂逐渐降低.将掺杂BaTiO₃与Tb_1-xDy_xFe_2-y(TDF)胶合制成双层磁电复合材料,并研究了Cr:BTO-TDF,Mn∶BTO-TDF,Co:BTO-TDF层状复合材料中的磁电效应.实验表明,在340×80 A·m^-1偏置磁场下, Cr:BTO-TDF的横向磁电电压系数达到最大值586 mV·cm^-1·(80 A·m^-1)^-1.在400×80 A·m^-1偏置磁场下,Mn∶BTO-TDF和Co:BTO-TDF的横向磁电电压系数的最大值分别为480 mV·cm^-1·(80 A·m^-1)^-1和445mV·cm^-1·(80 A·m^-1)^-1.研究表明掺杂BaTiO₃-TDF层状复合材料中具有较强的磁电耦合.作为无铅压电材料,掺杂BaTiO₃制备的磁电效应器件颇具应用前景. 关键词： 磁电效应 双层复合材料 3')" href="#">掺杂BaTiO₃ 1-xDy_xFe_2-y')" href="#">Tb_1-xDy_xFe_2-y     

磁电双层膜层间耦合的弹性力学研究

基于磁致伸缩相与压电相的本构方程,应用弹性力学模型,简要介绍了如何推导自由状态的磁电双层膜纵向、横向磁电(ME)电压系数. 并采用相应的材料参数计算了La_07Sr_03MnO₃-Pb(Zr,Ti)O₃ (LSMO-PZT),Tb_1-xDy_xFe_2-y(TDF)-PZT双层膜中的磁电电压系数,具体分析了其与压电相 关键词： 磁电效应 双层膜 TDF LSMO PZT     

单磁场驱动的Tb1-xDyxFe2-y/Pb(Zr,Ti)O3三层膜磁电效应

研究了Tb_1-xDy_xFe_2－y (TDF)与锆钛酸铅(PZT)三层膜样品的制备和在单一直流磁场驱动下的磁电(ME)效应. 在该系列三层膜样品中测量到了巨大的ME耦合效应. 所得实验结果与同种样品在两磁场驱动下的ME效应完全不同. 这可能预示了某些新的物理内容. 该技术可简化ME效应在某些实际应用中的复杂度. 关键词： 1-xDy_xFe_2－y')" href="#">Tb_1-xDy_xFe_2－y PZT 单磁场 ME效应     

层状磁电复合材料谐振频率下的巨磁电容效应

对三明治复合结构Tb_xDy_1-xFe_2-y/Pb(Zr, Ti)O₃/Tb_xDy_1-xFe_2-y的电容与频率及磁场的函数关系进行了实验和理论研究. 实验发现,该复合材料样品的电容随频率的增加而出现多个谐振峰,并且其谐振点随磁场的增加而发生频移. 在谐振点附近,观察到样品的阻抗随磁场的增加由容抗性转变为感抗性,从而同时观察到巨大的正磁电容效应和负磁电容效应. 由复合材料的弹性力学本构方程出发,对该类样品的电容随频率及磁场的变化进行了理论模拟. 结果显示,模拟曲线与实验结果符合得很好. 理论表明该磁致伸缩/压电复合材料的磁电容效应源于磁场诱变的铁磁相柔顺系数. 关键词： 层状复合材料 界面弹性耦合 磁电容效应     

Fe掺杂量对双层复合结构BaTi1-zFezO3+δ-Tb1-xDyxFe2-y中磁电耦合的影响

采用溶胶凝胶方法制备了Fe掺杂钛酸钡多晶系列陶瓷BaTi_1-zFe_zO_3+δ(0.005≤z≤0.02) (BTFO).X射线衍射实验显示,所制备的BTFO的结构仍然为四方相钙钛矿.差热分析表明,该BTFO样品的铁电-顺电转变温度及相变潜热随掺杂量z的增加而下降.将该BTFO极化后与Tb_1-xDy_xF 关键词： 磁电耦合 掺杂效应 掺杂钛酸钡     

Influence of the concentration in Fe-doped BaTiO3 on magnetoelectric couping of layered composites BaTi1−xFexO3–Tb1−yDyyFe2−z

Perovskites BaTi_1−xFe_xO₃ has been synthesized with the concentration x ranging from 0.01 to 0.02. Their transformation point of ferroelectric to paraelectric and the corresponding latent heat of the phase transformation were observed to decrease with increasing the doping level of Fe³⁺. Bonded layered composites BaTi_1−xFe_xO₃–Tb_1−yDy_yFe_2−z have been fabricated and their magnetoelectric effect has been investigated. The sample containing a layer of perovskite BaTi_0.985Fe_0.015O₃ was found to show the maximum transverse ME voltage coefficient, which is about 1422 mV Oe⁻¹ cm⁻¹ under a magnetic field of 1580 Oe, in these bilayers. Analysis shows that the Fe-doped BaTiO₃ with doping level at about 1.5% should have largest piezoelectric coefficient in these ceramics BaTi_1−xFe_xO₃.     

Structure and magnetic properties of melt-spun Tb0.27Dy0.73Fex ribbons

The structure and magnetic properties of the melt-spun ribbons of Tb_0.27Dy_0.73Fe_x alloy are investigated as a function of various wheel speeds during melt-quenching using a single-roll technique. It is found that Tb_0.27Dy_0.73Fe_x alloy is difficult to be fabricated as amorphous state by using the melt-quenching method. X-ray diffractions show that all these ribbons for x=1.7−2.0 are the MgCu₂-type phase at the wheel speed of 45 m s⁻¹. For Tb_0.27Dy_0.73Fe_x alloy, the high wheel speed is beneficial to eliminate the RFe₃ phase and form the perfect MgCu₂-type phase. Compared with the bulk of Tb_0.27Dy_0.73Fe_1.95, these ribbons exhibit higher intrinsic coercivity value and their saturation magnetizations increase as well. The magnetostriction of Tb_0.27Dy_0.73Fe_1.95 composite with 4% epoxy resin is 640×10⁻⁶ at 900 kA m⁻¹.     

Tb$lt;sub$gt;0.3$lt;/sub$gt;Dy$lt;sub$gt;0.6$lt;/sub$gt;Pr$lt;sub$gt;0.1$lt;/sub$gt;(Fe$lt;sub$gt;1-$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;Al$lt;sub$gt;$lt;i$gt;x$lt;/i$gt;$lt;/sub$gt;)$lt;sub$gt;1.95$lt;/sub$gt;合金的磁性、磁致伸缩和穆斯堡尔谱研究

系统研究了室温下Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95 （x=0.05,0.1,0.15,0.2,0.25,0.3）合金中元素Al替代Fe对结构、磁性、磁致伸缩性能和自旋重取向的影响.测量结果发现,x<0.2时Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95合金基本上是纯的单相,x=0.2时出现其他杂相,杂相随Al替代量的增加不断增多.随Al替代量x的增加,点阵常数a接近于线性增大,Curie温度T_C逐渐下降,而矫顽力H_c急剧下降.振动样品磁强计（VSM）测量发现,磁化强度M随Al替代量x的变化较为复杂.VSM计和磁致伸缩效应测量共同表明,少量Al的替代有利于降低磁晶各向异性,而且随着Al替代量x的增多磁致伸缩系数快速减小,x>0.15时巨磁致伸缩效应消失.穆斯堡尔效应研究发现,随Al含量的增加Tb_0.3Dy_0.6Pr_0.1（Fe_1-xAl_x）_1.95合金中易磁化轴可能在{110}面逐渐偏离了立方晶体的主对称轴,发生自旋重取向,从而引起合金宏观磁性、磁致伸缩性能的变化. 关键词： 磁致伸缩 立方Laves相 自旋重取向 穆斯堡尔谱     

Structure and magnetostriction of RFex (1.6 x 2.0) and R(Fe1−yTiy)1.8 (y 0.2) alloys (R=Dy0.65Tb0.25Pr0.1)

Structure, Curie temperature and magnetostriction of RFe_x (1.6 x 2.0) and R(Fe_1−yTi_y)_1.8 (y 0.2) alloys (R=Dy_0.65Tb_0.25Pr_0.1) have been investigated using optical microscopy, X-ray diffraction, AC initial susceptibility and standard strain gauge techniques. The homogenized RFe_x alloys are found to be essentially single phase in the range of 1.8 x 1.85. The second phase is a rare-earth-rich phase when x 1.8, and (Dy, Tb, Pr)Fe₃ phase when x 1.85. X-ray diffraction indicates that the R(Fe_1−yTi_y)_1.8 alloys contain a small amount of Fe₂Ti phase when y 0.05, which increases with the increment of Ti content. The Curie temperature of R(Fe₁−_yTi_y)_1.8 alloys slightly enhances with increasing Ti concentration when y 0.05, then remains almost unchanged in the range of 0.05 y 0.20. The magnetostriction of RFe_x alloys is improved when x 1.80 and reduced by increasing Fe content when x 1.85. The magnetostriction of R(Fe_1−yTi_y)_1.8 alloys is lowered by increasing Ti content.