Ni0.5Zn0.5Fe2O4粉末化学镀铜前后的电磁性能

本文用溶胶-凝胶自燃烧法制备了Ni0.5Zn0.5Fe2O4粉末颗粒,以甲醛为还原剂在Ni0.5Zn05Fe2O4颗粒表面进行了化学镀铜,制备了Cu/Ni0.5Zn0.5Fe2O4复合粉体.用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)对镀铜前的Ni0.5Zn0.5Fe2O4颗粒以及镀铜后的复合纳米颗粒进行了表征.对镀铜前的Ni0.5Zn0.5Fe2O4粉体和不同镀铜量的Cu/Ni0.5Zn0.5Fe2O4复合粉体进行了电磁性能的研究,结果表明镀铜后镍锌铁氧体的吸波性能明显提高,增重量为65%的Cu/Ni0.5Zn0.5Fe2O4复合粉体在频率为11GHz处反射率可达-12dB左右.     

基于工业级原料FeMoPC块体非晶态合金的制备

通过Fluxing提纯技术和J-quenching快速凝固技术相结合的方法,成功制备了基于工业级原料的Fe80-xMoxP13C7(x=0,4,8,12)块体非晶态合金。结果表明,少量的Mo置换Fe能够提高Fe80P13C7合金的玻璃化形成能力,当Mo的替换量为8%时,合金的玻璃化形成临界尺寸达到4mm,然而Mo含量的进一步增加则使合金的玻璃化形成能力降低。随着Mo含量的增加,FeMoPC块体非晶态合金的玻璃转变温度(T_g)和起始晶化温度(T_x)单调增加,而冷液相区宽度(ΔT_x=T_x-T_g)先增大后减小。压缩测试结果显示,随着Mo含量的增加,FeMoPC块体非晶态合金的压缩断裂强度(σ_f)和塑性应变(ε_p)都先增大后减小,当Mo含量为8%时,合金的σ_f和ε_p都分别达到了最大值3.6GPa和4.6%。磁性测试结果表明,随着Mo含量从0%增加到12%,FeMoPC块体非晶态合金的饱和磁化强度从1.42T降为0.33T,这可能是由于Mo与Fe原子间反铁磁耦合造成的。     

(Fe0.5 Co0.5)73.5 Cu1 Mo3 Si13.5 B9合金高温磁性的研究

研究了460～580℃等温退火(30min)后纳米晶(Fe0.5 Co0.5)73.5 Cu1Mo3Si13.5B9合金高温软磁性能.结果表明,在Fe73.5Cu1Mo3Si13.5B9纳米晶合金中用Co取代部分Fe仍可形成双相纳米晶结构,并且可显著提高合金的高温特性.与Fe73.5Cu1Mo3Si13.5B9纳米晶软磁合金相比,其室温μi略有下降,但表征高温磁稳定性的居里温度明显提高,同时磁导率在高温下衰减变缓,从而拓宽了纳米晶软磁材料的高温使用范围.文中初步探讨了用Co取代部分Fe后使高温特性得到改善的机理.     

钴基非晶软磁合金粉末的纳米晶化及其磁性能研究

采用球磨法制备了钴基非晶软磁合金粉末.X射线衍射(XRD)分析结果表明在形成了非晶态合金之前有CoZr2金属间化合物相析出,透射电子显微镜(TEM)分析发现在20h时获得了非晶态的Co80Zr20合金.采用示差热分析(DTA)研究了Co80Zr20非晶粉末的热稳定性和非晶形成能力,结果表明该体系具有很大的非晶形成能力和较强的热稳定性.对Co80Zr20非晶软磁合金粉末在833K～893K退火1h,在振动样品磁强计(VSM)上测量了其磁滞回线,结果表明Co80Zr20合金具有优良的综合软磁性能.     

合金元素对非晶形成能力及力学性能的影响

采用铜模吸铸法制备了直径为(Φ)4mm的合金Fe55Ni2Cr12Mo10B6C13Y2,Fe55Cu2Cr12Mo10B6C13Y2和Fe55Nb2Cr12Mo10B6C13Y2.通过X射线衍射(XRD),差式扫描量热法(DSC)以及压缩实验研究了Ni,Cu和Nb合金元素对Fe55Ni2Cr12Mo10B6C13Y2, Fe55Cu2Cr12Mo10B6C13Y2和Fe55Nb2Cr12Mo10B6C13Y2合金的非晶形成能力和力学性能的影响.实验结果表明:Fe55Ni2Cr12Mo10B6C13Y2和Fe55Cu2Cr12Mo10B6C13Y2可以形成块体非晶,他们的约化玻璃转化温度Trg为0.57.非晶合金Fe55Ni2Cr12Mo10B6C13Y2和Fe55Cu2Cr12Mo10B6C13Y2具有较高的压缩断裂强度.Fe55Cu2Cr12Mo10B6C13Y2的断裂方式不是沿剪切带断裂,而是断裂成很多碎片.Fe55Ni2Cr12Mo10B6C13Y2断裂时这两种方式共同存在.     

Sn0.5Ti0.5O2固溶体薄膜的制备及其气敏特性研究

采用溶胶凝胶法制备了Sn0.5Ti0.5O2固溶体.用X射线衍射(XRD)和红外(IR)技术对材料的结构和热稳定性进行了分析表征.固溶体的热稳定性与起始反应温度有关,40℃水浴制备的凝胶经过1000℃烧结就发生了相分解,出现了富Sn、富Ti相,而80℃水浴制备的凝胶经过1200℃烧结也不发生相分解,仍以Sn0.5Ti0.5O2相存在.将胶体制成了薄膜元件并测试了元件的气敏性能,发现此元件对H2S气体有一定的灵敏度.     

(1-x)CaTiO_3/xNi_(0.5)Zn_(0.5)Fe_2O_4复合材料的制备及其性能

采用固相反应法合成了(1-x)CaTiO3/xNi0.5Zn0.5Fe2O4(0≤x≤1.0)复合材料,并研究了复合材料的物相、微观结构、介电性能和磁性能。结果表明:样品中仅含有钙钛矿型CaTiO3和尖晶石型Ni0.5Zn0.5Fe2O4。1260℃保温3h,样品相对密度达到98.91%,颗粒尺寸约为2μm。样品介电常数随Ni0.5Zn0.5Fe2O4含量(x)增加而增大。当x=0.7、测试频率为103 Hz时,样品介电常数(εr)和介电损耗(tanδ)分别为2629.18和1.74。(1-x)CaTiO3/xNi0.5Zn0.5Fe2O4复合材料显示磁性。其中x=0.7时,样品饱和磁化强度(Ms)达到49.07A·m2/kg;这归因于Ni0.5Zn0.5Fe2O4具有优异的磁性能。     

Zr4+B位置换对(Pb0.5Ca0.5)(Fe(0.5)Nb0.5)O3

研究了Zr4+离子B位置换改性对(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3陶瓷微波介电性能.实验结果表明,(Pb0.5Ca0.5)(Fe0.5Nb0.5)O3(PCFNZ)陶瓷样品呈现单一斜方钙钛矿相结构.随Zr(4+)离子的置换量增加,PCFNZ陶瓷体系的Qr值和晶粒尺寸逐渐减小;介电常数εr随着置换量增加...     

FeCoBSiNb (Y)合金的玻璃形成能力及磁性能研究

采用铜模真空吸铸法、X射线衍射仪(XRD)、示差扫描量热分析仪(DSC)及振动样品磁强计(VSM),研究稀土元素Y及Fe/Co比例变化对FeCoBSiNb(Y)系合金的玻璃形成能力、热稳定性及磁性能影响.实验结果表明,添加4%(原子分数)的Y有利于(Fe0.5 Co0.5)72B19.2 Si4.8Nb4合金玻璃形成能...     

机械合金化合成Fe-Ni-C系非晶态合金

用机械合金化方法合成了Fe—Ni—C系非晶态合金，用X射线衍射仪对球磨不同时间的Fe—Ni—C系混合粉末进行了分析．结果表明：在Fe—Ni合金中加入C可促使其形成非晶；原子分数分别为Fe40Ni40C20、Fe60Ni20C20的混合粉末在一定的机械合金化条件下可获得非晶．     

BNT-BT和BNT-BKT基无铅压电陶瓷研究进展

综述了Bi0.5Na0.5TiO3-BaTiO3系和Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3系无铅压电陶瓷的最新研究进展.总结了各种添加剂对这两种无铅压电陶瓷体系压电性能的影响机理和规律,介绍了当前以各种工艺对其微观结构和压电性能进行改进的研究成果,并展望了这两种无铅压电陶瓷体系的发展趋势.     

脉冲激光沉积Ba0.5Sr0.5TiO3、Pb0.5Ba0.5TiO3和Pb0.5Sr0.5TiO3薄膜及其介电性质

采用脉冲激光沉积法,在Pt／Ti／SiO2／Si基底上分剐制备厚度为350nm的Ba0.5Sr0.5TiO3(BST)、Pb0.5Ba0.5TiO3(PBT)和Pb0.5Sr0.5TiO3(PST)薄膜并研究了它们的介电性质。XRD显示,在相同的制备条件下三者具有不同的择优取向,PST具有(110)择优取向,PBT具有(111)择优取向,而BST则是混合取向。SEM显示三者样品表面均匀致密,颗粒尺寸大约在50nm至150nm之间。PST与BST、PBT相比有更高的介电常数,在频率为10kHz时,分别为874、334和355,而损耗都较低,分别为0．0378、0．0316和0．0423,同时PST漏电流也是最小的。测量薄膜的C-V特性扣铁电性能表明室温下BST呈现的是顺电相,PST和PBT则呈铁电相。本文也测量了薄膜在不同频率下的介电温度特性,BST、PBT和PST均表现出频率弥散现象,即随着频率的降低．居里温度降低而介电常数会升高。并测得BST和PST的居里温度分剐为-75和150℃。而PBT的居里温度在250℃以上。本文研究表明：与BST相比较,PBT的介电常数与之相近,漏电流较大;而PST具有高介电常数,较小的漏电流和较大的电容-电压调谐度,在相关半导体器件中的应用将有很大的潜力。     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3无铅压电陶瓷的制备与性能

采用传统的干压成型法制备了Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3无铅压电陶瓷,研究了不同K0.5Bi0.5TiO3含量对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3陶瓷的微观结构与电性能的影响规律.结果表明,Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3无铅压电陶瓷随K0.5Bi0.5TiO3含量增加,晶格常数增大,密度减小,晶粒尺寸减小,压电常数先增大后减小,介电常数增大,介电损耗增加,机械品质因数下降,而居里温度不断升高,在200℃附近存在由铁电相向反铁电相转变的一个相变点,组分为0.84 Na0.5Bi0.5TiO3-0.16 K0.5Bi0.5TiO3的陶瓷位于准同型相界附近,具有最佳的压电性能.     

Heat capacity, thermopower and magnetoresistance effects in multiferroic La0.5Bi0.5Mn0.5Fe0.5O3

We have carried out systematic investigations in perovskite multiferroic La_0.5Bi_0.5Mn_0.5Fe_0.5O₃ by means of X-ray diffraction, magnetisation, electrical resistivity, thermoelectric and heat capacity measurements. The magnetic behaviour of this composition is rather complex, though the magnetisation curve seems to be like a weak ferromagnetic material. However, there is no clear evidence of λ-anomaly in the heat capacity data down to 2 K, yet this behaviour corroborate the trends of semiconducting silicon below room temperature. The sensitivity of magnetic behaviour to the iron-manganese ratio is also demonstrated. In presence of an external field of 7 T, it exhibits a magnetoresistance of ?5 % at 130 K. The thermoelectric value increases linearly with decreasing temperature, and at room temperature the value is +85 μV/K, which is associated with the p-type polaronic conductivity.     

Na0.5 Bi0.5 TiO3-K0.5 Bi0.5 TiO3系铁电体的相变研究

研究了(Na1-xKx)0.5Bi0.5TiO3体系x分别为0、0.08、0.16和0.20时陶瓷不同频率下的介电温谱,发现材料为弛豫型铁电体,材料的介电谱在室温到500℃的温度范围内存在一个介电常数-温度"台阶",一个介电常数-温度峰和一个介电损耗-温度峰,通过分析陶瓷不同温度下的电滞回线验证陶瓷在升温过程中产生了铁电-反铁电-顺电相变,采用铁电体成分起伏理论和内电场理论解释了这类弛豫型铁电体相变的原因.     

Superconductivity in Layered CeO0.5F0.5BiS2

We report appearance of superconductivity in CeO_0.5F_0.5BiS₂. The bulk polycrystalline samples CeOBiS₂ and CeO_0.5F_0.5BiS₂ are synthesized by conventional solid state reaction route via vacuum encapsulation technique. Detailed structural analysis showed that the studied CeO_0.5F_0.5BiS₂ compound is crystallized in tetragonal P4/nmm space group with lattice parameters a=4.016(3) Å, c=13.604(2) Å. DC magnetization measurement (MT-curve) shows the ferromagnetic signal at the low temperature region. The superconductivity is established in CeO_0.5F_0.5BiS₂ at $T_{c}^{\mathrm{onset}}=2.5~\mbox{K}$ by electrical transport measurement. Under applied magnetic field, both T _c onset and T _c (ρ=0) decrease to lower temperatures and an upper critical field [H _c2(0)] above 1.2 Tesla is estimated. The results suggest coexistence of ferromagnetism and superconductivity for the CeO_0.5F_0.5BiS₂ sample.     

Positive delayed photoconductivity in double heterostructures Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As of the p-type

Positive delayed photoconductivity was observed for the first time in double p-type heterostructures Al_0.5Ga_0.5As/GaAs/Al_0.5Ga_0.5 As upon exposure to the radiation of a red light-emitting diode. In this state, the concentration and mobility of two-dimensional holes are increased 1.5 and 1.7 times, respectively, as compared to the initial dark values. The delayed photoconductivity can be explained by the presence of deep electron traps located above the Fermi level at the inverted heterointerface.     

Structure and electrical properties of Bi0.5Na0.5TiO3-Y0.5Na0.5TiO3-BaTiO3 lead-free piezoelectric ceramics

New (1 – x ? y)Bi_0.5Na_0.5TiO₃-xY_0.5Na_0.5TiO₃-yBaTiO₃ lead-free ceramics have been prepared by a conventional ceramic fabrication technique, and their structure and electrical properties have been studied. A morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases is formed at 0.04 < y < 0.10. As compared to pure Bi_0.5Na_0.5TiO₃ ceramic, the partial substitutions of Y³⁺ for Bi³⁺ and Ba²⁺ for (Bi_0.5Na_0.5)²⁺ in the A-sites of Bi_0.5Na_0.5TiO₃ lower effectively the coercive field E _c and increase the remanent polarization P _r of the ceramics. Because of low E _c, large P _r and the MPB, the ceramics with x = 0–0.02 and y = 0.06 exhibit the optimum piezoelectric properties: d ₃₃ = 155–159 pC/N and k _p = 28.8–36.7%. The temperature dependences of dielectric properties of the ceramics show relaxor-like behaviors. The ferroelectric properties at different temperature suggest that the ceramics may contain both the polar and non-polar regions near/above T _d.