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Abdul Aziz E. Ahme Muhammad Naeem Ashiq Muhammad Azhar Khan Nazia Karamat Irshad Ali 《自然科学进展(英文版)》2016,26(4):325-333
A series of Mn x Co_(1-x) Fe_(1-y) Nd_yO_3(where x=0.0–1.0 y=0.0–0.1) multiferroic nanocrystals was synthesized via sol-gel auto-combustion technique. The structure was confirmed by X-ray diffraction(XRD)while morphology was investigated by scanning electron microscopy(SEM). The electrical resistivity was observed to increase from 2.14 * 10~7 to 8.77 * 10~9 Ω-cm and activation energy was found to increase from 0.64 to 0.75 e V, while the drift mobility decreased from 4.75 * 10~(-13) to 1.27 * 10~(-15)cm~2V~(-1)S~(-1) by the substitution of Mn and Nd contents. The dielectric constant, dielectric loss and dielectric loss factor decrease with frequency and Mn-Nd contents. The saturation magnetization was increased from 34 to 70 emu g~(-1) while the coercivity decreased from 705 to 262 Oe with the increase of substituents.The increase in electrical resistivity and saturation magnetization while decrease in dielectric parameters and coercivity make these nanomaterials suitable for applications in microwave devices and longitudinal magnetic recording media. 相似文献
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Cd5Se95–xZnx(x=0, 2, 4, 6) glassy alloy has been prepared by a melt-quenching technique. Thin films were deposited by thermal coating unit on ultraclean glass substrate under a vacuum of 10–6Torr. The absence of any sharp peaks in the X-ray diffraction confirms the amorphous nature of thin films. The frequency and temperature dependence of dielectric constant and dielectric loss in the frequency range of 1 kHz to 1 MHz and in the temperature range of 290–370 K were studied. Dielectric dispersion was observed when Zinc(Zn) was incorporated into the Cd–Se system.The increase in dielectric parameter with Zn concentration may be due to increase in defect states. The DC conductivity has been reported to investigate the effect of Zn concentration on DC conduction loss. The results are interpreted in term of dipolar theory for Cd5Se95 and Cd5Se93Zn2samples, while the remaining samples have been explained on the basis of DC conduction loss. It was also observed that the DC conductivity increased with the increase of Zinc concentration, which may be due to the decrease in the band gap near Fermi level. 相似文献
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Au/Zn O/n-Si(MIS)structures were fabricated by using the RF sputtering method and their complex dielectric constant(ε~*=ε’-jε’’),electric modulus(M~*=M′+j M’’)and electrical conductivity(σ=σ_(dc)+σ_(ac))values were investigated as a function of frequency(0.7 k Hz-1 MHz)and voltage(-6–(+6 V))by capacitance-voltage(C-V)and conductance-voltage(G/ω-V)measurements to get more information on the conduction mechanisms and formation of barrier height between Au and n-Si.The lnσ-Lnf plots have two different regions corresponding to low-intermediate and high frequencies.Such behavior of lnσ-lnf plots shows that the existence of two different conduction mechanisms(CMs)at low-intermediate and high frequencies.Moreover,the reverse bias saturation current(I_o),ideality factor(n),barrier height(Φ_(Bo))were determined from the forward bias I-V data and they were found as a strong function of temperature.The value of n especially at low temperature is considerably higher than unity.The values ofΦ_(B0)and standard deviation(σ_s)were found from the intercept and slope ofΦ_(Bo)-q/2k T plots as 0.551 e V and 0.075 V for the region I(80–220 K)and 1.126 e V and 0.053 V for the region II(220–400 K),respectively.The values ofΦ_(Bo)and effective Richardson constant(A~*)were found from slope and intercept of activation energy plots as 0.564 e V and 101.084 Acm~(-2)K~(-2)for the region I and 1.136 e V and41.87 Acm~(-2)K~(-2)for the region II,respectively.These results confirm that the current-voltage-temperature(I-V-T)characteristics of the fabricated Au/Zn O/n-Si SBDs can satisfactorily be explained on the basis of TE theory with double GD of the BHs. 相似文献
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报道了一种简单的液相还原法制备铁钴合金纳米线/棒.以十六烷基三甲基溴化铵(CTAB)为表面活性剂,在90℃时利用水合肼还原Fe2 和Co2 的水和正辛烷的混合溶液得到铁钴合金纳米线/棒.所得样品经X-射线粉末衍射(XRD) ,透射电子显微镜(TEM) ,选区电子衍射(SAED)和振动样品磁强计(VSM)等表征,结果表明延长反应时间,一维铁钴合金纳米结构直径增大但长度没有明显变化,一维铁钴合金纳米材料的室温矫顽力高于体相铁钴合金.该铁磁性纳米线/棒有望应用于催化、生物技术和磁记录器件等领域. 相似文献
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利用点群４／ｍｍｍ的对称性给出了应力作用下的钛酸铋的弹性吉布斯自由能的表达式，并导出了自发应变，介电性质和压电性质。 相似文献
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A lead free multiferroic material,Bi(Co_(0.45)Ti_(0.45)Fe_(0.10))O_3(BCTF45/10)was synthesized by a solid-state reaction route at high temperatures.BCTF45/10 powder was prepared using appropriate raw maretials in oxide powders with methanol medium.As-prepared circular shaped pellets were sintered at 1053 K for 6 h to produce a compact form.Preliminary structural properties and elemental analysis were determined using X-ray diffraction and energy-dispersive X-ray spectroscopy techniques respectively at room temperature.The microstructure or surface morphology of the sintered sample was carried out by using field emission scanning electron microscope(FE-SEM).The XRD analysis shows that the compound exhibits the single-phase of orthorhombic symmetry.The average crystallite size estimated using the Scherrer's technique was found to be 30 nm.The influence of Co and Ti substitution(at Bi and Ti sites of Bi Fe O_3)on some physical and electrical properties of Bi Fe O_3was examined by using phase sensitive multimeter in a wide frequency and temperature ranges.The magnetic nature of the sample was studied using vibrating sample magnetometer.Study of room temperature magnetic hysteresis loop exhibits the enhanced ferromagnetic characteristic with saturation magnetization of 5.091 emu/g and coercive field of 0.213 k Oe respectively.The enhanced magnetic properties highlight various potential applications of Co/Ti doped BCTF45/10 materials. 相似文献
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N2H4.H2O水热体系中,在Zn基底上制备出了ZnO纳米棒薄膜。采用X射线衍射(XRD)、场发射扫描电镜(FESEM)及发致发光谱(PL)等分析测试手段,研究了ZnO薄膜的形貌结构和发光特性。结果表明,预处理工艺不同,Zn基底表面状态不同,ZnO薄膜形貌也不同。在经预氧化形核的Zn基底上易于制备ZnO纳米棒薄膜。在单一取向的Zn基面上,易于制备ZnO纳米棒阵列。PL测试分析表明,ZnO纳米棒有强的近带边紫外光发射峰和弱的缺陷发射峰。阵列棒本征发射峰强度最高、缺陷峰最弱,反映了该ZnO纳米棒结晶质量高。 相似文献
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应用水热方法,合成了直径约30nm的ZnO纳米棒并通过X射线衍射、透射电子显微镜和拉曼光谱对其结构进行表征.还研究了他们的光学性质,如:室温下的光致发光谱以及温度依赖的光致发光光谱.研究结果显示,反应溶液的pH值修饰了ZnO纳米棒的长径比.观测到了ZnO纳米棒中源自激子的紫外发光(3.2eV)和来自于深能级缺陷的可见发光(2.0eV).根据变温发射光谱,通过对实验数据的拟合获得了一些重要的参数,如:激子的爱因斯坦温度及深能级的热激活能等. 相似文献
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The frequency-dependent dielectric dispersion of ZnO-Na2O-AI2O3-B2O3 (in mol％)glass prepared by the melt quenching technique is investigated in the temperature ranges from room temperature to 420 K.Die... 相似文献
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采用微波-水热法(M-H)制备了钛酸钡(BaTiO3)纳米晶，用透射电镜(TEM)、粉末X-ray衍射(XRD)分析、热失重(TGA)分析等手段对其晶体形貌、结构进行了研究．结果表明：这种M-H法在低温(60～160℃)条件下可得到颗粒约为20～30nm的立方相BaTiO3纳米晶体．通过对材料介电性能的研究发现，纳米材料的静态介电常数远大于常规材料的介电常数，并随着颗粒粒径的减小，纳米材料的介电常数先增大而后有所降低。 相似文献
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以乙醇-水混合溶液为溶剂,160℃T成功合成了Eu3+掺杂的LaVO4纳米棒.用X射线衍射(XRD)、透射电子显微镜(TEM)和光致发光(PL)等技术时样品进行表征.XRD和TEM测试结果说明LaVO4:Eu3+纳米棒是纯锆石型四方相结构、晶体结构均匀、没有缺陷,通过调节溶液pH和反应时间能够控制LaVO4:Eu3+纳米的定向组装和晶体生长.PL光谱显示Eu3+掺杂可以显著提高LaVO4纳米棒的荧光性能.另外,对LaVO4:Eu3+纳米棒的形成机制进行了研究. 相似文献
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Peng-fei Yin Xiang-yu Han Chao Zhou Chuan-hui Xia Chun-lian Hu Li-li Sun 《矿物冶金与材料学报》2015,22(7):762-769
Rhombohedral-phase NiS micro/nanorods were synthesized on a large scale through a hydrothermal method using NiCl2·6H2O and thiourea crystals as starting precursors. Recrystallized thiourea was observed to play an important role in the formation of micro/nanosized rods and flower-like structures. The molar ratio and reaction temperature of the precursors influenced the morphology and phase of NiS products. Pure rhombohedral NiS micro/nanorods were obtained on a large scale when the molar ratio between NiCl2·6H2O and thiourea crystals was fixed at 2:1, and the mixture was heated at 250℃ for 5 h. Flower-like NiS nanostructures were formed when the molar ratio between NiCl2·6H2O and thiourea crystals was maintained at 1:1. The Raman and Fourier-transform infrared (FTIR) spectra of the as-prepared rhombohedral NiS micro/nanorods were collected, and their magnetic properties were investigated. The results showed that the FTIR absorption peaks of the as-prepared product are located at 634 cm-1 and their Raman peaks are located at 216 and 289 cm-1; the as-prepared NiS micro/nanorods exhibited weak ferromagnetic behavior due to the size effect. 相似文献
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研究了初始粉体中的氧化铅欠缺对PZN基预烧粉体和无铅气氛烧结的陶瓷的相组成和介电性能的影响。研究发现：任何微量的铅欠缺都会使预烧粉体和陶瓷中产生焦绿石相,而且随着氧化铅欠缺量的增加预烧粉体和陶瓷中的钙钛矿相含量逐渐地下降。随着铅欠缺量的增加,PZN基陶瓷的介电常数大幅度地增加,但是铅欠缺对介电损耗影响很小。介电常数的增加主要是由于“有效有序微区”尺寸的增大和晶界间过量氧化铅层的消除。 相似文献
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采用两步法制备三维石墨烯/WO_3纳米棒/聚噻吩(3D-rGO/WO_3/PTh)三元复合材料,首先合成二元复合材料三维石墨烯/WO_3纳米棒(3D-rGO/WO_3),然后以此为载体,通过噻吩(PTh)单体的原位聚合得到最终产物。通过X射线衍射(XRD)、傅里叶红外光谱(FTIR)、场发射扫描电镜(FESEM)和透射电镜(TEM)对合成材料进行表征,研究了其低温气敏性能,分析了三元复合材料的气敏机理。结果表明,复合3D-rGO与PTh后三元复合材料的工作温度降低,75℃时对200 mg/L H2S的灵敏度达到25. 2,对H_2S有较高的灵敏度,响应和恢复时间较短。 相似文献
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采用六角氮化硼(h-BN)粉末为原料,通过对h-BN粉末球磨得到BN纳米粉,并在管式炉中对BN纳米粉进行烧结,烧结环境分别为真空和空气.利用X射线衍射(XRD)和透射电子显微镜(TEM)研究所得样品的结构和成分.结果表明,样品为结晶较好的BN-B2O3纳米棒复合材料. 相似文献
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Xingwang Zhang Zhigang Yin Faitong Si Hongli Gao Xin Liu Xiulan Zhang 《科学通报(英文版)》2014,59(12):1280-1284
Cubic boron nitride(c-BN)thin films were deposited on Si substrates by applying ion beam assisted deposition and then doped by S ion implantation.To produce a uniform depth profile of S ions in c-BN films,the implantation was carried out for the multiple energies.A slight degradation of c-BN crystallinity resulted from ion implantation can be recovered by thermal annealing,keeping the cubic phase content as high as 92%.The resistance reduces from 1010X for the as-deposited c-BN film to 108X after an S implantation of 5 9 1014ions cm-2and annealing at 1,173 K,suggesting an electrical doping effect of S dopant.The electrical resistance of the S-doped c-BN thin film decreases with increasing temperature,indicating semiconductor characteristics.The activation energy of S dopant is estimated to be 0.28±0.01 eV from the temperature dependence of resistance. 相似文献
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高铝水泥基MDF材料的介电性能研究 总被引：5，自引：1，他引：5
本文报导了某些因素对高铝水泥基ＭＤＦ材料介电常数和介电损耗的影响。实验结果表明：ＭＤＦ材料的介电常数和介电损耗均与交电电频率有关；当聚合物掺量增加时，介电常及介电损耗均减小；采用热压成型的ＭＤＦ材料比雾室养护的ＭＤＦ材料具有较低的介电常数及介电损耗；用硅灰改性可使介电常数和介电损耗进一步降低。 相似文献