共查询到20条相似文献,搜索用时 11 毫秒
1.
本介绍了基于混合物理化学气相沉积法(HPCVD),以B2H6为硼源,在(000l)取向的Al2O3单晶衬底上,制备了MgB2超导体厚膜样品.该样品平均厚度约为40μm.其Tc(onset)=39K,Tc(0)=37.2K.X光衍射图显示该膜沿(101)方向生长,具有少量Mg和MgO杂相.SEM图像、X射线能量损失谱以及背散射电子衍射图证实了这两种杂相的存在,并显示该样品成分富镁.样品表面的镁与空气接触形成MgO膜,在一定程度上阻止了MgB2样品进一步被氧化.对于MgB2厚膜成膜过程及反应机理,我们提出了一种新的推断. 相似文献
2.
Zhang Jia Jing-pu Guo Ying Lu Xin-feng Wang Chin-ping Chen Jun Xu Xiao-nan Wang Meng Zhu Qing-rong Feng 《Frontiers of Physics》2006,1(1):117-121
Superconducting MgB2 thick film has been prepared via hybrid physical-chemical vapor deposition method on Al2O3 (0001) substrate by using B2H6 and magnesium ingot as raw materials reacted from 730 to 830°C for 40 min under 20 to 30 kPa. Its thickness is about 40 µm. The MgB2 thick film shows T c (onset) = 39.0 K and T c (0) = 37.2 K. X-ray diffraction pattern shows that the film grown along (101) direction has small amount of impurities of Mg and MgO. Scanning electron microscopy and energy dispersive X-ray spectroscopy indicated that these impurities existed indeed and were Mg rich. The MgO film was formed on the surface of the MgB2 thick film to further protect the sample from oxidation. We presented a new mechanism for the formation of the thick film. 相似文献
3.
4.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
5.
6.
MK Bhide RM Kadam MD Sastry Ajay Singh Shashwati Sen Manmeet Kaur DK Aswal SK Gupta VC Sahni 《Pramana》2002,58(5-6):799-802
Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for
polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave
absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime. 相似文献
7.
Zhuang Cheng-gang An Ling Chen Li-ping Ding Li-li Zhang Kai-cheng Chen Chin-ping Xu Jun Feng Qing-rong Gan Zi-zhao 《Frontiers of Physics in China》2006,1(2):246-250
We fabricated several superconducting MgB2 thick films on stainless steel (SS) substrates by using hybrid physical-chemical vapor deposition (HPCVD) technique. The
thickness was in the 10μm to 20μm range, and the onset critical transition temperature T
c (onset) and the width of the superconducting transition (ΔT) were about 37.8 and 1.2 K. They were dense and textured along (101) direction with high tenacity, despite the existence
of a little amount of MgO and Mg. We bent the films at different degrees and studied the ductility and transport properties
of these MgB2 thick films under applied force. The results demonstrated that the superconducting properties of these thick films, prepared
by HPCVD, stay almost unaffected even with the films bent to a large degree with a curvature of 0.5 mm. This indicated that
the superconducting wires or tapes of MgB2 with a core of SS had the advantages of avoiding rigidity and brittleness in industrial handling. The technique of HPCVD
has, therefore, a high application potential.
__________
Translated from Chinese Journal of Low Temperature Physics, 2005, 27(2) (in Chinese) 相似文献
8.
Li Fen Guo Tao Zhang Kai-cheng Chen Chin-ping Feng Qing-rong 《Frontiers of Physics in China》2006,1(4):446-448
Thick MgB2 (magnesium diborate) films, ∼10 μm, with T
c (onset) = 39.4 K and T
c (zero) = 39.2 K have been successfully grown on a stainless steel substrate using a technique called hybrid physical-chemical
deposition (HPCVD). The deposition rate is high, ∼6.7 nm/s. The X-ray diffraction (XRD) indicates that it is highly (101)
and c-axis oriented. The scanning electron microscope (SEM) images demonstrate that the film grown is in “island-mode”. The uniform
superconducting phase in the film is shown by the M-T measurement. 相似文献
9.
High-density MgB2 (HD-MgB2) superconducting samples (D ⩾ 2.2 g/cm3), using different sources of magnesium powder as raw material, were synthesized in ambient pressure in a rich Mg environment.
The magnesium powders used in the fabrication process include nanometer-sized magnesium particles, powders from Alfa Aesar,
ordinary off-the-shelf powder, and magnesium chip. The fabrication procedure involved a double-sintering process in a rich-Mg
environment. A transition temperature T
c of 39 K was observed. Samples with the equally high density and matching superconducting properties were obtained as well
by a triple sintering process of the MgB2 powder directly from Alfa Aesar.
相似文献
10.
The influence of shock-wave pressure treatment up to 65 GPa on the crystal structure and the superconducting transition temperature of a polycrystalline MgB2 sample has been investigated. X-ray diffraction measurements have revealed that the shock-wave pressure does not result in any irreversible structural phase transitions in the MgB2, except for microdistortions formed in the crystal structure of the shock-wave pressure-treated MgB2 sample. This conclusion is in agreement with the results of superconducting transition temperature measurements of a MgB2 sample performed before and after its shock-wave pressure treatment. 相似文献
11.
Fast photoelectric effects have been observed in MgB2 thin film
fabricated by chemical vapour deposition. The rise time was $\sim $10
ns and the full width at half-maximum was \sim185\,ns for the photovoltaic
pulse when the film was irradiated by a 308\,nm laser pulse of 25\,ns in
duration. X-ray diffraction and the scanning electron microscope revealed
that the film was polycrystalline with preferred c-axis orientation. We
propose that nonequilibrium electron--hole pairs are excited in the grains
and grain boundary regions for MgB2 film under ultraviolet laser and
then the built-in electric field near the grain boundaries separates
carriers, which lead to the appearance of an instant photovoltage. 相似文献
12.
我们对用纳米镁粉(平均颗粒度≤40nm)在常压下制备MgB2超导样品(以下简称纳米MgB2超导样品)进行了研究.得到了一组与用普通颗粒镁粉分别在真空条件下和流动氩气下制备MgB2超导样品时得到的原位ρ-T曲线不同的曲线.实验结果表明纳米MgB2超导样品的成相温区是430℃到490℃之间,低于用普通颗粒镁粉分别在真空条件下和流动氩气下制备MgB2超导样品时的成相温度:640℃~700℃和530℃~630℃.所得到的纳米MgB2超导样品的密度是1.46g/cm3.它高于用其他各种镁粉原料在常压下制备通过一次烧结制得的MgB2超导样品. 相似文献
13.
我们用混合物理化学气相沉积(Hybridphysicalchemicalvapordeposition简称为HPCVD)法在αAl2O3(00l)衬底上原位制备了一批超导性能良好的外延MgB2超导薄膜样品.用10%浓度的乙硼烷(B2H6)氢气混合气作为原料,研究了不同条件对MgB2薄膜沉积速率的影响.在一定条件下制备了一批MgB2薄膜,厚度为200nm左右,样品的零电阻转变温度(Tc0)最高达到39K.X射线衍射分析的θ~2θ扫描表明,MgB2薄膜的晶粒都具有较好的C轴取向,对样品的(101)面Φ扫描结果显示MgB2薄膜晶格与衬底有很好的外延取向,取向关系为[1010]MgB2∥[1120]Al2O3.由毕恩模型计算求得在5K和零场条件下,样品的临界电流密度Jc=9.8×106A/cm2.这些结果表明HPCVD技术在MgB2外延薄膜原位制备方面有着很大的优势,从而有利于实现MgB2薄膜在电子器件方面的应用. 相似文献
14.
采用聚苯乙烯小球修饰Ti片表面,并进行阳极氧化,制备出一种由纳米颗粒和纳米管构成的TiO2膜.通过数值模拟,分析了氧化表面附近的局部电场分布对TiO2膜形貌的影响.结果表明,覆盖物增强了局部电场,从而加快了O2-与Ti的反应速率,有利于TiO2的生长;与此同时,[TiF6]6-的扩散受到阻碍,使得TiO2的溶解速率减慢.可见,覆盖物打破了TiO2纳米管形成的平衡条件,导致纳米颗粒的生成.此外,通过X射线衍射和Raman光谱的测试分析发现,所制备的TiO2为锐钛矿结构. 相似文献
15.
报道了利用蓝宝石介质谐振器技术测量MgB2超导薄膜的微波表面电阻Rs sub>、0K时的穿透深度λ(0)和超导能隙Δ(0).λ(0)和Δ(0)的值是通过先测量样品穿透深度λ(T)的变化量Δλ(T),然后由BCS理论模型拟合Δλ(T)的实验数据得到的.测试样 品是利用化学气相沉积技术在MgO(111)基片上制备的c轴织构的MgB2超导薄膜, 薄膜的超导转变温度和转变宽度分别为38K和01K.微波测试结果表明在10K,18GHz下M gB2薄膜的Rs约为100μΩ,可以和高质量的YBCO薄膜的Rs值相比拟;BCS理论拟合得到的MgB2超导薄膜的λ(0)=102nm,Δ(0)=113k Tc. 相似文献
16.
用溶胶-凝胶方法制备了TiO2纳米样品,并对该样品在300℃到800℃温度区域进行了退火处理.应用同步辐射X射线粉末衍射(XRD)方法研究了经不同热处理温度的TiO2纳米颗粒的结构相变.应用同步辐射小角X射线散射(SAXS)方法研究了TiO2纳米颗粒的表面分形与界面特性.得到纳米颗粒粒度与退火温度的变化规律,讨论了表面界面特征与相变的关系.
关键词:
X射线小角散射
X射线衍射
2纳米颗粒')" href="#">TiO2纳米颗粒 相似文献
17.
利用混合物理化学气相沉积法在6H-SiC(001)衬底上制备干净的MgB2超导超薄膜.在本底气体压强、载气氢气流量等条件一定的情况下,改变B2H6流量及沉积时间,制备得到不同厚度的系列MgB2超薄膜样品,并研究了超导转变温度Tc、剩余电阻率ρ(42K)、上临界磁场Hc2等与膜厚的关系.该系列超薄膜沿c轴外延生长,随膜厚度的变小,Tc(0)降低,ρ(42K)升高.膜在衬底上的生长遵循Volmer-Weber岛状生长模式.对于厚度为7.5 nm的MgB2超薄膜,Tc(0) =32.8 K,ρ(42K) =118 μΩcm,是迄今为止所观测到的厚度为7.5 nm的MgB2超薄膜最高的Tc值;对于厚度为10 nm的MgB2膜,Tc(0)=35.5 K,ρ(42K)=17.7 μΩcm,上临界磁场μ0Hc2估算为12 T左右,零磁场、4 K时的临界电流密度Jc=1.0×107 A/cm2,是迄今为止10 nm厚MgB2超薄膜的最高Jc值,且其表面连接性良好,均方根粗糙度为0.731 nm.这预示MgB2超薄膜在超导纳米器件上具有广阔的应用前景.
关键词:
2超薄膜')" href="#">MgB2超薄膜
薄膜生长
氢气流量
混合物理化学气相沉积 相似文献
18.
在室温及不同的氧氩比条件下,采用射频磁控溅射Ag层和直流磁控溅射SnO2层,在载玻片衬底上制备出了SnO2/Ag/SnO2多层薄膜.用霍尔效应测试仪、四探针电阻测试仪和紫外-可见-近红外光谱仪等表征了薄膜的电学性质和光学性质.实验结果表明:当氧氩比为1:14时,所制得的薄膜的光电性质优良指数最大,为1.69×10-2 Ω-1;此时,薄膜的电阻率为9.8×10-5 Ω·cm,方电阻为9.68 Ω/sq,在400~800 nm可见光区的平均光学透射率达85%;并且,在氧氩比为1:14时,利用射频磁控溅射Ag层和直流磁控溅射SnO2层在PET柔性衬底上制备出了光电性质优良的柔性透明导电膜,其在可见光区的平均光学透过率达85%以上,电阻率为1.22×10-4 Ωcm,方电阻为12.05 Ω/sq. 相似文献
19.
利用电泳技术在高熔点金属基底Ta,Mo和W上制备MgB2超导厚膜.厚膜中的MgB2晶粒结合紧密,粒度小于1μm,呈随机取向生长.电阻测量表明沉积在Ta,Mo,W上的MgB2厚膜的超导起始转变温度分别为36.5K,34.8K,33.4K,对应的转变宽度为0.3K,1.5K和2.0K.三种基底上制备的MgB2厚膜的临界电流密度在不同温度下随外磁场的变化情况 基本相同,MgB2/Mo厚膜的临界电流密
关键词:
2超导厚膜')" href="#">MgB2超导厚膜
电泳
金属基底 相似文献