共查询到18条相似文献,搜索用时 234 毫秒
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用分析电镜和高分辨电镜对在30mm×30mmLaAlO3衬底上,采用中空柱状阴极直流磁控溅射的高JcYBa2Cu3O7-x(YBCO)薄膜的微观组织结构进行了研究。薄膜为c轴取向YBCO,含有少量Y2BaCuO5颗粒和纺锤状Y2O3。膜内主要晶体缺陷为[001]刃位错和螺位错、堆垛层错、(001)晶面弯曲带、小于15nm的晶格畸变区和阳离子空位。LaAlO3衬底表面呈阶梯状并有小坑。衬底表面第一层膜原子为CuO和CuO2层,以致在界面形成BaCuO2和YaBaCu2O5相。LaAlO3衬底表层有较多位错,对薄膜外延生长和缺陷的形成有明显影响。 相似文献
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用固相反应法制备出LaBa_2Cu_2MO_7(M=Ga,Co)新相。X射线衍射分析认为其属四方晶系,La-Ba_2Cu_2GaO_7的;LaBa_2Cu_2CoO_7的。电阻和温度关系曲线测定表明均为半导体。 相似文献
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含氟Y-Ba-Cu-O高温超导体稳定性与结构的研究 总被引:1,自引:0,他引:1
应用BaF2、CuF2和YF3分别部分代换BaO、CuO和Y2O3制得了一系列带有氟元素的Y-Ba-Cu-O高温超导体样品,其中BaF2代换BaO的摩尔量可达45%,样品的零电阻温度为82.5~93.5K。应用XRD、DTA、IR和化学方法研究了样品的结构和稳定性。初步实验结果表明,氟元素只有少量进入超导相,但含氟的Y-Ba-Cu-O超导体在水蒸气和二氧化碳中的稳定性则大大提高。 相似文献
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研究了YBa2Cu3O6~7超导催化剂上CO加氢反应,反应主要产物是甲醇和二甲醚。利用原位FTIR、XPS和XRD技术对催化剂进行了表征。原位FTIR结果表明,反应中间物可能为醛基、甲氧基和甲酸根。CO吸附到YBa2Cu3O6~7上与晶格氧发生反应生成CO2,YBa2Cu3O6~7产生氧空位并由Orthorhombic相转变为Tetragonal相。 相似文献
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La0.5R0.5Ba2Cu3O7,Pr0.5R0.5Ba2Cu3O7以及RBa2Cu3o7(R=稀土)的键共价性计 总被引:2,自引:1,他引:1
使用复杂晶体化学键理论计算了La0.5R0.5Ba2Cu3O7(R=Pr,Nd,Sm,Eu,Gd,Dy,Y,Ho,Er,Tm,Yb,Lu)(La-R123),Pr0.5R0.5Ba2Cu3O7(R=La,Nd,Sm,Eu,Gd,Dy,Ho,Y,Er,Tm,Yb,Lu)(Pr-R123)以及RBa2Cu3O7(R=La,Pr,Nd,Sm,Eu,Gd,Dy,Ho,Y,Er,Tm)(R123)中Cu-O键的键共价性,结果表明Pr-R123,La-R123,以及R123都应具有超导性,而实验结果是La0.5Pr0.5Ba2Cu07,R0.5,Pr0.5Ba2Cu3O7(R=La,Nd,Sm,Eu,Gd)无超导性,产生这种矛盾的原因尚不明确,需要做进一步的研究。 相似文献
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La—Ba—Cu复合氧化物在催化消除NO反应中催化性能的研究 总被引:2,自引:0,他引:2
合成了具有钙钛石结构的复合氧化物YBa2Cu3O7、LaBa2Cu3O7、LaBaCu2O5、La2BaCu3O7和La4BaCu5O12。考察了它们对NO分解和NO+CO反应的催化性能。结合化学分析、XRD、TPD和TPR对催化剂的表征结构,探讨了该系列复合氧化物对NO分解和NO+CO反应的催化机理。 相似文献
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用PMP生长方法制备YBa2Cu3O7大尺寸块材,通过调整成分和工艺,制备出直径3.5cm,厚,0.9cm的圆片,利用表磁约0.3T的NdFeB永磁体,能将1.3kg重的物体悬浮起1mm左右的高度,XRD和SEM观察表明,弥散的Y2BaCuO5细小颗粒以及添加适量的银,对磁悬浮性能的提高有着重要作用。 相似文献
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Zhu Z Gao D Dong C Yang G Zhang J Zhang J Shi Z Gao H Luo H Xue D 《Physical chemistry chemical physics : PCCP》2012,14(11):3859-3863
Nanoparticles of superconducting YBa(2)Cu(3)O(7-δ) were synthesized via a citrate pyrolysis technique. Room temperature ferromagnetism was revealed in the samples by a vibrating sample magnetometer. Electron spin resonance spectra at selected temperatures indicated that there is a transition from the normal to the superconducting state at temperatures below 100 K. The M-T curves with various applied magnetic fields showed that the superconducting transition temperatures are 92 K and 55 K for the air-annealed and the post-annealed samples, respectively. Compared to the air-annealed sample, the saturation magnetization of the sample by reheating the air-annealed one in argon atmosphere is enhanced but its superconductivity is weakened, which implies that the ferromagnetism maybe originates from the surface oxygen defects. By superconducting quantum interference device measurements, we further confirmed the ferromagnetic behavior at high temperatures and interesting upturns in field cooling magnetization curves within the superconducting region are found. We attributed the upturn phenomena to the coexistence of ferromagnetism and superconductivity at low temperatures. Room temperature ferromagnetism of superconducting YBa(2)Cu(3)O(7-δ) nanoparticles has been observed in some previous related studies, but the issue of the coexistence of ferromagnetism and superconductivity within the superconducting region is still unclear. In the present work, it will be addressed in detail. The cooperation phenomena found in the spin-singlet superconductors will help us to understand the nature of superconductivity and ferromagnetism in more depth. 相似文献
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MENG Jian REN Yu-Fang LI Xiao-GuangLaboratory of Rare Earth Chemistry Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin ChinaPopov V.V. Repin S.M. Smirnov LA. loffe Physicotechnical Institute Russian Academy of Sciences Saint Petersburg Russia 《中国化学》1994,12(5):419-424
YBa2Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected as an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)-O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of YBa2Cu3-xVxO7-v and also results in a depression of TC. 相似文献
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The calculations of clusters modeling the fluorine-doping and oxygen deficiency of YBa2Cu3O2,have been performed by the method of all-electron ab initio Hartree-Fock with self-consistent crystal field Results show that in CuO planes electric charge significantly increases,the chemical valence of Cu decreases and the covalent bonding of Cu-O greatly weakens owing to oxygen deficiency,while the effect of F restores the local electronic structure of YBa2Cu3O7 The reported opinion that F occupied the oxygen vacancy in Cu-O chains seems disputable according to the calculated bonding characteristics. 相似文献
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Li Ming 《International journal of quantum chemistry》1994,50(4):233-242
Based on the EHMO approach, an approximate treatment of electronic energy-band structures is suggested. By employing this treatment, computations of the band structures for the Al-doped superconductors YBa2Cu3–xAlxO7 + δ were carried out. It is shown by analysis of the band structures and the density of states that the 2D Cu–O planes in the Y? Ba–Cu? O superconducting system play a dominant role in superconductivity, whereas the 1D Cu? O ribbons have indirectly an influence on superconductivity through the connection of the O(4) atoms to two Cu? O planes. © 1994 John Wiley & Sons, Inc. 相似文献
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La-Ba-Cu复合氧化物在催化消除NO反应中催化性能的研究 总被引:3,自引:0,他引:3
合成了具有钙钛石结构的复合氧化物YBa2Cu3O7、LaBa2Cu3O7、LaBaCu2O5、La2BaCu3O7和La4BaCu5O12.考察了它们对NO分解和NO+CO反应的催化性能.结合化学分析、XRD、TPD和TPR对催化剂的表征结果,探讨了该系列复合氧化物对NO分解和NO+CO反应的催化机理. 相似文献
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研究钴离子部分取代铜离子对YBa2Cu3O6+δ的氧非计量值δ和氧渗透率的影响.对于钴替代的样品,氧非计量的绝对值变大,且其数值不再随温度和氧分压的变化发生显著变化.YBa2Cu2CoO6+δ样品在中、高温具有可观的氧渗透率.对于厚度为1.2 mm的致密YBa2Cu2CoO6+δ样品,在850℃时,只要在样品两端施加较小的氧分压差(PO2=21.2 kPa、 PO2=101 Pa),其氧渗透率即可达57 μmol/cm2 s, 明显高于YBa2Cu3O6+δ的氧渗透率(31 μmol/cm2 s).YBa2Cu2CoO6+δ的高氧渗透率在结构上可被归结为位于晶胞基面上的氧离子和氧空位的均匀分布. 相似文献
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研究了YBaCu3O6~7超导催化剂上CO2的加氢制醇反应。考察了温度、压力和空速等条件对催化剂反应性能的影响。反应的主要产物是甲醇、CO和少量甲醚。利用XPS、XRD和AFM等技术对催化剂的结构、铜的存在状态和反应活性位进行表征发现,在反应过程中,YBa2Cu3O6~7由orthombic相转变为tetragonal相。反应活性位可能是Cu(I)物种。反应后催化剂颗粒的分散程度明显提高 相似文献