**钇钡铜氧**，或称**钇钡铜氧化物**、**YBCO**，是化学式为YBa2Cu3O7的化合物。它是著名的高温超导体，属于第二类超导体，并且是第一个制得转变温度在液氮沸点以上的材料。

历史
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在发现超导性后的第75年，在苏黎世IBM工作的约翰内斯·贝德诺尔茨和卡尔·米勒发现特定的半导体氧化物可以在低于35K的温度下显示出超导性，特别是镧钡铜氧化物，一种缺氧钙钛矿型的潜在材料。

在此基础上，1987年，阿拉巴马大学亨茨维尔分校的吴茂昆及其研究生（Ashburn和Torng），与休斯顿大学的朱经武和他的学生共同发现了钇钡铜氧，也因此引发了对新高温超导材料的研究热潮。

YBCO是首个超导温度在77K以上的材料，也就是说它的转变温度高于液氮的沸点，用相对便宜的液氮就可以冷却。之前发现的超导体都必须用液氦或液氢冷却（Tb = 20.28 K）。

合成
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YBCO最早是通过在1000-1300K加热金属碳酸盐混合物制备的。

4BaCO3 + Y2(CO3)3 + 6 CuCO3 → 2 YBa2Cu3O{7-x} + 13 CO2 + (3+x)O2
现在YBCO的制取以相应的硝酸盐和氧化物为原料。

YBa2Cu3O{7-x}的超导性质与x值（氧含量）很有关系，只有满足0≤x≤0.5的材料在Tc温度下有超导性，当x~0时其转变温度最高，为95K。

除了氧的计量比外，YBCO的性质也由结晶方式决定。在烧结YBCO时必须小心，因为YBCO是晶体材料，只有小心控制退火和淬火的温度和速度，校准晶界，才可以使其超导性达到最佳。

吴茂昆和同事提出了其他合成YBCO的方法，比如化学气相沉积（CVD）、溶胶-凝胶以及气溶胶法。这些方法在烧结时仍然需要小心。

结构
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YBCO结构
YBCO为钙钛矿缺陷型层状结构，含有CuO-CuO2-CuO2-CuO交替的层，CuO2层可以有变形和皱褶。
钇原子存在于CuO2和CuO2层中，BaO层则在CuO与CuO2两层之间。

当YBa2Cu3O7中氧原子计量小于7时，根据具体数值的不同，这些非计量化合物结构可以有差异，可以化学式中的δ来表示。\delta  = 1时为四方结构，CuO层（Cu(1)）的O(1)为空，不显示超导性。略微增加氧的含量会增加O(1)的占有率。δ< 0.65时*b*轴形成Cu-O链，结构变为正交，晶格参数分别为a=3.82、b=3.89及其c=11.68Å。当δ ~0.07时超导性最佳，O(1)中只有少数几个为空。

有证据显示，当其它原子取代Cu和Ba[來源請求]时，超导性发生在Cu(2)O层，Cu(1)O(1)链只用作储存电荷（charge reservoirs）。然而镨取代钇后形成化合物的超导性与此相矛盾。

钇钡铜氧的超导长度规表现出各向异性，穿透深度 \lambda\_{ab}\approx150~\textrm{nm} ，\lambda\_{c}\approx800~\textrm{nm} ，相干长度 \xi\_{ab}\approx2~\textrm{nm} ，\xi\_{c}\approx0.4~\textrm{nm} 。虽然a-b平面的相干长度是*c*轴的6倍之多，但与传统的超导体，如铌（\xi \approx40~\textrm{nm}）相比仍显得较小。这意味着其超导态易受到界面或晶胞缺陷的影响，因此对制作YBCO时的仪器要求增高，并且YBCO对潮湿环境相当敏感。

应用
--

钇钡铜氧
高温超导体有很多实际中的应用，例如可用作核磁共振成像、磁悬浮设施以及约瑟夫森结中的磁体。

主要有两个问题限制了YBCO在超导方面的应用：

* 第一，YBCO单晶有很高的临界电流密度，至于多晶则很低（保持超导态时仅能通过很小的电流）。这是由材料的晶粒界面造成：当晶界角大于约5°时，超导电流就无法越过界面。这个问题可由通过化学气相沉积制备薄膜或调准晶界得到改善。
* 第二，此类的氧化物材料很脆，以传统方法制成线状并不能很好地保留其超导性质。

另外，很多情况下大规模冷却物体至液氮的温度并不十分实际。

YBCO的表面特性
---------

表面改性常会导致材料的新性质。表面改性的YBCO可衍生出许多性质，如抑制腐蚀、黏合聚合物、成核，制备有机超导体/绝缘体/高温超导体以及制备金属/绝缘体/超导体隧道结。

这些分子层状材料可用循环伏安法制备。目前已制得烷基胺、芳香胺和硫醇与YBCO形成的材料，它们稳定性不一。有理论认为在这其中胺扮演路易斯碱，与YBa2Cu3O7中路易斯酸性的Cu位点结合生成稳定的配位键。

磁悬浮
---

YBCO和其他超导体一样，在转变温度会发生迈斯纳效应。在该温度或低于该温度时，YBCO变为抗磁性，內部磁通量为零，磁力线无法进入超导体，超导体排斥体内的磁场。因此这时超导体表面的任何磁铁都会悬浮起来，见下方的影片。

影片
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| 视频圖示 | 
**钇钡铜氧的超导性质**

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钇钡铜氧磁悬浮录像（360KB，Ogg/Theora格式）。

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| 無法正常觀看？请参见媒体帮助 |

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参考资料
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### 註釋

1. ↑  R. Swarup, A. K. Gupta and M. C. Bansal.. Journal of Superconductivity. 1995, **8** (3): 361–364. doi:10.1007/BF00728172.
2. 1 2 3 4  C. E. Housecroft, A. G. Sharpe and C. E. Housecroft.. Harlow ; Upper Saddle River, NJ: Pearson Prentice Hall. 2005. ISBN 0130399132.
3. 1 2 3 4  N. N. Greenwood and A. Earnshaw.. Boston, Mass.: Butterworth-Heinemann. 1997. ISBN 0750633654 (pbk.) 请检查`|isbn=`值 (帮助).
4. ↑  Yang-Kook Sun, In-Hwan Oh *Ind. Eng. Chem. Res.* **1996**, 35, 4296
5. ↑  Zhou, Derong.. University of Cincinnati. 1991  [2008-05-07]. （原始内容 (Ph.D. Thesis)存档于2007-12-20）.
6. ↑  Oka, et al. *Physica C*, v 300, n 3-4, **10 May 1998**, 200-6
7. ↑  Xu *et al.* *Langmuir*, **1998**, 14 (22)

### 參考文獻

* （页面存档备份，存于）

外部链接
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* （页面存档备份，存于）
* 超导体应用
* MSDS资料页 （页面存档备份，存于）

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| * 
* 论
* 编
**钇化合物** |
| --- |
|  |
| 

|  |  |  |  |  |
| --- | --- | --- | --- | --- |
| YH3 |  |  |  | He |
| LiYF4 | Be | YB6（法语：）Y(BH4)3 | Y(HCOO)3Y(CH3COO)3Y(C2H3O3)3（俄语：） | Y(NO3)3 | Y2O3Y(OH)3 | YF3LiYF4 | Ne |
| Na | Mg | Al | YSi2 | YPO4 | Y2S3Y2(SO4)3 | YCl3Y(ClO4)3 | Ar |
| K | Ca | Sc | Ti | Y2V2O7YVO4 | Cr | Mn | Fe | Y[Co(CN)6] | Ni | YBa2Cu3O7 | Zn | Ga | Ge | YAsYAsO4 | Y2Se3Y2(SeO4)3 | YBr3 | Kr |
| Rb | Sr | Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd | In | YSn3（俄语：） | YSb | Y2Te3 | YI3 | Xe |
| Cs | YBa2Cu3O7 | 镧系 | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn |
| Fr | Ra | 锕系 | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
|  |  | ↓ |  |  |
| 镧系 | La | Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu |
| 锕系 | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |

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| * 
* 论
* 编
**钡化合物** |
| --- |
|  |
| 

|  |  |  |  |  |
| --- | --- | --- | --- | --- |
| BaH2 |  |  |  | He |
| Li | Be | Ba(BO2)2Ba(BH4)2 | BaCO3BaC2O4 | Ba(CN)2Ba(N3)2Ba(NO3)2 | BaOBaO2Ba(OH)2 | BaF2BaClFBaBrF | Ne |
| Na | Mg | Ba(AlO2)2 | BaSiF6BaaCubSixOy | Ba3P2Ba3(PO4)2 | BaSBaSO3BaS2O3BaSO4 | BaCl2Ba(ClO3)2Ba(ClO4)2 | Ar |
| K | Ca | Sc | BaTiO3 | Ba(VO3)2 | BaCrO4 | BaMnO4Ba(MnO4)2 | Fe | Co | Ni | Cu | Zn | Ga | BaGeO3 | Ba3As2BaAs2 | BaSeBaSeO3BaSeO4 | BaBr2Ba(BrO3)2 | Kr |
| Rb | Sr | YBa2Cu3O7 | Zr | Nb | BaMoO4 | Tc | Ru | Rh | Pd | Ag | Cd | In | BaSnO3 | Ba3Sb2 | BaTeBaTeO3BaTeO4 | BaI2Ba(IO3)2 | Ba2XeO6 |
| Cs | Ba | 镧系 | BaHfO3 | Ta | BaWO4 | Ba(ReO4)2 | Os | Ir | BaPtBaPtCl6 | Au | Hg | Tl | Pb | Bi | Po | At | Rn |
| Fr | Ra | 锕系 | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
|  |  | ↓ |  |  |
| 镧系 | La | Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu |
| 锕系 | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |

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| 钡的有机化合物及有机酸盐
Ba(HCOO)2 · Ba(CH3COO)2 · BaC2O4 · Ba(C2H5COO)2 · Ba(PhCOO)2 · Ba(CH3C6H4SO3)2 · Ba(C17H35COO)2 |

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* 论
* 编
铜化合物 |
| --- |
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| 铜(0,I) | 
* Cu5Si

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| 铜(I) | 
* CuBr
* CuCN
* CuCl
* CuF
* CuH
* CuI
* Cu2C2
* Cu2Cr2O5
* Cu2O
* CuOH
* CuNO3
* Cu3P
* Cu2S
* CuSCN

|  |  |
| --- | --- |
| 配合物 | 
* [Cu(NH3)2]Cl
* [Cu(CH3CN)4]PF6
* [Cu(CH3CN)4]NO3]

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| 铜(I,II) | 
* Cu3H4O8S2
* C6H5Cu

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|  |
| 铜(II) | 
* Cu(BF4)2
* CuBr2
* CuC2
* CuCO3
* Cu(CN)2
* Cu(ClO3)2
* CuCl2
* CuF2
* Cu(NO3)2
* Cu3(PO4)2
* Cu(N3)2
* CuC2O4
* CuO
* CuO2
* Cu(OH)2
* CuS
* CuSO4
* Cu3(AsO4)2

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| --- | --- |
| 配合物 | 
* KCuCl3（英语：）
* [(CH3)4N]2CuCl4
* K2[Cu(C2O4)2]
* [Cu(NH3)4]SO4
* [Cu(NH3)4](NO3)2]
* [Cu(NH3)4(H2O)2](OH)2

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|  |
| 铜(III) | 
* K3CuF6
* Cu2O3

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| 铜(IV) | 
* Cs2CuF6
* Rb2CuF6
* CuO2

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