SUPERCONDUCTIVITY IN THE QUATERNARY INTERMETALLIC COMPOUNDS LNNI2B2C
SUPERCONDUCTIVITY IN THE QUATERNARY INTERMETALLIC COMPOUNDS LNNI2B2C
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DOI：
10.1038/367252a0
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发表时间：
1994-01-20
期刊：
影响因子：
64.8
通讯作者：
UCHIDA, S
中科院分区：
文献类型：
--
作者：
CAVA, RJ;TAKAGI, H;UCHIDA, S
氧化铜超导体达到前所未有的高转变温度（T（c）s）说明了如何与更复杂的化学系统一起工作，从而有更多机会平衡单一化合物内的相反力，从而更好地优化物理性能。对于许多理想的性质来说，具有最佳化学复杂性的材料无疑还没有被发现，这似乎是金属间化合物超导体的情况，近年来对它的研究已经停滞，并且几乎从未显示出高于15 K的T（c）。这些化合物几乎都是含有取代型添加剂的二元化合物，或者很少是真正的三元化合物，如LuRh 4 B4（T（c）= 11.7 K;参考文献1，2）。如果像某些人所争论的那样（参考文献3、4），诸如A（x）C60（参考文献5）和Ba 0.6K 0.4Bi O3（参考文献6、7）等材料是T（c）s约为30 K的传统电子-声子超导体，那么金属间化合物中没有更高的T（c）s可能仅仅意味着更复杂的材料还没有得到充分的探索。我们最近在钇-钯-硼-碳四元金属间化合物系统中发现了23 K时的超导性（a T（c）等于先前金属间化合物记录保持器Nb 3Ge的T（c）;参考文献9），但我们无法确定超导相。在这里，我们报告超导温度高达16.6 K的单相四元金属间化合物LnNi 2B 2C（其中Ln代表Y，Tm，Er，Ho或Lu）。 3d过渡金属镍的存在和层状晶体结构10提出了关于超导性起源的有趣问题，这些和Y-Pd-B-C超导体相对较高的T（c）表明可能还有更多的惊喜。
THE attainment of unprecedentedly high transition temperatures (T(c)s) in the copper oxide superconductors illustrates how working with more complex chemical systems allows greater opportunity to balance opposing forces within a single chemical compound, leading to a better optimization of physical properties. For many desired properties, materials with optimal chemical complexity have undoubtedly not yet been found. This appears to be the case for the intermetallic superconductors, whose study has languished in recent years, and which almost never show T(c)s above 15 K. These are almost all binary compounds with substitution-type additives, or, rarely, true ternary compounds such as LuRh4B4 (T(c) = 11.7 K; refs 1, 2). If, as some argue (refs 3, 4), materials such as A(x)C60 (ref. 5) and Ba0.6K0.4BiO3 (refs 6, 7) are conventional electron-phonon superconductors with T(c)s of approximately 30 K, then the absence of higher T(c)s in intermetallic compounds may mean only that more complex materials have not been sufficiently explored. We have recently found superconductivity at 23 K (a T(c) equal to that of the previous intermetallic record holder, Nb3Ge; ref. 9) in the quaternary intermetallic system yttrium-palladium-boron-carbon8, but we were unable to identify the superconducting phase. Here we report superconductivity at temperatures up to 16.6 K for the single-phase quaternary intermetallic compounds LnNi2B2C (where Ln stands for Y, Tm, Er, Ho or Lu). The presence of the 3d transition metal nickel, and the layered crystal structure10 raise intriguing questions about the origin of the superconductivity, and the relatively high T(c)s of these and the Y-Pd-B-C superconductor suggest that there may yet be more surprises in store.