Li- and Mg-doping into Icosahedral Boron Crystals, α- and β- Rhombohedral Boron, Targeting High-Temperature Superconductivity: Structure and Electronic States
Li- and Mg-doping into Icosahedral Boron Crystals, α- and β- Rhombohedral Boron, Targeting High-Temperature Superconductivity: Structure and Electronic States
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DOI：
10.1016/j.jssc.2003.03.002
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发表时间：
2004-02
影响因子：
3.3
通讯作者：
K. Soga;Atsushi Oguri;S. Araake;M. Terauchi;A. Fujiwara;K. Kimura
中科院分区：
文献类型：
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作者：
K. Soga;Atsushi Oguri;S. Araake;M. Terauchi;A. Fujiwara;K. Kimura
对于锂和镁掺杂的二十面体硼晶体、α-和β-三方体硼晶体，提出了高TC超导电性的可能性。这些元素的掺杂是通过蒸气扩散工艺尝试的。锂和镁都很难掺杂到α-菱面体的硼中，尽管在样品中发现了少量的金属部件。只有一个Li掺杂样品的金属部分含有0.02vol%的超导相(TC∼36K)。在β-三方体硼中成功地均匀掺杂了镁，掺杂质量分数高达4AT%(镁4.1B105)，同时还引入了大量的杂质硅和镁。在镁和硅共掺杂的情况下，对掺杂样品的结构进行了分析。讨论了掺杂物的晶位占有率与晶格膨胀的关系。由EELS和磁化率测量估算的费米能级附近的态密度表明，镁和硅的掺杂使β-三方体硼发生了金属相变。讨论了金属跃迁与本征受主能级的关系。
The possibility of high TCsuperconductivity is suggested for lithium- and magnesium-doped icosahedral boron crystals, α- and β-rhombohedral boron. The doping of these elements was attempted by a vapor diffusion processing. Both lithium and magnesium are hardly doped into the α-rhombohedral boron, although small amounts of metallic parts are found in the sample. In only one Li-doped sample, the metallic part contained 0.02vol% of the superconductive phase (TC∼36K). Magnesium was successfully doped into β-rhombohedral boron homogeneously up to 4at% (Mg4.1B105), although considerable amount of impurity silicon was introduced together with magnesium. The structures of the doped samples were analyzed assuming co-doping of magnesium and silicon. The relation between the site occupancies of the dopants and the lattice expansion is discussed. The estimation of the density of states near the Fermi energy by EELS and magnetic susceptibility measurements suggested a metal transition of the β-rhombohedral boron by the doping of magnesium and silicon. The relation between the metal transition and the intrinsic acceptor level is also discussed.