Essential factors for the critical current density in superconducting MgB2:: connectivity and flux pinning by grain boundaries
Essential factors for the critical current density in superconducting MgB2:: connectivity and flux pinning by grain boundaries
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DOI：
10.1088/0953-2048/21/01/015008
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发表时间：
2008-01-01
影响因子：
3.6
通讯作者：
Kishio, Kohji
中科院分区：
文献类型：
--
作者：
Matsushita, Teruo;Kiuchi, Masaru;Kishio, Kohji
电学连通性和晶界磁钉强度是决定超导多晶MgB2临界电流密度的重要因素。对不同制备方法制备的MgB2散装样品进行了定量研究。利用渗流模型对电连通性进行了评价，并将得到的电连通性用于估计超导MgB2晶粒的剩余电阻率。利用Yetter等人基于残余电阻率的电子散射机制的理论结果，对晶界的基本钉住力进行了计算。结果表明，临界电流密度与电连度、晶界的基本钉住力和晶粒尺寸的倒数近似成正比。这证实了临界电流密度主要由电连通性和晶界的磁钉强度决定。比较了MgB2与Nb3Sn在完全电连通性条件下的磁链钉接性能。结果表明，纯MgB2的通量钉钉能力与Nb3Sn相当甚至更高，表明掺杂碳的MgB2具有更高的潜力。这证明了MgB2是一种有实际应用前景的超导体。
Electrical connectivity and flux pinning strength of grain boundaries are essential factors in determining the critical current density in superconducting polycrystalline MgB2. The effect of these factors is quantitatively investigated for a series of MgB2 bulk samples prepared by various methods. The electrical connectivity is evaluated using the percolation model and the obtained electrical connectivity is used for the estimation of the residual resistivity of superconducting MgB2 grains. The elementary pinning force of grain boundaries is evaluated using the theoretical result of Yetter et al based on the electron scattering mechanism with the residual resistivity. It is found that the critical current density is approximately proportional to the product of the electrical connectivity, the elementary pinning force of grain boundaries and the reciprocal grain size. This confirms that the critical current density is dominantly determined by the electrical connectivity and the flux pinning strength of grain boundaries. The flux pinning property in MgB2 under the condition of full electrical connectivity is compared with that in Nb3Sn. The obtained result shows that the flux pinning ability of pure MgB2 is comparable to or even higher than that of Nb3Sn, indicating a much higher potential in carbon-doped MgB2. This proves that the MgB2 is a promising superconductor for practical applications.