Zhang Yun, Lu Cheng, Zhou Sihai, Joo Jinho
Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Ave., Wollongong, NSW 2522, Australia.
J Nanosci Nanotechnol. 2009 Dec;9(12):7402-6. doi: 10.1166/jnn.2009.1764.
In this report, high-purity nanocrystalline boron powders processed by ball-milling were used as the precursor powders to fabricate MgB2 superconductor. The transport properties and the critical current density in the samples made from ball-milled boron powders and as-supplied boron powders were investigated. It was found that the ball-milled boron powders led to a significant enhancement of the critical current density in MgB2 sintered at 650 degrees C. The reason can be attributed to the small MgB2 grain size caused by the ball-milled boron precursor powders. The resistivity of the samples made from the ball-milled boron powder was lower than that of the sample from as-supplied boron powder. As the sintering temperature increased, both resistivity and upper critical field decreased in the samples using the ball-milled boron powders as a precursor. Poor connectivity and large strain are responsible for the high resistivity.
在本报告中，通过球磨处理的高纯度纳米晶硼粉被用作前驱体粉末来制备MgB₂超导体。研究了由球磨硼粉和供应态硼粉制成的样品的输运性质和临界电流密度。结果发现，球磨硼粉使在650℃烧结的MgB₂中的临界电流密度显著提高。原因可归因于球磨硼前驱体粉末导致的MgB₂晶粒尺寸较小。由球磨硼粉制成的样品的电阻率低于由供应态硼粉制成的样品。随着烧结温度升高，以前驱体使用球磨硼粉的样品的电阻率和上临界场均降低。连通性差和应变大是导致高电阻率的原因。
