Upper critical field, irreversibility field, and critical current density of powder-in-tube-processed MgB2/Fe tapes
Upper critical field, irreversibility field, and critical current density of powder-in-tube-processed MgB2/Fe tapes
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DOI：
10.1088/0953-2048/18/8/003
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发表时间：
2005-08
影响因子：
3.6
通讯作者：
H. Kumakura;H. Kitaguchi;A. Matsumoto;H. Yamada
中科院分区：
文献类型：
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作者：
H. Kumakura;H. Kitaguchi;A. Matsumoto;H. Yamada
我们以MgH 2为原料，在600-900 °C的温度下进行热处理，制备了纯MgB 2和添加SiC的MgB 2/Fe复合带材，并系统地研究了它们的超导性能。对于纯带和添加SiC的带，由于MgB 2结晶度的提高，临界温度（Tc）随热处理温度的升高而升高。SiC的添加降低了Tc，但增加了所有热处理温度下Bc 2-T和Birr-T曲线的斜率d Bc 2/dT和d Birr/dT。纯带的d Bc 2/dT和d Birr/dT随着热处理温度从600 ° C增加到700 °C而减小，这是因为与改善的结晶度相关的较长的相干长度。然而，SiC的加入显著降低了dBc 2/dT和dBirr/dT的热处理温度依赖性。在使用低温冷却器很容易获得的20 K的温度下，Birr由Tc和d Birr/dT两者控制。纯带材在20 K下的Birr随着热处理温度从600 °C增加到700 °C而降低，但添加10 mol% SiC的带材的Birr随着温度而增加。这些行为可以通过Tc和dBirr/dT的热处理温度依赖性来解释。在20 K下，当SiC添加量为10 mol%，热处理温度为900 °C时，获得了10 T的最高Birr。该在20 K下的Birr与商业Nb-Ti在4.2 K下的Birr相当。在900 °C下热处理的添加有10摩尔% SiC的带和在5at.在800 °C下热处理的添加SiC的带在20 K和5 T下显示出高于104 A cm−2的Jc（MgB 2芯）值。
We fabricated pure and SiC-added MgB2/Fe composite tapes using a MgH2 starting powder and applying heat treatments at 600–900 °C and systematically investigated their superconducting properties. For both the pure and SiC-added tapes, the critical temperature (Tc) increased with increasing heat-treatment temperature due to the improved crystallinity of MgB2.The SiC addition decreased the Tc but increased the slope of the Bc2–T and Birr–T curves, d Bc2/d T and d Birr/d T, for all heat-treatment temperatures. The d Bc2/d T and d Birr/d T of the pure tape decreased with increasing heat-treatment temperature from 600 to 700 °C because of the longer coherence length associated with the improved crystallinity. However, the SiC addition significantly decreased the heat-treatment temperature dependences of d Bc2/d T and d Birr/d T. At a temperature of ∼20 K, which is easily obtained using a cryocooler, the Birr is governed by both the Tc and d Birr/d T. The Birr of a pure tape at 20 K decreased with increasing heat-treatment temperature from 600 to 700 °C, but the Birr of the 10 mol% SiC-added tape increased with the temperature. These behaviours can be explained by the heat-treatment temperature dependence of the Tc and d Birr/d T. At 20 K the highest Birr of 10 T was obtained under the conditions of a 10 mol% SiC addition and heat-treatment temperature of 900 °C. This Birr at 20 K is comparable to that of commercial Nb–Ti at 4.2 K. The 10 mol% SiC-added tape heat treated at 900 °C and the 5 at.% SiC-added tape heat treated at 800 °C showed Jc (MgB2 core) values higher than 104 A cm−2 at 20 K in 5 T.