低氧分压区域熔炼NdBaCuO超导体

Preparation of NdBaCuO Superconductor by Zone-Melting under Low Oxygen Partial Pressure

NdBaCuO在低氧分压下(1%O2+99%Ar)进行区域熔炼,区域熔炼温度明显降低,从而减少了液相(BaCuO2和CuO)在区域熔炼过程的损失。区域熔炼后NdBaCuO超导体中的非超导相Nd422含量明显降低,同时也降低了Nd对Ba的取代。在低氧分压下区域熔炼制备的Nd1+xBa2-xCu3Oy的超导电性得到明显改善。比较了区域熔炼Nd1+xBa2-xCu3Oy样品在不同温度下吸氧热处理的实验结果,得出350℃是最佳吸氧温度;用XRD分析了区域熔炼Nd1+xBa2-xCu3Oy样品的晶体取向;用标准四引线法测量了超导转变温度(Tc)和临界电流密度(Jc),比较了空气下和(1%O2+99%Ar)低氧压下区域熔炼Nd1+xBa2-xCu3Oy样品的Nd422相含量、Tc值、Jc值,证明在(1%O2+99%Ar)低氧压下区域熔炼Nd1+xBa2-xCu3Oy样品的Nd422相含量低,Jc值显著提高,达到28000A·cm-2(0T,78K)。

When NdBaCuO superconductor samples were zonemelted in low oxygen partial pressure (1%O2+99%Ar), the zonemelting temperature is decreased obviously from that of sample melted in air. Thus the loss of liquid phase (BaCuO2 and CuO) is reduced during the zonemelting process. The content of nonsuperconducting phase Nd422 in zonemelted NdBaCuO samples is clearly decreased, in same time the substitution of Nd for Ba is decreased also. The superconductivity of zonemelted Nd1+xBa2-xCu3Oy under low oxygen partial pressure is distinctively improved. The critical current density reached 28000 A·cm-2. By comparison of the oxygenation results of the zonemelted NdBaCuO samples heattreated at different temperatures it was concluded that 350 ℃ is the optimal oxygenation temperature. The orientation and the transition temperature(Tc) as well as the critical current density(Jc) of zonemelted samples were measured and discussed. From the examination of Nd422 content of samples zonemelted both in air and in the (1%O2+99%Ar) mixture, it was found that the Nd422 content of the sample prepared in the (1%O2+99%Ar) mixture is much lower than that in sample made in air.