论文部分内容阅读
1973年以来,对高温超导电性的研究几乎停顿不前.Bednorz和Mulle在La—Ba—Cu—O系中高于30K超导电性的发现迅速改变了这种局面。以后的发展近乎日新月异。赵忠贤等首先报道了在Y—Ba—Cu—O体系中发现高于液氮温度(77K)的超导电性并公布了材料组分。接着C.W.Chu等在Y—Ba—Cu—O多相氧化物超导体中得到了高于90K的的超导电性。最近,更多的研究组在单相YBa_2Cu_3O_(9~-y)氧化物超导体中发现了高于90K超导电性。我们在研制单相YBa_2Cu_2O_(9~-y)超导材料过程中发现,制备条件对超导性质的影响很大。我们选用分析纯钇钡铜的氧化物或碳酸盐。阳离子配比为Y∶B∶Cu=1∶2∶3。在玛瑙研钵里充分研磨以后,在管式炉内900—1100℃通氧烧结12—24小时。冷却速率对超导性质的影响是显著的。缓慢(超过6小时)冷却到室温可得到零电阻温度高于90K的超导电性,如图1所示。快速冷却的零电阻温度低于77K,如图2所
The study of high-temperature superconductivity has been almost at a standstill since 1973. The discovery that Bednorz and Mulle exceed 30K in the La-Ba-Cu-O system has rapidly changed this situation. After the development of almost ever-changing. Zhao Zhongxian first reported in the Y-Ba-Cu-O system found higher than the liquid nitrogen temperature (77K) superconductivity and published the material composition. Then C. W. Chu et al. Obtained superconductivity above 90 K in Y-Ba-Cu-O multi-phase oxide superconductors. More recently, more groups have found superconductivity above 90K in single-phase YBa2Cu3O9 (9-y) oxide superconductors. We found in the development of single-phase YBa_2Cu_2O_ (9 ~ -y) superconducting materials found that the preparation conditions have a great influence on the superconductivity properties. We choose to analyze the oxide or carbonate of yttrium barium copper. The cation ratio is Y: B: Cu = 1: 2: 3. After grinding thoroughly in an agate mortar, oxygen is sintered at 900-1100 ° C for 12-24 hours in a tube furnace. The effect of cooling rate on superconducting properties is significant. Slow (more than 6 hours) cooling to room temperature can be zero-resistance temperature higher than 90K superconductivity, as shown in Figure 1. Rapid cooling of the zero-resistance temperature below 77K, as shown in Figure 2