Study on the Improvement of Superconductor by CO_2 Laser Irradiation

用CO_2激光辐照Y-Ba-Cu-O和Bi-Sr-Ca-Cu-O超导体的结果如下：1）Y-Ba-Cu-O超导体烧结8小时的参考样品的临界温度（Tc）为90.1K。(1)超导体的临界温度通常随着烧结时间的缩短而降低。然而，在仅仅两分钟的激光照射后，可以从仅烧结一小时的材料获得92 K的最高临界温度。最佳辐照条件为激光功率40 W，扫描频率22 Hz。(2)为了提高临界电流密度，最佳辐照条件为60 W和42 Hz的扫描频率。2）Bi-Sr-Ca-Cu-O超导体对烧结50小时的参考样品（Tc=94.5 K）进行两分钟激光辐照后，发现以下结果。(1)临界温度的变化趋势与Y-Ba-Cu-O超导体相似。在激光功率为20 W、扫描频率为22 Hz的条件下，获得了102.4 K的最高临界温度。(2)临界电流密度在激光功率为80 W、扫描频率为62 Hz时出现最大值。与参比样品相比，仅在两分钟激光照射后就观察到物理性质的高度改善。(3)结果表明，在激光功率为80 W，扫描频率为62 Hz的条件下，体积分数由69.9%提高到84.3%。

Results that CO_2 laser irradiation was carried out to Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconductors are summarized as follows.1) Y-Ba-Cu-O superconductorThe critical temperature (Tc) of the reference sample which was sintered for eight hours is 90.1 K.(1) Critical temperature was generally decreased as a sintering time of the superconductor was shortened. However, after only two minutes laser irradiation, 92 K of maximum critical temperature could be obtained from the material which was sintered for only one hour. This optimized irradiation condition was found out to be 40 W of laser power and 22 Hz of scanning frequency.(2) In order to raise a critical current density, optimum irradiation condition was 60 W and 42 Hz of scanning frequency.2) Bi-Sr-Ca-Cu-O superconductorThe following results were found out after two minutes laser irradiation to the reference sample (Tc=94.5 K) which was sintered for 50 hours.(1) Critical temperature showed a similar tendency to the Y-Ba-Cu-O superconductor. 102.4 K of maximum critical temperature could be obtained in the condition of 20 W of laser power and 22 Hz of scanning frequency.(2) Critical current density showed maximum value in the 80 W of laser power and 62 Hz of scanning frequency. Comparing the reference sample, the high improvement in physical properties was observed after only two minutes laser irradiation.(3) It was confirmed that the volume percentage was improved from 69.9 % to 84.3 % in the condition of 80 W of laser power and 62 Hz of scanning frequency.