존멜팅법을 이용한 원통형 (YSmNd)-Ba-Cu-O계 초전도체의 결정성장 및 수송 전류 특성
Crystal growth and transport current properties of cylindrical (YSmNd)- Ba-Cu-O superconductors by zone melt growth method
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초록
존멜팅법을 이용해서 (YSmNd)1.8Ba2.4Cu3.4O7 − x계 고온초전도체를 대기 중에서 용융성장실험을 하였다. 존멜팅법의 최적용융온도는 1100oC였으며 성장속도는 3.5 mm/h 였다. 한 방향으로 용융성장 된 (YSN)1.8 초전도체는 XRD, 광학현미경, TEM을 이용하여 미세구조를 관찰하였으며 SQUID magnetometer와 직접전류수송법을 이용해 초전도특성을 평가하였다. 특히 용융성장 된 (YSN)1.8 초전도체의 광학현미경에 의한 미세구조 관측 결과 초전도상인 (YSN)123 matrix내에 비초전도상인 (YSN)211 inclusions이 균질하게 분포되어 있는 것이 관측되었다. 또한 용융성장 된 (YSN)1.8 초전도체는 90 K 이상의 임계온도 특성을 보였으며 액체질소 안에서 직접전류수송법으로 측정한 결과 수송전류 830 A에서 3.93 × 104(A/cm2)를 갖는 높은 임계전류밀도 특성을 보였다.
Abstract
(YSmNd)1.8Ba2.4Cu3.4O7 − x [(YSN)1.8] high Tc superconductor was directionally grown by zone melt growth process,in air atmosphere. In this study, optimum melting temperature and growth rate were 1100oC and 3.5 mm/hr, respectively. The microstructure of well-textured (YSN)1.8 samples were examined by XRD, optical microscopy, TEM and SQUID magnetometer. The critical current density of these samples were measured by the direct transporting current method. In the observation using an optical microscopy, nonsuperconducting (YSmNd)2BaCuO5[(YSN)211] inclusions of (YSN)1.8 superconductor uniformly distributed within the superconducting (YSmNd)Ba2Cu3Ox[(YSN)123] matrix. The directionally melt-textured (YSN)1.8 superconductor showed an onset Tc ≥ 90 K and sharp superconducting transition. The transport Jc values were 830 A and 3.93 × 104 (A/cm2) at 77 K self-field, respectively.
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