Journal of the Korean Crystal Growth and Crystal Technology (한국결정성장학회지)

The Korea Association of Crystal Growth (한국결정성장학회)
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Melt growth and superconducting properties of Sm-doped YBCO super-conductor by zone melting method

국부용융성장법으로 제조된 Sm이 첨가된 YBCO 초전도체의 용융온도 및 성장 속도에 따른 미세구조

  • 김소정 (동해대학교 전기전자공학과)
  • Published : 2004.04.01
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Abstract

Sm-doped YBCO high $T_c$ superconductor was directionally grown by zone melt growth process in air atmosphere. Cylindrical green rods of $(Sm/Y)_{1.8}Ba_{2.4}Cu_{3.4}O_{7-x}$[(Sm/Y)1.8] oxides were fabricated by cold isostatic pressing (CIP) method using rubber mold. Based on the variation of melting temperature and growth rate, the microstructure and superconducting properties were systematically measured by using optical micrographs, TEM and SQUID magnetometer. In this study optimum melting temperature and growth rate were $1085^{\circ}C$ and 3.5 mm/hr respectively. Nonsuperconducting $(Sm/Y)_2BaCuO_5$ inclusions of (Sm/Y)1.8 superconductor were uniformly distributed within the superconducting (Sm/Y) $Ba_2Cu_3O^{7-x}$ matrix. The directionally melt-textured (Sm/Y)1.8 superconductor showed an onset $T_c$ $\geq$ 90K and sharp superconducting transition.

Sm 원소가 첨가된 $(Sm/Y)_{1.8}Ba_{2.4}Cu_{3.4}O_{7-x}$[이하 (Sm/Y)1.8] 고온초전도체를 국부용융성장법을 이용해 대기 중에서 용융성장실험을 하였다. 초기 (Sm/Y)1.8 초전도체 시편은 rubber 몰드를 이용해 냉간정수압성형(CIP) 과정을 거쳐 길이 방향 원통형상으로 제조되었다. 이렇게 얻어진 (Sm/Y)1.8 초전도체는 용융온도 및 성장속도에 따라 광학현미경, TEM그리고 SQUID magnetometer를 이용해 미세구조 및 초전도특성을 평가하였다. 이 결과 (Sm/Y)1.8 초전도체의 최적의 용융온도 및 성장속도는 $1085^{\circ}C$에서 3.5mm/hr로 나타났다. 특히 일방향으로 용융성장된 (Sm/Y)1.8 초전도체의 광학현미경 및 TEM에 의하 미세구조 관측 결과, 초전도상인 (Sm/Y)123 matrix내에 비초전도상인 (Sm/Y)211 inclusions이 균질하게 분포되어 있는 것이 관측되었다. 초전도특성을 평가한 결과 용융성장된 (Sm/Y)1.8초전도체는 90K에서 임계온도가 시작되어 77K이상의 온도에서 포화되는 특성을 보였다.

Keywords

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