Simultaneous Cation-Substitution Effects on Superconducting Properties of Sm-Ba-Cu Oxide Superconductors

阳离子化学计量比为SMBa2Cu3O&lt；7-d&Gt；(Sm-123)为排除非化学计量比阳离子相和第二相的钉扎对J_c峰效应的贡献，合成了不同氧含量的Sm-123样品。根据拉曼散射、粉末X射线衍射仪和Rietveld分析的结果，成功地获得了阳离子化学计量比的Sm-123样品。氧含量为7-d=6.84的Sm-123样品出现了峰效应，其在77K和1T下的J_c为10kA/cm~2。另一方面，氧含量为6.89和6.95的样品没有表现出峰效应。与以往的报道相反，我们认为氧含量为6.89和6.95的样品在Sm-123超导体中出现了钉扎效应。发展了一种新的电子显微镜技术，称为大面积高分辨透射电子显微镜(LA_HRTEM)，以确定Y-Ba-Cu-O超…中峰效应的未知来源更多的传导性块头。还发展了一种用于LA-HRTEM观测中的能量色散X射线分析的样品制作方法。采用熔体生长技术，在不同氧分压下合成了Y-BaCuO超导块材。用LA-HRTEM测量了Y2BaCuO-(Y-211)粒子的晶粒度分布和孪晶界间距。在低磁场下，Y-211粒子与Y-123基体的界面面积与J_c值成正比。另一方面，在强磁场下，孪晶边界间距与J_c成反比。结果表明，孪晶界附近的贫氧区对钉扎具有峰值效应，而Y-211粒子与Y-123界面对钉扎效应的贡献很小。编制了反向出现峰值效应的热处理程序，验证了材料设计指导原则的有效性。较少

Cation-stoichiometric is SmBa_2Cu_3O_<7-d>(Sm-123) samples were synthesized to exclude contribution of pinning at particles of cation-nonstoichiometric phases and second phases to peak effect of J_c The samples were annealed in different conditions and had various oxygen contents. From results of Raman scattering, powder x-ray diffractometry and Rietveld analysis, cation-stoichiometric Sm-123 samples were successfully obtained. A Sm-123 sample with oxygen content, 7-d,=6.84 exhibited peak effect and its J_c value at 77 K and 1 T was 10kA/cm^2. On the other hand, samples with 7-d=6.89 and 6.95 did not exhibit the peak effect Contrary to the previous reports, it was concluded that oxygen depleted regions would work for the pinning to exhibit the peak effect in Sm-123 superconductors.A novel transmission electron microscopy technique termed as large area high-resolution transmission electron microscopy(LA_HRTEM) was developed to identyfy unknown origin of the peak effect in Y-Ba-Cu-O supe … More rconducting bulks. A specimen fabrication method was also developed for energy dispersive x-ray analyses in LA-HRTEM observations. Superconducting bulks of Y-Ba-Cu-O were synthesized by a melt growth technique under varied oxygen partial pressure. Distributions of grain sizes for Y_2BaCuO-(Y-211) particles and inter-twin-boundary-distances were measured utilizing LA-HRTEM. Area of the interface between the Y-211 particles and the Y-123 matrix was found to be proportional to the J_c value at low magntic fields. On the other hand, the inter-twin-boundary-distance was inversely proportional to the J_c value at high magnetic fields. From these results, oxygen depleted regions in the vicinity of the twin boundaies would work for pinning to exhibit the peak effect, while contribution of the interface between Y-211 particles and Y-123 matrix to the pinning for the appearance of the peak effect was very limited. A heat treatment program was developed to appear the peak effect reversively and confirmed the validity of the guiding principle for designing mateirals. Less