To study the crystal and the bulk in a Ru-based Double Perovskite compound Ba2YRu1-xCuxO6

• Main Authors: Ting-Rong Chen, 陳亭蓉
• Other Authors: Maw-Kuen Wu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/08690196924498820579

碩士 === 國立清華大學 === 物理學系 === 93 === In order to classify the superconducting phase within Ba2YRu1-xCuxO6 (BaY2116) system, both BaY2116 crystals and bulks have been prepared and investigated. Crystals were grown in a homemade furnace with PbO+PbF2 flux, that is a high temperature solution growth technique, and bulks were prepared by a typical solid state reaction Crystals were grown from 1120℃ to 1100℃ by a cooling rate 0.2℃~0.5℃ per hour, where bulks were sintered in air at 1460℃~1485℃ for 2 hours. XRD, SQUID, SEM/EDS and EPMA were performed on these two kinds of samples. Bulks were further examined by R-T and TEM to obtain more information about electrical properties and nanostructure. The EDS mapping of the crystal surface showed that Cu and Ru can not coexist in the same region, and it also contained PbO precipitation. Some region only had Y, Ba, Cu, and O. Inside the crystal, the Ba3YRu2O9 was surrounded by Ba2YRuO6 and accompanied with Pt and Cu precipitations. The diamagnetic signal was eliminated after polishing the surface. All these results showed that crystals were actually polycrystalline samples, and the superconducting phase was only exist on the surface. For bulks an unwanted YBa2Cu3O7 (Y123) phase can be detected in all superconducting samples. The diamagnetic intensity per unit volume was proportional to the relative XRD peak intensity. For lower Cu doped bulks (x<0.3) sintered in a higher temperature or for a longer duration would lead more Y2O3 or Y123, but repeat sintering would reduced these undesired phases. On the contrary, more sintering times would cause more Y123 or Y2O3 phase for those higher doped bulks.