Syntheses of YSr2Cu3(1-a)Mo3aOy and LaBa2Cu3Oy High-Tc Superconductor and the Effects of Heat-Treatment on Their Structures and Superconductvities

• Main Authors: Wu, Ma-Shine, 吳銘訓
• Other Authors: Tsang-Tse Fang
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/22000579888932895901

博士 === 國立成功大學 === 材料科學(工程)學系 === 86 === In this study, the citrate gel pyrolysis process was used to synthesize the LaBa2Cu3Oy and YSr2Cu3(1-a)Mo3aOy superconducting powders. Phase evolution and the relationships among oxygen content, structure and superconductivities during calcination and heating treatment were investigated, which would lend support to pursue the formation mechanisms of LaBa2Cu3Oy and YSr2Cu3(1-a)Mo3aOy superconductors and the effects of annealing on their structures and superconductivities. It was found that the mechanism for producing a single-phase LaBa2Cu3Oy in an inert atmosphere at a higher temperature is to remove oxygen and lengthen the c axis, which in turn would make the La and Ba in order. A single-phase LaBa2Cu3Oy could be achieved by heating the specimen at the temperature 950℃ in Po2= 0.0002atm. The precursor (Sr1-xYx)14Cu24O41plays a crucial role in forming the YSr2Cu3(1-a)Mo3aOy superconductor. It was shown that the stablization of YSCO superconductor was via the reaction of Mo6+ ion with the (Sr1-xYx)14Cu24O41. The Tconset=40K for YSr2Cu3(1- a)Mo3aOy could be obtained by heating at 1000℃ in O2 atmosphere and annealing at600℃ in O2 atmosphere. The superconductivity of LaBa2Cu3Oy could reachTconset=93K and Tcoffset=88K by heating at 700℃ in Po2=0.01 atm for 6h andannealing at 300℃ in O2 for 24h.The mechanisms of the anomaly in the c axisand orthorhombic- tetragonal transition have been proposed.