Engineered oxide thin films as 100%lattice match buffer layers for YBCO coated conductors

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• 作者：Akin ; Y. ; Heiba ; Z.K. ; Sigmund ; W. ; Hascicek ; Y.S.
• 关键词：Buffer layers ; YBCO ; Eu₂O₃ ; Yb₂O₃ ; Lattice parameter ; Sol&ndash ; gel
• 刊名：Solid-State Electronics
• 出版年：2003
• 期刊代码：73_00381101
• 类别：ph
• 出版时间：December, 2003
• 卷：47
• 期：12
• 页码：2171-2175
• 文件大小：437 K

摘要

One of the most important qualities of buffer layers for RE-BCO coated conductors’ growth is close lattice match with RE-BCO. However, there is no natural material with a 100%lattice match with RE-BCO. In this study mixtures of europium oxide (Eu₂O₃) and ytterbium oxide (Yb₂O₃), (Eu_1−uYb_u)₂O₃ (0.0≤u≤1.0), were investigated as a candidate buffer layer that could have same lattice parameter as YBa₂Cu₃O_7−δ(YBCO). Because the pseudocubic lattice parameter of Eu₂O₃ is bigger, and that of Yb₂O₃ is smaller than lattice parameter of YBCO, and the mixed oxides with appropriate ratio would have same lattice parameter of YBCO. The mixtures were prepared using metal-organic precursor by sol–gel process, and it was found that all mixed samples are single phase, complete solid solutions, and have same crystal system over the whole range of “u”. Lattice parameters of mixed (Eu_1−uYb_u)₂O₃ oxide powders were changed between 10.86831 and 10.42828 Å which are lattice parameter of Eu₂O₃ and Yb₂O₃, respectively by changing the ratio of Eu/Yb in the mixture. Phase and lattice parameter analysis revealed that pseudocubic lattice parameter of (Eu_0.893Yb_0.107)₂O₃ is 3.82 Å which is same as the lattice parameter of YBCO. Textured (Eu_0.893Yb_0.107)₂O₃ buffer layers were grown on biaxially textured-Ni (100) substrates. The solution was prepared from Europium and Ytterbium 2,4-pentadioanate, and was deposited on the Ni substrates using a reel-to-reel sol–gel dip coating system. The textured films were annealed at 1150 °C for 10 min under 4%H₂–Ar gas flow. Extensive texture analysis has been done to characterize the texture of (Eu_0.893Yb_0.107)₂O₃ buffer layers. X-ray diffraction (XRD) of the buffer layer showed strong out-of-plane orientation on Ni tape. The (Eu_0.893Yb_0.107)₂O₃ (222) pole figure indicated a single cube-on-cube textured structure. The omega and phi scans revealed good out-of-plane and in-plane alignments. The full-width-at-half-maximum (FWHM) values of omega and Phi scan of (Eu_0.893Yb_0.107)₂O₃ films were 6.45° and 7.70°, respectively. ESEM micrographs of the films revealed pinhole-free, crack-free and dense microstructures.