Epitaxial Growth of Yb 2 O 3 Buffer Layers on Biaxially Textured-Ni (100) Substrates by Sol-Gel Process
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The process involves
obtaining cube textured Ni (100) substrates by cold-rolling Ni rods followed by recrystallization. The buffer layers are then epitaxially grown on the textured metal substrates followed by the deposition of in-plane oriented superconducting films. Critical current densities of YBCO films over 1 MA/cm 2 at 77 K have been demonstrated on rare-earth oxide (RE 20 3) buffer layers with various architectures via vacuum process [3,4]. The goal of this research is to develop the RABiTS process using a non-vacuum approach such as the sol-gel or the MOD processes. The non-vacuum approach has many advantages. The techniques are very cost-effective and easily scalable. The solution process gives better homogeneity and composition control because the precursors are mixed at atomic levels. Substrates with various shapes and forms can be coated with ease by spin coating or dip coating methods. Previously, buffer layers prepared by the sol-gel technique showed epitaxial growth on single crystal substrates [5-9], but resulted in multiple orientations on textured-Ni (100) substrates [10-12]. Beach et al. at ORNL recently demonstrated the epitaxial growth of a rareearth oxide, Gd 20 3, buffer layer on textured-Ni (100) substrate by sol-gel process for the first time [13]. The Gd2 0 3 precursor solution was prepared via an all alkoxide sol-gel route. The textured film had a continuous and a dense microstructure without any cracks. In this paper, we report the preparation of the Yb 20 3 precursor solution, film deposition and characterization of the sol-gel buffer layer on textured-Ni (100) substrate for the first time.
51 Mat. Res. Soc. Symp. Proc. Vol. 574 © 1999 Materials Research Society
We also demonstrate the deposition of a high J, YBCO film on a sol-gel grown buffer layer with sputtered cap layers, YSZ and CeO 2 . EXPERIMENTAL The solution preparation was carried out under an Ar atmosphere using a Schlenck-type apparatus. The isopropanol was dried by distillation from aluminum isopropoxide. The ytterbium ingot and 2-methoxy ethanol (Alfa) were used without further purification. The flow chart for the ytterbium precursor preparation is shown in Figure 1. The first step involved the preparation of ytterbium isopropoxide from ytterbium metal. This was achieved by reacting the ytterbium metal filings with dry isopropanol in the presence of mercuric catalyst. The ytterbium isopropoxide was extracted using a Soxhlet extractor with isopropanol and recrystallized to obtain a highly pure final product. The second step involved the exchange of the isopropoxide ligand for a methoxyethoxide
ligand. About 1.66g (6.25 minoles) of ytterbium isopropoxide was weighed out in a 200 ml round bottom flask and dissolved in 50 ml of 2-methoxyethanol. After the solution was refluxed for one hour, approximately 30 ml of the isopropanol and 2-methoxy ethanol solvent mixture was removed by distillation. The solution was rediluted with 2-methoxyethanol and distilled repeatedly to ensure complete ligand exchange. Finally, the volu
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