Vol.7 No.4 2015

Research paper : Preparation of superconducting films by metal organic deposition (T. MANABE et al.)−243−Synthesiology - English edition Vol.7 No.4 (2015) 4 Demonstration of YBCO thin film manufacturing and achievement of high JcIn this chapter, the outline for achieving the high Jc in Scenario I shown in Fig. 4 will be explained.4.1 Preparation of the solution and the demonstration of YBCO deposition by heat treatment in oxygenAs shown in Table 1, to achieve Goal I-1, the search for starting materials and solvents for the coating solution, the pursuit of heat treatment conditions, and the selection of low-reactive substrates were the major developmental elements.In general, the metal organic compounds with different electronegativity tend to have different solubility, and it is difficult to prepare a homogeneous solution in a multicomponent system. In this research, solvent search was conducted using the organic compounds with characteristic structures (ones with side chains or acting as ligands) as starting materials and changing the types of solvents (hydrocarbon, alcohol, acid, ketone, aldehyde, ester, and nitrogen compounds) or their chain lengths. As a result, we were able to create a coating solution in which the Y, Ba, and Cu were homogeneously dissolved in high concentration. This solution was applied to the substrate, thermally decomposed at 500 °C in an ambient atmosphere to form a prefired film composed of Y2O3-BaCO3-CuO. The final heat treatment and solid-phase reaction were done at 950 °C in oxygen as in the sintered compact, and we succeeded in demonstrating the YBCO film preparation[14][15] and obtained the basic patent for the solution and the manufacturing method. However, since the final heat treatment temperature was high, we were unable to obtain a YBCO film on the lattice-matched single-crystal substrates with a perovskite structure such as strontium titanate (SrTiO3, lattice mismatch: about 1 %) since Fig. 5 Scenario II for the manufacture of large-area superconducting film for FCLTable 1. Elemental technologies to achieve the goals in Scenario I and II for the manufacture of superconducting filmWire rodLow-oxygen low-temperature processIrradiation・thermal decomposition (ELAMOD)?Dip coating etc.Coating solution for thick films, flux pinningCeO2 vapor depositionTextured metal・Ni-W etc.1 cm widthⅡ -5:Lengthening/thickening, Achievement of high IcMicrowave filterLow-oxygen low-temperature processIrradiation・thermal decomposition (ELAMOD)Spin coatingSolution tuning[CeO2 vapor deposition]Low permittivity substrate・LAO, LSAT・sapphire2x2 cm2, 5 cmΦⅡ -4:Achievement of low Rs, patterningFCL Low-oxygen low-temperature process (large-area tubular furnace)Thermal decompositionLarge-area spin coatingSolution tuningLarge-area CeO2 vapor depositionLarge-area lattice-mismatched single crystal・sapphire・1x12 cm2, 3x21 cm2,10x30 cm2Ⅱ -3:Achievement of large-area multilayerLow-oxygen low-temperature process (tubular furnace)Thermal decompositionSpin coatingSolution tuningCeO2 vapor depositionLattice-mismatched single crystal・sapphire・2x2 cm2Ⅱ -2:Consideration of multilayer processLow-oxygen low-temperature process (infrared heating)Thermal decompositionSpin coatingSolution tuningLarge-area lattice-matched single crystal・STO,LAO・2 cmΦ, 5 cmΦⅡ-1:Primary achievement of large surface area(Josephson element)Development of low-oxygen low-temperature processThermal decompositionSpin coatingSolution tuning-Lattice-matched single crystalSTO・5x10 mm2Ⅰ -2:Achievement of high JcSearch of heat treatment condition in oxygenThermal decompositionDip coatingSearch of raw material and solvent-Selection of low-reactive substrate・YSZ・12 mmΦ, 25x25 mm2Ⅰ -1 : MOD, realization of high TcUSEFINAL HEAT TREATMENTPREFIRINGCOATINGSOLUTIONBUFFER LAYERSUBSTRATE, TYPE, SIZEGOALCore technologyUseGoalMicrowave filterFCLWire rodAchievement of low Rs and patterning Ⅱ-4Lengthening and thickening of films Ⅱ-5Manufacture of superconducting/buffer/sapphire multilayersⅡ-3Consideration of buffer/superconducting multilayering process Ⅱ-2Achievement of primary large area film on lattice-matched substrate Ⅱ-1Success of epitaxial film deposition achievement of high Jc Ⅰ-2


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