Vol.7 No.4 2015

Research paper : Preparation of superconducting films by metal organic deposition (T. MANABE et al.)−246−Synthesiology - English edition Vol.7 No.4 (2015) temperature high, we obtained a CeO2 film with a large surface that was smooth and uniform at nanometer level.[28][29]We introduced a spin coater to handle large substrates for the large-area YBCO deposition, and a coating solution that was tuned for viscosity and evaporation rate to ensure even film thickness was applied. Next, in the prefiring process, totally uniform prefired film was obtained using a large muffle or tubular furnace in which the heating rate and the atmosphere were controlled. From the result of subchapter 5.2, it became apparent that rapid heating using the infrared image furnace was not necessary for the final heat treatment, and we succeeded in manufacturing a high-performance YBCO film on a large-area sapphire substrate of 10 cm × 30 cm size, by conducting precise temperature and atmosphere control using a large tubular furnace with high temperature uniformity (Fig. 7). It was on average Jc = 2.6 MA/cm2 as obtained in the inductive method, and the uniformity of average Jc within ±20 % range was obtained for the majority of the measurement points. The goal value of the project in chapter 2 was achieved (II-3).[31]-[33]6 Later developmentUp to the previous chapter, we described the development of the synthesis technology of the large-area superconducting film by the MOD method. In this chapter, we shall discuss the later development: (1) the result of manufacturing the fault current limiting element using the superconducting film developed in this research, in a joint research with external institutions (companies, universities, and the Central Research Institute of Electric Power Industry) and a research group within AIST (jointly with Energy Technology Research Institute), and then creating a prototype FCL by a series-parallel arrangement and conducting the current limiting test; and (2) the application to microwave devices and wire rods. Please refer to the references for details.6.1 Prototype FCL testThe superconducting films for the element were prepared by depositing on the CeO2/sapphire substrate of 3 cm × 21 cm size with high throughput and uniformity, and a gold-silver alloy shunt layer with high resistance was formed to increase the voltage produced after quenching.[34](1) Joint research: mockup device (Fig. 8)The 6.6 kV class single-phase FCL unit, in which six units of two parallel elements were connected in series, was used to limit the peak current of 11.3 kA to 4.5 kA. Based on this result, conceptual design of the 6.6 kV class triple-phase FCL was done.[35](2) AIST research:The 500 V/200 A single-phase FCL unit that used the non-inductive shunt resistance developed by AIST was used to limit the peak current of 3.5 kA to 770 A.[36]The cost of the large-area superconducting film used for FCL in the dispersed distributed power supply site was calculated, and it was shown that in the future it will be lower than the target cost of realization.[37]Based on these results, the technological transfer to companies of the large-area superconducting film manufacturing process is being promoted.6.2 Application to microwave devices and wire rods and tapes(1) Microwave filter for mobile communication base stationSince the high-temperature superconductor has lower surface resistance than metal in the microwave range, call-enabled areas can be expanded and effect of electromagnetic wave can be decreased by increasing the communication quality by incorporating a filter made from a superconducting film into the mobile communication base station system.[38][39] Here, the goals (II-4) required for the superconducting film are double-sided deposition on a large-area (5 cm in diameter), low-permittivity substrate, low surface resistance, and patterning. The authors obtained the following results for the application to this field. Fig. 7 Large-area YBCO films manufactured on substrates of various formsFig. 8 6.6 kV single-phase FCL prototype


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