Vol.7 No.4 2015

Research paper−239−Synthesiology - English edition Vol.7 No.4 pp.239-250 (Mar. 2015) high-volume interconnection of distributed power supply sites using low-cost superconducting film. 1.2 Metal organic deposition (MOD) methodThe authors had been engaging in the development of ceramic thin film manufacturing process by the metal organic deposition (MOD) method before the discovery of high-temperature superconductors. MOD is a method of “coating and firing” where the metal organic compound containing the constituent elements are dissolved in an organic solvent, this solution is coated onto a substrate, and heat treatment is done to burn off the organic components to form the metal oxide film (Fig. 3).[3][4]Since the MOD method is comprised of simple processes of “coating and firing” and does not require a large-scale device that produces high vacuum or high voltage, it has the following characteristics: (1) it is easy to accurately control the chemical composition of the film, (2) it uses relatively low temperature in the process, (3) it can be applied to large surface area substrates of various forms as well as tapes of long length, and (4) it has low environmental load since it emits only steam and carbon dioxide during complete combustion and does not emit harmful substances such as hydrogen fluoride as in the MOD method that uses metal trifluoroacetates as a raw material (TFA-MOD).[5]This paper describes the approaches and methods that were employed to achieve the goal for meeting the product requirement. The technology was developed to create a high-1 Background of the research1.1 High-temperature oxide superconductor and its application to a fault current limiter (FCL)The high-temperature oxide superconductor that was discovered in 1986 was later found that its critical temperature (temperature at which superconductive condition is achieved and the electrical resistance is zero: Tc) can be increased to 90 K with the discovery of perovskite-type compound YBa2Cu3O7 (hereinafter will be called YBCO), and the expectation for its practical application rose since it can be used with low-cost liquid nitrogen (boiling point 77 K) instead of expensive liquid helium (boiling point 4 K). For example, if this material is processed into power transmission cables, the loss due to resistance during power transmission can be reduced, and it was calculated that the transmission loss can be kept at about half compared to copper wire even considering the energy needed for cooling.[1]Various applications and devices, not just power transmission cables, can be realized by processing the superconductor into thin film form. One such device is the SN transition type (thin film type) fault current limiter (FCL). As it will be explained in chapter 2, FCL is a new kind of electrical device that instantly inhibits large overcurrent that may occur due to lightning strikes or tree falls on the transmission or distribution lines, thus facilitating the shutoff of accidental current (Fig. 1).[1][2] Since the thin film type FCL (Fig. 2) is highly reliable and is capable of handling high voltage and large current, there is expectation for development toward - Research and development towards a fault current limiter and other electric devices-For the application of oxide superconductors to power-electric and microwave devices, it is necessary to form oxide superconductors into films and tapes. Since oxide superconductors are fragile and processing resistant, establishing a thin film processing technology for oxide superconductors is important. In this article, we describe our approach to developing such technology with an example that involves the processing of high quality large-size superconducting thin films by metal organic deposition (MOD) for the realization of a fault current limiter. MOD is a simple and low-cost processing technology for metal oxide thin films, which are prepared by dipping a substrate in a coating solution and firing the substrate. Preparation of superconducting films by metal organic depositionKeywords : Metal organic deposition, superconductor, thin films, fault current limiter, microwave devices, coated conductor [Translation from Synthesiology, Vol.7, No.4, p.247-257 (2014)]Takaaki Manabe*, Mitsugu Sohma, Iwao Yamaguchi, Hiroaki Matsui, Tetsuo Tsuchiya and Toshiya KumagaiAdvanced Manufacturing Research Institute, AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba 305-8565, Japan*E-mail: Original manuscript received June 6, 2014, Revisions received July 25, 2014, Accepted August 11, 2014


page 43