The introduction of effective artificial pinning centers into pulsed laser deposition derived Gd 1 Ba 2 Cu 3 O 7−δ coated conductors has been studied with a view to improving the I c -B-θ properties. BaMO x (M = metal) was introduced into Gd 1 Ba 2 Cu 3 O 7−δ film, with the expectation of forming fine nanorods such as BaZrO 3 ones. BaHfO 3 doped Gd 1 Ba 2 Cu 3 O 7−δ coated conductors showed remarkably good I c -B-θ characteristics, even at high temperature. A short sample with 1 µm film thickness prepared using a reel-to-reel system showed a minimum I c value of 30 A/cm-w@77 K (A/cm-w@77 K to be read as 'amps per centimeter width, at 77 K') at 3 T. The minimum J c value of ∼0.3 MA cm −2 @77 K at 3 T was independent of the film thickness up to 2.9 µm. The 2.9 µm thick film showed a minimum I c value of 84.

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Double artificial pinning centers of BaSnO 3 nanorods and Y 2 O 3 nanoparticles were investigated in YBa 2 Cu 3 O 7 films on textured substrates prepared using ion beam assisted deposition. The BaSnO 3 and Y 2 O 3 content was varied in pulsed laser deposition. Transmission electron microscopy observation revealed the systematic change in density of the BaSnO 3 nanorods and the Y 2 O 3 nanoparticles in the films. In YBa 2 Cu 3 O 7 + BaSnO 3 films, maximum global pinning force (F p,max ) was improved at high magnetic fields, and F p,max was shifted to high magnetic field by the Y 2 O 3 incorporation due to an increase in density of the pinning centers. The angular dependences of critical current density (J c ) in the YBCO + BaSnO 3 films were tuned by introducing Y 2 O 3 , and some of the YBa 2 Cu 3 O 7 + BaSnO 3 + Y 2 O 3 films exhibited isotropic J c behavior at low magnetic field. The double artificial pinning centers of BaSnO 3 nanorods and Y 2 O 3 nanoparticles are effective in improving J c angular dependences, J c values at high magnetic fields, and F p,max .

The current national project on coated conductors using Y-system superconductors has been carried out over the project period (FY2003–FY2007). In this paper, the current status and the future prospect of this project are reviewed. The high performance tape development group, consisting of Fujikura and SRL-NCCC, has worked on the tape by PLD-REBCO superconducting layers on PLD-CeO2/IBAD-GZO buffered substrates. A high product of Ic and L, higher than 112 166 A m, was achieved in a 368 m–304.8 A GdBCO tape whose Ic value is mostly above 350 A/cm in width. The performance under magnetic field was also improved up to 42 A at 3 T in a GdBCO short film with doping of ZrO2. 61 m long GdBCO tape with ZrO2 doping showed a high Ic value of 220 A at self field and 30 A at 3 T. On the other hand, another group focusing on low production cost has worked on TFA-MOD and MOCVD processes. The extremely high Ic value of 735 A/cm-w was obtained in TFA-MOD films on PLD-CeO2/IBAD-GZO/Hastelloy substrate due to the effect of Ba-poor nominal composition. In efforts towards long tape production by the SWCC group, a 200 m long tape with a high Ic value of 200 A/cm-w was obtained using a batch-type furnace. The Ic × L value of this tape was 40 000 A m, which is the highest value in the world obtained by the TFA-MOD process. Based on the above achievements in coated conductor process development, two new additional goals were set in the project. One is the development of extremely low cost tape and the other is the development of the basic technologies for making electric power devices of cables, transformers, motors, current-limiters and cryocoolers. Some of the new investigations have already revealed marvellous results, such as a 15 kW motor, low AC loss coils, low AC loss cables, etc.

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