Toshihiro Suga

YBa2Cu3O7−δ deposition on Ni–Cr alloy tape by liquid phase epitaxy method

Abstract Thick YBa 2 Cu 3 O 7− δ (YBCO) films have been successfully formed by the liquid phase epitaxy (LPE) method on Ni–Cr alloy tape. A buffer layer of yttria stabilized zirconia and seed layer of YBCO were formed by the ion beam assisted deposition and by the pulsed laser deposition method, respectively. YBCO films have been grown from the solution of BaO–CuO–Ag–BaF 2 at 820, 845 and 860 °C under low oxygen partial pressure of 2% to prevent the metallic substrate from reacting with the solution. Good YBCO films are obtained by the growth at 820 °C, and the best one shows high critical current density of 1.9 MA/cm 2 . A cross-sectional observation by high resolution scanning electron microscopy shows neither reaction layer nor damaged region at the substrate/YBCO film interface. θ –2 θ and pole figure X-ray diffraction of the seed layer and the YBCO LPE layer show that in-plane orientation distribution is highly improved by the LPE process.

Fabrication of seed/buffer layers on metallic substrates for YBCO coated conductors

Abstract LaNiO 3 (LNO) buffer layers with good c -axis orientation on SrTiO 3 (STO), LaAlO 3 (LAO), NiO/STO and SOE (NiO/Ni) tapes were successfully fabricated by the pulsed laser deposition (PLD) method. Biaxially aligned neodymium (NdGaO 3 , NGO) seed layers were successfully fabricated on the STO, LAO and LNO buffer layer by PLD method and post-annealing process. And also, the good biaxial orientation YBa 2 Cu 3 O 7− δ (YBCO) films on NGO seed layers were deposited by liquid phase epitaxy (LPE) method. From this work, it has been proved for the first time that NGO thin film can be used as a seed layer for YBCO thick film deposition by the LPE method. This NGO thin film which is deposited by the PLD method at room temperature and post-annealed at 950°C for 5 h in air, is low cost and very effective for the coated conductor production by LPE.

Non-cuprate thin films as candidates of seed layer for liquid phase epitaxy process

Abstract As a seed layer for the liquid phase epitaxy (LPE) of YBa2Cu3O7−d (YBCO) we investigate non-cuprate thin film of Y–Ba–Fe–O deposited by pulsed laser deposition (PLD) method. The deposited film is highly oriented and it can be used as a seed layer at LPE temperatures below 980°C. PLD conditions for obtaining crystalline Y–Ba–Fe–O film is much wider than that for the seed layer of YBCO. LPE-grown YBCO film formed on the Y–Ba–Fe–O seed layer shows the same superconductive properties as that formed on the YBCO seed layer.

Low temperature formation of YBCO coated conductors on textured metal tapes by liquid phase epitaxy

Abstract We have formed YBCO films on Ag–Cu (2 1 0)〈1 2 0〉 and Ni (1 0 0)〈0 0 1〉 textured metal tapes. By using a furnace equipped with a reel-to-reel tape moving mechanism, continuous coating of YBCO film has been made on the silver-based tape at 925 °C. There were, however, cracks in the film prepared at 925 °C due to penetration of the solvent between the metal substrate and the YBCO film. By reducing the growth temperature to 880 °C, thick films over 5 μm in thickness have grown on the tape with neither intrusion nor reaction at the interface. YBCO film on nickel tape showed that the transition temperature degraded considerably at higher growth temperatures, which is probably due to reaction of Ni with the solution and contamination of Ni in the film.