Yuichi Ikuhara

Preparation of YBa2Cu3O7-y thick film on YSZ substrate by Liquid Phase Epitaxy

We prepared YBa2Cu3O7-y (YBCO) thick film of about 10|Lim on yttria stabilized zirconia (YSZ) substrate by the liquid phase epitaxy (LPE) method. We successfully obtained the highly c — axis oriented YBCO film due to control of the initial temperature difference between the substrate and the surface of the melt (Δt) larger than 50°C. The behavior of hysteresis of the magnetization of film (ΔM) agrees well with the microstructure of this film. The T c and the J c estimated from ΔM of the film were 89.5K and 1.0 x 105 A/cm2 at 77K, 1T, respectively. These values enable us to apply the LPE grown thick film for applications at 77K.

Grain Boundaries and Critical Current Density of YBa2Cu3O7-y Thick Film Prepared by Liquid Phase Epitaxy

Superconducting YBa2Cu3O7-y thick films were fabricated by liquid phase epitaxiay (LPE) on the MgO (100) single crystalline substrate. The transport supercondcting characteristics of the films depends on the crystalline in-plane alignment of the film. The basal plane grain boundaries with large tilted angle of 36 ° and 45 ° were found by transmission electron microscope observation in the film of the low critical current density. The large tilt angle grain boundaries behave as a resistive type grain boundary and lower transport J c of the YBCO film. Theses boundaries were formed by the coalescence of island grown YBCO layer due to the multi-nucleation and growth mode of the hetero-epitaxial growth on the MgO (100) substrate.

Orientation mechanism of liquid phase epitaxial grown YBa2Cu3O7-y film

Superconducting YBa2Cu3Oy films were grown by liquid-phase epitaxy (LPE) on NdGaO3(l10) single-crystalline substrate by a modified top-seeded crystal growth method. Two different melt compositions were used. In the case of Cu-poor melt composition (Ba:Cu=3.0:5.0), only c-axis oriented growth was observed. However, if we used Cu-rich melt composition (Ba:Cu=3.0:6.5), both c-axis and a-axis oriented films were obtained. In the latter case the crystalline orientation of YBa2Cu3Oy films was dependent on the temperature of the surface of the melt. At lower temperatures, c-axis orientation films were obtained, whereas the films showed a-axis orientation at higher temperatures. The width of transition temperature range of orientation is very narrow, less than 3 °C, compared to the width observed in the conventional vapor phase depositions (which is typically 50 °C). We propose that orientation change in the liquid phase epitaxial growth is determined by the unique properties of the phase diagram of Y-Ba-Cu-O-system.