Development of (Re)BaCuO Coated Conductors by Liquid Phase Epitaxy
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Abstract
Since the discovery of high-temperature superconductors, there has been a worldwide effort
towards the development of processes for fabricating coated conductors for power
applications. Most of these processes are based on vapour phase deposition techniques that
have relatively low growth rates. A high-rate processing route was proposed based on the
observation of high growth rate of (RE)Ba2Cu3O7- δ superconducting compounds (RE = rareearth
element) from a flux supersaturated with one or more RE elements by liquid phase
epitaxy (LPE).
LPE has been successfully used to grow YBCO thick films with both c- and a,b-orientations
on (110) NdGaO3 substrates and pure c-oriented films on YBCO seeded (100) MgO and (100)
SrTiO3 under carefully controlled growth temperature and undercooling. The film growth
mode (c- or a,b-oriented) is determined by the growth rate, which is directly related to the
level of RE supersaturation that could be controlled by the undercooling used along with the
amount of total RE solubility in the solution. The LPE grown films were highly epitaxial and
biaxially aligned with good in-plane and out-of-plane textures. YBCO thick films grown on
NdGaO3 by LPE showed high Tc of ~92 K and zero-field Jc at 77 K of 2.5×105 A/cm2.
The initial growth of YBCO was found to be a multi-nucleation process. However, above a
critical film thickness, dislocations started to form as a lattice-misfit stress relieving
mechanism that led to step formation and spiral growth around dislocation cores. The growth
kinetics from an unstirred solution was found to obey a