Large-sized and highly-uniform superconducting RE123 single crystals by top-seeded solution-growth: A platform for physical research

The last two decades have seen a growing trend towards sizable single crystals of REBa₂Cu₃O_7−δ (RE123, RE = rare earth elements) with fine quality, which have been attracting considerable interest in the study of superconductivity. As an advanced and classic method, top-seeded solution-growth (TSSG) is the only technique to date for producing RE123 single crystals with dimensions of 2 cm, e.g., a Y123 single crystal of 19.8 × 19.5 mm² in a-b plane and 16.5 mm in height. Recently, novel approaches were developed such as crystal-pulling combined with continual cooling for rapid growth to attain a large-sized RE123 crystal, and the utilization of dopant-added crucibles for continuous growth to produce highly-uniform doped-Y123 crystals. Consequently, researchers from several tens of physical laboratories worldwide have been benefiting from TSSG-produced RE123 single crystals and generating excellent collaborative work. This paper provides an overview of the progress and achievements on the growth of superior RE123 single crystals by TSSG for fundamental studies and practical applications, focusing on three aspects including crystal enlargement, RE123 stoichiometry control and cation doping. The mechanism of crystal growth and the correlation between phase formation and superconducting properties are comprehensively elucidated on the basis of distinctive features of phase diagrams of RE–Ba–Cu–O systems.