In situ observation and analysis of faceted crystal growth process in REBCO superconductive oxide

To clarify the nucleation and growth process of 123 crystals, growth of faceted RE123 (REBa2Cu3O7−X, RE = Nd, Sm, Gd, Y) crystals was observed in situ on MgO(1 0 0) by using high temperature optical microscope with zoom lens. RE123 crystals nucleated and grew at each undercooling (ΔT = 13-50 K). Growth rate (u) and incubation time (tinc) for nucleation were obtained from the relationship between the position of faceted interface and time (t). u increased with increasing ΔTr2, where ΔTr = ΔT/Tp, Tp was peritectic temperature. Nucleation rate (Iv) was obtained from the relationship between the number of nucleated crystals (n) and time. Iv increased with increasing of exp(-B/ΔTr2), where B was a constant. Both u and Iv under a fixed ΔT increased with increasing Tp: u(Nd123) > u(Sm123) > u(Gd123) and Iv(Nd123) > Iv(Sm123) > Iv(Gd123) for Tp(Nd123) > Tp(Sm123) > Tp(Gd123) in Ar-1%O2 atmosphere.