Nobuyuki Mori1, Yoshiaki Nakahara2,, Seiji Fukamachi3,, Masashi Mukaida1 and Keisaku Ogi1,
1Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395
The growth process of RE123 (REBa2Cu3O7-x, RE=Nd and Sm) crystals in the atmosphere of Ar-1%O2 were observed in-situ to investigate the nucleation and growth process of faceted RE123 crystals from the liquid +422(Nd4Ba2Cu2O10) or 211(Sm2BaCuO5) on MgO(100) substrate through a peritectic reaction by using high temperature optical microscope with zoom lens. The nucleated faceted 123 crystals grew at a rate depended on the undercooling(Δ T). Growth rate(u) and incubation time (tinc) for nucleation were obtained from the changes in position of faceted interface during isothermal solidification. Growth rate u(m/s) was approximated by the following relation: u=Ag(Δ Tr2/η (T)), where η (T) was the viscosity, Δ T=Tp-T, Δ Tr=Δ T/Tp, T was temperature, Tp was peritectic temperature, Ag was a constant: Ag=0.60 × 106 for Nd and Ag =1.8 × 10-5 for Sm. Nucleation rate(Iv) was obtained from the relationship between the number of nucleated crystals(n) and time(t). Iv(m-3 s-1) was approximated by Iv=An(1/η (T)) exp (-B/Δ Tr2), where An and B were constants: An =3.5 × 107, B =1.5× 10-3 for Nd, and An=12.5 × 107, $B =3.2 × 10-3 for Sm.
NdBCO, SmBCO, NdBa2Cu3O7-x, SmBa2Cu3O7-x, Nd4Ba2Cu2O10, Sm2BaCuO5, nucleation, solidification, peritectic reaction
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