日本金属学会誌

J. Japan Inst. Metals, Vol. 70, No. 7 (2006),
pp. 592-598

In-Situ Observation and Analysis of Crystal Growth Process in NdBCO and SmBCO Superconductive Oxide

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
2Department of Materials Physics and Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395
3Department of Materials Process Engineering, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395

Abstract:

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.


(Received 2006/4/28)

Keywords:

NdBCO, SmBCO, NdBa2Cu3O7-x, SmBa2Cu3O7-x, Nd4Ba2Cu2O10, Sm2BaCuO5, nucleation, solidification, peritectic reaction


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