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In-Situ High Temperature Optical Microscopic Observations of Crystallization Mechanism in NdBa2Cu3Ox

Published online by Cambridge University Press:  10 February 2011

D.K. Aswal ,
M. Shinmura ,
Y Hayakawa  and
M. Kumagawa
D.K. Aswal
Affiliation:
Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Japan Technical Physics and Prototype Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India
M. Shinmura
Affiliation:
Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Japan
Y Hayakawa
Affiliation:
Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Japan
M. Kumagawa
Affiliation:
Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Japan
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Abstract

The pseudo-binary NdBa2Cu3O-Ba3Cu10O13phase diagrams and the crystallization of NdBa2Cu3Ox have been in-situ observed using high-temperature optical microscopy in air and under three different reduced oxygen atmospheres namely, 1%, 0.1% and 0.0097% oxygen in argon. The liquidus line was found to become narrower both in composition and temperature with reducing oxygen content in the atmosphere. These results suggested that while in air NdBa2Cu3Ox can be crystallized from both high-temperature solution and peritectic melt; under reduced oxygen atmospheres the crystallization of NdBa2Cu3Ox is only possible from a peritectic melt. The in-situ observations of crystallization of NdBa2Cu3Ox from high-temperature solutions revealed that the growth mechanism changes from 3D via 2D layer-by-layer to continuos dendritic growth with increasing cooling rate. On the other hand, the NdBa2Cu3Ox crystallization from a peritectic melt involved two distinct steps (i) conversion of Nd4Ba2Cu2Ox into NdBa2Cu3Ox and (ii) nucleation and growth of NdBa2Cu3Ox The growth morphology in this case was independent of the cooling rate. This result and the direct observation of the dissolution of Nd4Ba2Cu2Ox into the liquid suggested that the solute diffusion is the rate-limiting factor.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 569: Symposium U – In Situ Process Diagnostics and Modelling , 1999 , 133
Copyright
Copyright © Materials Research Society 1999

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References

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