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Effect of a Nonplanar Melt-Solid Interface on Lateral Compositional Distribution during Unidirectional Solidification of a Binary Alloy with a Constant Growth Velocity VInfrared detector materials, such as Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te have energy gaps almost linearly proportional to its composition. Due to the wide separation of liquidus and solidus curves of their phase diagram, there are compositional segregations in both of axial and radial directions of these crystals grown in the Bridgman system unidirectionally with constant growth rate. It is important to understand the mechanisms which affect lateral segregation such that large uniform radial composition crystal is possible. Following Coriell, etc's treatment, we have developed a theory to study the effect of a curved melt-solid interface shape on the lateral composition distribution. The system is considered to be cylindrical system with azimuthal symmetric with a curved melt-solid interface shape which can be expressed as a linear combination of a series of Bessell's functions. The results show that melt-solid interface shape has a dominate effect on lateral composition distribution of these systems. For small values of b, the solute concentration at the melt-solid interface scales linearly with interface shape with a proportional constant of the product of b and (1 - k), where b = VR/D, with V as growth velocity, R as sample radius, D as diffusion constant and k as distribution constant. A detailed theory will be presented. A computer code has been developed and simulations have been performed and compared with experimental results. These will be published in another paper.
Document ID
19990102869
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Wang, Jai-Ching
(NASA Marshall Space Flight Center Huntsville, AL United States)
Watring, Dale A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Lehoczky, Sandor L.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Su, Ching-Hua
(NASA Marshall Space Flight Center Huntsville, AL United States)
Gillies, Don
(NASA Marshall Space Flight Center Huntsville, AL United States)
Szofran, Frank
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Metallic Materials
Meeting Information
Meeting: Optical Science
Location: Denver, CO
Country: United States
Start Date: July 19, 1999
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Other

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