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Theory and technology of growing striation-free crystals

  • Journal of the Korean Crystal Growth and Crystal Technology
  • Abbr : J. Korean Cryst. Growth Cryst. Technol.
  • 2004, 14(4), pp.174-186
  • Publisher : The Korea Association Of Crystal Growth, Inc.
  • Research Area : Engineering > Materials Science and Engineering

Hans J. Scheel 1

1SCHEEL CONSULTING

Accredited

ABSTRACT

Striations are growth-induced inhomogeneities which hamper the applications of solid-solution crystals and of doped crystals in numerous technologies. Thus the optimized performance of solid solutions often can not be exploited. The inhomogeneity problem can be solved in specific cases by achieving a distribution coefficient one in growth from melts and from solutions. Macrostep-induced striations can be suppressed by controlling the growth mode, by achieving growth on facets thereby preventing step bunching. Thermal striations are commonly assumed to be caused by convective instabilities so that reduced convection by microgravity or by damping magnetic fields was and is widely attempted to reduce such inhomogeneities. Here it will be shown that temperature fluctuations at the growth interface cause striations, and that hydrodynamic fluctuations in a quasi-isothermal growth system do not cause striations. The theoretically derived conditions were experimentally established and allowed the growth of striation-free crystals of KTa1 - xNbxO3 밙TN  solid solutions. Hydrodynamic variations from the accelerated crucible rotation technique ACRT did not cause striations as long as the temperature was controlled within 0.03o at 1200oC growth temperature. Alternative approaches to solve or reduce the segregation and striation problems in growth from melts and from solutions are discussed as well.

Citation status

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