SINGLE CRYSTALS

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SINGLE CRYSTALS

• ISSUES TO ADDRESS
• -What is single crystal ?
• -Most widely used Crystal Growth methods
• -Single crystal materials and their industrial
  applications

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WHAT IS SINGLE CRYSTAL ?

• Single crystal is a crystalline solid material
  in which periodic and repeated arrangements of
  atom is perfect and extends throughout the entire
  sample with no interruption and grain boundaries
  .
• -----IMPORTANT FACTS-------
• Since grain boundaries have significant effect
  on material properties especially on mechanical,
  optical and electrical ones, grain boundaries are
  the main concern of studies in single crystals.
• Because of the thermodynamic effects of
  surrounding on the microstructure of materials,
  stress effects of impurities and mobility of
  crystallogrophich defects and dislocations,
  natural formation of single crystals in
  significance size are exceedingly rare in nature.
• Moreover single crystal growth is also diffucult
  in the under controlled laboratory conditions,
  because most of them are relied on emprical
  enginering and trial-error techniques due to
  influence of numerous interdependent parameter.
• Most of growth techniques are based on the
  fact
• GRAINS ALIGN THEMSELVES WITH HEAT FLOW
  DIRECTION.

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SINGLE CRYSTAL GROWTH METHODS
Czochralski Method
Flaot Zoning

Bridgman Stockbarger
Vapor Phase Epitaxy
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Most Widely Used Single Crystal Materials
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INDUSTRIAL APPLICATIONS

• SILICON
• - Predictable , reliable electronic properties
• - Extensive usage in fabrication of
  semiconductor
• -Fundamental material of electronic circuits and
  devices.
• -microprocessors

• SAPPHIRE
• Advanced light transmission property and good
  heat conductivity and resistivity.
• - First ever laser produced is based on the
  sapphire (ruby chromium impurity in saphire).
• - Vacuum equipments, windows in reaction
  furnaces, scanner windows and caps for optical
  communication .

• S.C. SUPPERALLOYS
• -Advanced mechanical strength and enhanced creep
  resistance at high temperatures, good corrosion
  and oxidation resistance.
• -With single crystal super alloys operation
  temperature has advanced up to 1373 K from 973 K
  .
• - Turbine blades, jet engines, minature gas
  turbines (micro turbines).