Which of the following is NOT a point defect?

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APPSC Lecturer (Polytechnic Colleges) Held on March 2020
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  1. Edge dislocation
  2. Vacancy
  3. Substitutional impurity
  4. Interstitial impurity

Answer (Detailed Solution Below)

Option 1 : Edge dislocation

Detailed Solution

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Explanation

Imperfection/Defect:

  • An ideally perfect crystal in one which has same unit cells and contains some lattice point throughout the crystals 
  • Imperfections or defect is generally used to describe any deviation of the ideally perfect crystal from the periodic arrangement of its constituents. Defects can exist in any solid material.

Crystalline defects:

  • Crystalline defects mean a lattice irregularity having one or more of its dimensions on the order of an atomic diameter
  • Defects in the crystalline structure can have a tremendous effect on material behaviour.
  • Physical, electrical, magnetic and the optical properties of crystalline materials can be modified by controlling the imperfections in their lattice structure
  • For ease of their characterizations defects are classified on the basis of their geometry. 

Classification of structural imperfection

Point Defect(0D)

Line Defect(1D)

Surface Defect (2D)

Volume Defect(3D)

Vacancies

Self Interstitialcy

Impurities

  • Interstitial
  • Substitutional

Frenkel Defect

Schottky Defect

 

Edge Dislocation

Screw Dislocation

Grain boundaries

Low angle boundaries

  • Tilt boundaries
  • Twist boundaries

Twin boundaries

Stacking Fault

Casting defects

Welding Defects

Forming Defects

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