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Defects in Crystal structures and the types
The document discusses crystal imperfections, categorizing them into point defects, line defects (dislocations), and surface defects. Point defects include vacancies, interstitial atoms, and substitutional defects, which affect the structural integrity of crystals, while dislocations are irregularities in atomic arrangement. Surface defects involve boundaries that separate regions within a material, such as grain boundaries and stacking faults.
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Defects in Crystal structures and the types
- 1. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections • Point defects • Line defects or Dislocations • Surface defects Pure iron is relatively soft, yet we add small amount carbon and make it strong carbon steel
- 2. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Point defects • A point defect is a structural irregularity in a crystal lattice where an atom or ion is missing or in the wrong place • Dopants are elements thar are deliberately added in known concentrations at specific locations • Dopants – Phosphorus (P) and Boron (B) added to silicon crystals
- 3. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Point defects a) Vacancy b) Interstitial atom (unoccupied position) c) Small substitutional (replaced) d) Large substitutional e) Frenkel defect f) Schottky defect
- 4. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Dislocations or line defects • Line defects, also known as dislocations, are irregularities in the arrangement of atoms in a solid 1. screw dislocation 2. edge dislocation 3. mixed dislocation
- 5. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Screw dislocation
- 6. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Edge dislocation
- 7. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Mixed dislocation
- 8. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections
- 9. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Surface defects • the boundaries are planes thar separate a material into regions, each region having the same crystal structure but different orientations 1. grain boundaries 2. stacking fault 3. twin boundaries
- 10. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Grain boundaries
- 11. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Stacking fault
- 12. Dr VINOTH HARI UNIT1 S2 Crystal Imperfections Twin boundaries