IMPERFECTIONS IN SOLIDS

• Site from which an atom is missing.

  Surface analogue of a vacancy defect.
• Crystalline defect


  A lattice irregularity having one or more of its dimensions on the order of an atomic diameter.
• Point defects


  Atoms are missing or in irregular places in a crystal lattice.
• Vacancy


  Simplest type of a point defect.
• Another name of vacancy.

  Vacancy lattice site
• An absence of an atom from its normal location in a perfect crystal structure.

  Vacancy
• Bonding + Crystal structure + Defects = Properties
• All crystalline solids contain vacancies and it's impossible to create materials without vacancies.
• Temperature


  Dependence of the equilibrium number of vacancies.
• Self-interstitial


  An atom from the crystal that is crowded into an interstitial site.
• Interstitial site


  Small void space that under ordinary circumstance is not occupied.
• Interstitial site


  Exists in very small concentrations, lower than vacancies.
• Interstitial site


  In metals it introduces relatively large distortions in the surrounding lattice because the atom is substantially larger than the interstitial position in which it is situated.
• Impurities


  Another name of a foreign atom.
• Impurities.


  Atoms which are different from the host atoms.
• In pure metals, impurity or foreign atoms will always be present, some will exist as crystalline point defects; no only one type of atom.
• Alloy

  Deliberate mixture of atoms.
• Alloy


  Impurity atoms have been intentionally added to impart specific characteristics to the material.
• Another term for solid solution.

  Second phase
• Solid solution


  Result of addition of an impurity atom into a metal, depending on the kinds, concentration, and temperature of an alloy.\
• Solute


  Elements/compound in a minor concentration.
• Solvent


  Element/compound in the greatest amount.
• Another term for solvent.

  Host atom
• Solid solution


  Crystal structure must be maintained and no new structure is made. thus making it homogeneous after the mixing of a solute to a host material.
• Solid solution


  Contains dispersed impurities.
• Solubility


  Ability to dissolve.
• Liquid solution


  Formed when two liquids which are soluble with each other are combined and its composition is homogeneous throughout.
• Impurity point defects are found in solid solutions.
• Two types of solid solutions

  Substitutional and Interstitial
• Substitutional solid solution


  A solute or impurity atom will replace the host atoms.
• Interstitial solid solution


  An impurity atom will fill the voids or interstices among the host atoms.
• In atomic size factor, appreciable quantities of a solute may be accommodated in this type only when the difference in atomic radii between the two atom type is less than about +_15%. Otherwise the solute atoms will create substantial lattice distortions and a new phase will form.
• Crystal structure for metals of both atom types must be the same.
• The more electropositive one elements and the more electronegative the other, the greater is the likelihood that they will form an intermetallic compound rather than a substitutional solid solution.
• Electronegativities must be compatible.
• A metal will have more of a tendency to dissolve another metal with high valency than that of a lower valency.
• Metals with high APF will have interstitial position that is small.
• Atomic diameter of an interstitial impurity atom must be substantially smaller than that of the host atoms.
• Normally, the maximum concentration of interstitial impurity atom is less than 10%.
• Dislocations


  Linear/one dimensional defect around which some of the atoms are misaligned.