Imperfection in Solids Flashcards
all contain large numbers of various defects
imperfections.
refers to a lattice
irregularity having one or more of
its dimensions on the order of an
atomic diameter.
Crystalline Defect
the simplest of the point one
normally occupied but from which an atom is missing defects
Vacancy or vacant lattice site
is an atom from the crystal that is crowded into an interstitial
site—a small void space that
under ordinary circumstances is
not occupied.
self-interstitial
3 IMPERFECTION IN SOLIDS
Point Defects
Impurities in solids
Linear Defects (dislocation)
impurity or foreign atoms are always present, and some exist as
crystalline point defects.
IMPURITIES IN SOLIDS
Impurity point defects are found in solid solutions, of which there are two types:
1.) Substitutional solid solution
2.) Interstitial solid solution
Several features of the solute and solvent atoms determine the
degree to which the former dissolves in the latter. (four Hume–Rothery rules)
- Atomic size factor.
- Crystal structure.
- Electronegativity factor.
- Valences.
Appreciable quantities of a solute may be accommodated in this type of solid solution only when
the difference in atomic radii between the two atom types is
less than about 15%.
Atomic size factor
For appreciable solid solubility, the crystal structures for metals of both atom types must be the same.
Crystal structure.
The more electropositive one element and the more electronegative the other, the greater the likelihood that they will
form an intermetallic compound instead of a substitutional solid solution.
Electronegativity factor.
Other factors being equal, a metal has more of a tendency to dissolve another metal of higher valency than to dissolve one of a lower valency.
Valences.
impurity atoms fill the voids
or interstices among the
host atoms
Interstitial solid solution
the weight of a particular element
relative to the total alloy weight.
Weight percent (wt%)
