Defects and Impurities
Real crystals feature defects or irregularities in the ideal arrangements described above and it is these defects that critically determine many of the electrical and mechanical properties of real materials. When one atom substitutes for one of the principal atomic components within the crystal structure, alteration in the electrical and thermal properties of the material may ensue. Impurities may also manifest as spin impurities in certain materials. Research on magnetic impurities demonstrates that substantial alteration of certain properties such as specific heat may be affected by small concentrations of an impurity, as for example impurities in semiconducting ferromagnetic alloys may lead to different properties as first predicted in the late 1960s. Dislocations in the crystal lattice allow shear at lower stress than that needed for a perfect crystal structure.
Read more about this topic: Crystal Structure
Famous quotes containing the words defects and, defects and/or impurities:
“The defects and faults of the mind are like wounds in the body; after all imaginable care has been taken to heal them up, still there will be a scar left behind, and they are in continual danger of breaking the skin and bursting out again.”
—François, Duc De La Rochefoucauld (1613–1680)
“One of our defects as a nation is a tendency to use what have been called “weasel words.” When a weasel sucks eggs the meat is sucked out of the egg. If you use a “weasel word” after another there is nothing left of the other.”
—Theodore Roosevelt (1858–1919)
“In order for the wheel to turn, for life to be lived, impurities are needed, and the impurities of impurities in the soil, too, as is known, if it is to be fertile. Dissension, diversity, the grain of salt and mustard are needed: Fascism does not want them, forbids them, and that’s why you’re not a Fascist; it wants everybody to be the same, and you are not. But immaculate virtue does not exist either, or if it exists it is detestable.”
—Primo Levi (1919–1987)