impurity defect

Impurity defects are foreign atoms that replace some of the atoms making up the solid or that squeeze into the interstices; they are important in the electrical behaviour of semiconductors, which are materials used in computer chips and other electronic devices.

In another defect, called an impurity, an atom is present that is different from the host crystal atoms. Impurities may either occupy interstitial spaces or substitute for a host atom in its lattice site.

…when they are found as impurities in nonmagnetic crystals. They usually retain their magnetic moment, so small magnets are distributed randomly throughout the crystal. If the host crystal is a metal, the magnetic impurities make an interesting contribution to the electrical resistivity. The conduction electrons scatter from the magnetic impurity.…