Materials Science Glossary - E

edge dislocation. A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers  vector is perpendicular to the dislocation line.

elastic deformation. Deformation that is nonpermanent—that is, totally recovered upon release of an applied stress.

elastic recovery. Nonpermanent deformation that is recovered or regained upon release of a mechanical stress.

elastomer. A polymeric material that may experience large and reversible elastic deformations.

electrical conductivity. See conductivity, electrical.

electric dipole. See dipole (electric).

electric field (e). The gradient of voltage.

electroluminescence. The emission of visible light by a p–n junction across which a forward-biased voltage is applied.

electrolyte. A solution through which an electric current may be carried by the motion of ions.

electromotive force (emf) series. A ranking of metallic elements according to their standard electrochemical cell potentials.

electron configuration. For an atom, the manner in which possible electron states are filled with electrons.

electronegative. For an atom, having a tendency to accept valence electrons. Also, a term used to describe nonmetallic elements.

electron energy band. A series of electron energy states that are very closely spaced with respect to energy.

electroneutrality. The state of having exactly the same numbers of positive and negative electrical charges (ionic

and electronic)—that is,of being electrically neutral.

electron state (level). One of a set of discrete, quantized energies that are allowed for electrons. In the atomic case each state is specified by four quantum numbers.

electron volt (eV). A convenient unit of energy for atomic and subatomic systems. It is equivalent to the energy acquired by an electron when it falls through an electric potential of one volt.

electropositive. For an atom, having a tendency to release valence electrons. Also, a term used to describe metallic elements.

endurance limit. See fatigue limit.

energy band gap. See band gap energy.

engineering strain. See strain, engineering.

engineering stress. See stress, engineering.

equilibrium (phase). The state of a system in which the phase characteristics remain constant over indefinite time periods. At equilibrium the free energy is a minimum.

erosion–corrosion. A form of corrosion that arises from the combined action of chemical attack and mechanical wear.

eutectic phase. One of the two phases found in the eutectic structure.

eutectic reaction. A reaction wherein, upon cooling, a liquid phase transforms isothermally and reversibly into two intimately mixed solid phases.

eutectic structure. A two-phase microstructure resulting from the solidification of a liquid having the eutectic composition; the phases exist as lamellae that alternate with one another.

eutectoid reaction. A reaction wherein, upon cooling, one solid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed.

excited state. An electron energy state, not normally occupied, to which an electron may be promoted (from a lower energy state) by the absorption of some type of energy (e.g., heat, radiative).

extrinsic semiconductor. A semiconducting material for which the electrical behavior is determined by impurities.

extrusion. A forming technique whereby a material is forced,by compression, through a die orifice.