Carbon sitting in the octahedral void in FCC-iron is an example of……………a.Interstitial impurityb.Frankel defectc.Substitutional impurityd.Vacancy defect

Carbon sitting in the octahedral void in FCC-iron is an example of……………

The defect that occurs due to a displacement of an ion is known as……………a.Vacancy defectb.Frankel defectc.Schottky defectd.Impurity defect

In a solid lattice, the cation has left a lattice site and is located at an interstitial position, the lattice defect is :Interstitial defectValency defectFrenkel defectSchottky defect

We noted in Section 12.5 (Figure 12.20) that in FeO (wüstite), the iron ions can exist in both Fe2+ and Fe3+ states. The number of each of these ion types depends on temperature and the ambient oxygen pressure. Furthermore, we also noted that in order to retain electroneutrality, one Fe2+ vacancy will be created for every two Fe3+ ions that are formed; consequently, in order to reflect the existence of these vacancies the formula for wüstite is often represented as Fe(1 – x)O, where x is some small fraction less than unity. In this nonstoichiometric Fe(1 – x)O material, conduction is electronic, and, in fact, it behaves as a p-type semiconductor—that is, the Fe3+ ions act as electron acceptors, and it is relatively easy to excite an electron from the valence band into an Fe3+ acceptor state, with the formation of a hole. Determine the electrical conductivity of a specimen of wüstite that has a hole mobility of 1.0 × 10–5 m2/V.s and for which the value of x is 0.040. Assume that the acceptor states are saturated (i.e., one hole exists for every Fe3+ ion). Wüstite has the sodium chloride crystal structure with a unit cell edge length of 0.437 nm.

Number of tetrahedral voids in the FCC unit cell is