i m not able 2 understand the metal excess & metal deficieny dfect

Asked by KSHITIJ BHARDWAJ | 28th Aug, 2010, 04:26: PM

Expert Answer:

Together these   called non-stoichiometric defects.

Metal excess may occur in either of the following two ways

By presence of extra cations in the interstitial sites:Extra cations may occupy interstitial sites with electrons present in another interstitial site to maintain electrical neutrality.
 
By anionic vacancy: A negative ion may be missing from its lattice site, leaving a hole, which is occupied by an electron thereby maintaining an electrical balance.The trapped electrons are called F-centers or color centers because they are responsible for imparting color to the crystal.
 
Metal deficiency defects generally occur when metals show variable valency. It occurs due to the missing of a cation from its lattice site and presence of the cation with higher charge
Crystals having metal deficiency are generally semiconductors

Answered by  | 28th Aug, 2010, 06:40: PM

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