Imperfections in Solids – I

Defects in Non-Stoichiometric Compounds: The compounds in which the ratio between numbers of anions to number of anions is not equal to ratio indicated by the formula.

  • Metal Excess Defect
  • Metal Deficiency Defect.

a. Metal Excess Defect: In these compounds there is an excess of cations along with the electrons occurs.

1. Anion Vacancy:

⇒ This free electron center is called F-centre.

⇒ Due to this only these compounds exhibits colour.

Anion Vacancy

2. Interstitial cation:

⇒ In this one of the cation will present at the interstitial position and which is stabilized by the electron at interstitial position.

⇒ In this the number of cations are not equal to the number of anions.

Interstitial cation

b. Metal Deficiency Effect:

1. Cation Vacancy: One cationic space is empty instead of that a positive cation will present in order to maintain the electrical neutrality.

Cation Vacancy

2. Interstitial Anion: In this defect the anion occupies interstitial position and one of the cation will be in its +2 oxidation state.

Interstitial Anion