Module 2: Defect Chemistry and Defect Equilibria
  Defect Structures in Non-Stoichiometric Oxides
 

 

       2.5.2 Metal Deficient Oxides

  • Formation of either metal vacancies or oxygen interstitials (excess oxygen)

  • Formation occurs typically at the surface.

       The following cases are possible:

       2.5.2.1 If metal deficiency is dominating defect then

  • Depicted as metal deficient oxide M1-yO (y is the extent of non-stoichiometry)

  • Possible defect reaction is that of electronic compensation.

  • Creation of holes

  • Conduction due to holes i.e. a p- type conductor

  • Examples of oxides showing this characteristics are MnO, NiO, CoO, FeO etc.

      2.5.2.2 If metal deficiency is dominating defect then

  • Oxides depicted as MO2+x

  • Oxygen interstitials can form due to following reaction

  • P-type conductor

  • Example can be an oxide like UO2.