Metal oxide bulk doping lattice

Enhancement of reactivity of incendiary components has been claimed by the introduction of impurity states, particularly into metallic oxides (Refs 56 86). Impurity states have a twofold effect they disturb the lattice structure of the oxide (and[ so increase the diffusivity of the reactants), and they disturb the electronic distribution on the surface as well as in the bulk. The argument is made that by doping the oxide, or by controlling the formation temp, one may change an oxide from an n-type to a p-type semiconductor and hence cause it to become a better electron acceptor, and vice versa... 

The metal oxide sensors are typically based on tin oxides with varying amounts of the catalytic doping metal (Pd or Pt) (29). However, sensors can also be made with other metals (30). Metal oxides are semiconducting materials which are gas sensitive. Oxygen in the air reacts with lattice oxygen vacancies in the bulk material removing electrons from the material. 

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