The Influence of Gas Pressure upon Conductivity

Most important from the viewpoint of lattice disorder are the observations of Wagner and his co-workers upon changes of conductivity brought about by surrounding the crystal by a gas atmosphere of its electronegative component (oxygen for oxides, or halogen for halides). These measurements were the basis of the classification of lattices, as in the previous section, into those with anion excess, cation excess, or stoichiometric cation anion ratio. 

The conductivity, which in cuprous oxide is mainly electronic, is thus proportional to the eighth root of the pressure of oxygen. While the theory predicts an eighth root, experiment 

Column 2. There are almost equal numbers of interstitial cations and vacant cation sites in the silver chloride lattice. The number of quasi free electrons or electron-defect sites is nejgligible. 

Column 4. Neither silver nor chlorine is in any appreciable excess over their stoichiometric ratio. 

Columns 5, 6 and 7. Increased partial pressure of chlorine has no influence upon conduction due to cations, but may alter the electronic conductivity. Electronic conductivity (columns 2 and 9) occurs however only to a negligible extent. 

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