Effect of Bromine on the Dark Conductivity of Silver Bromide

The dark conductivity of silver bromide in a bromine atmosphere increases with increasing bromine pressure. The conductivity increases are proportional to the square root of the halogen pressure in the range between 10 and 200 mm of mercury, at temperatures between 25°C and 200°C. The increases agree with those calculated from the corrosion data of Wagner and Teltow, and they are probably caused by positive holes. The increases are affected by the purity of the crystals, and the rate of equilibrium attainment depends on the structure and purity of the samples. In particular, the presence of small amounts of silver in the crystals prevents attainment of equilibrium until all the silver is removed. The rate of silver removal depends on the positive-hole conductivity. The results are in good agreement with the corrosion mechanism suggested by Wagner.