Growth of Silver Filaments and Dendrites*

Filaments and dendrites of silver have been formed by transfer of silver through a layer of silver halide which has been put in contact with a silver block at about 400°C. According to the scheme proposed for explanation of the observations, silver dissolves in the silver halide and migrates as interstitial ions, transfer occurring because of the existence of a concentration gradient. At the same time vacant anion sites are formed in the reaction at the interface of the block and the silver halide which permit the migration of halide ions toward the silver block. When the rate of silver migration is relatively slow, as with silver bromide or silver chloride, dendrites usually form by migration of silver on the silver already formed. When the silver transfer is fast, as with silver iodide, the migration process does not remove the silver quickly enough and the silver is extruded as long filaments.