On the Electronic Conduction in Dry Thin Films of Prussian Blue, Prussian Yellow, and Everitt's Salt

Electron conductivities are reported for dry thin films of Prussian blue and its completely oxidized and reduced forms, Prussian yellow and Everitt's salt. It has been discovered that desiccated Prussian blue films are non‐ohmic in the sense that significant electron conduction does not occur below a threshold voltage of . Prussian yellow and Everitt's salt are ohmic and do not have a conduction threshold. The conductivities, as determined from the slopes of the i‐V curves, are essentially the same for Prussian yellow, Everitt's salt, and Prussian blue above the voltage threshold, and are . The solid state voltammogram of a wet film is also considered in terms of the persistence of the threshold and the onset of electrochemistry. We propose a qualitative explanation for the threshold voltage based on the assumption that the "valence band" (ferric ferrocyanide) is completely occupied and that the applied voltage injects electrons into the "conduction band" (ferrous ferricyanide).