Influence of electronic and ionic processes on electrical properties of TlBr crystals

We demonstrate experimentally that Tl+ ions are responsible for the ionic conduction mechanism at temperatures higher than 250 K. The main change of the current versus time dependence (500 h) corresponds to the same amount of electric charge that the evaporated Tl layer could carry as Tl+ ions. A new, unexpected result was found in direct Tl+ ion transport: diffusion-limited aggregation is responsible for dendrite structures, which could grow by the electrodiffusion of Tl+ ions. The analysis of fractal formation by the electrodiffusion of Tl+ ions seems very promising to understanding the polarisation phenomena in TlBr.