A Model for Structures Growth by Sodium Electrodiffusion in Quartz Crystals

Dendritic structures were grown inside the quartz crystal by electrodiffusion of sodium ions from a NaCl layer at the anode. The electric field was applied along the optical axis Z and the structures were grown in the xy plane. An experimental arrangement using a pointed cathode and a graphite plate anode was employed. X ray diffraction analysis shows that the structures' chemical composition is a mixture of sodium silicates. To explain the structures' growth a model is proposed. The model is a bidimensional one. The transport of the particles along the Z axis structural channels by the electric field was taken into account by introducing a probability of generating the particles in the growth plane as a function of the distance to the cathode. The computer generated results and the experimental ones were compared and a good correlation was found.