Influence of Crystallographic Orientation on the Charge Formation during Phase Changes in Solids

The effect of charge separation during phase changes (Costa Ribeiro effect) is studied with naphthalene single crystals. By properly seeding the melt the authors showed that the effect is dependent on crystallographic orientation. Values of the trapped charge are 32×10−9 C/g for growth normal to cleavage plane, 2.5×10−9 C/g for growth along b axis, and 2.9×10−9 C/g for growth along a axis. If the effect is due to selective ionic trapping in the solid phase this observation may be important in zone refining techniques. If it is due to an electronic effect this points out to an orientation dependent double-layer at the solid-liquid interface.