Electrodecoration of tilt grain boundaries in potassium bromide bicrystals

Electric fields applied at 200°-250°C to KBr bicrystals with silver electrodes produce a pattern of silver colloids within the boundary that directly reveals macroscopic growth structure and indirectly gives information about boundary dislocations. The colloids appear to form at sites of second-phase precipitate that nucleates at boundary dislocations and imperfections even in pure crystal. Electrodecoration is aligned along tilt-axis dislocations in 5° and 10° boundaries, but not in 20° boundaries, suggesting that the dislocation model is not appropriate at the larger angle. Observations on serrated boundaries, obtained when tilt is asymmetrical, show that dislocations in 10° (001) boundaries with a [100] tilt axis are crystal lattice dislocations of {011} 〈011〉 type.