The Controlled Sublimation Technique and Its Utilization for the Crystal Growth of Hexamine

A technique has been developed for the growth of large single crystals of hexamine from the vapor. The method is based on sublimation, with modifications that allow stringent control over the process. A single nucleation is induced at a localized cold spot, produced by a fine tipped temperature‐controlled copper rod, in contact with the wall of the growth ampoule. Another modification is the presence of four separate temperature zones. Single crystals of hexamine ∼ 2 cm 3 in volume were produced. The as‐grown crystals exhibited considerable strain because they were in contact with quartz during growth. A significant improvement in the mechanical and electrooptic properties was observed after annealing the crystals. The best electrooptic coefficient obtained was ; this corresponds to a half‐wave voltage of 15 kv (width/length). The technique described here should be applicable for the crystal growth of many other materials. It could be extended to low vapor pressure materials by utilizing chemical transport instead of sublimation.