A Method of Growing Oriented Sections of Certain Optical Crystals

A new method is described for growing extended crystal sections normal to a threefold axis from melts of sodium nitrate, and of certain alkali halides such as potassium bromide and potassium iodide. Such sections result when crystallization in the melt is started at a mica cleavage surface and is allowed to proceed in a direction normal thereto, the mica acting as an insoluble, infusible seed for the new crystal growth. The mica cleavage surface adsorbs from the melt a hexagonal net of alkali ions whose side is 5.17A, and this plane net constitutes the first layer of the new crystal growth.