Oriented and ordered structures by glass crystallization

Methods to prepare oriented and ordered structures by glass crystallization are described. Oriented glass ceramics can be obtained by three different routes: the thermodynamically controlled crystallization by attaching a mag netic or electric field, the kinetically controlled crystallization by nucl eating a melt solely in a small volume of the sample e. g. at the surface o r at an electrode inserted into the melt. The third method is the mechanica l deformation of the melt which might be partially crystalline. Numerous ex amples for materials produced by the two latter methods are given. Furtherm ore, further two methods to prepare ordered structures are described. First , hetero-epitaxial growth of a crystalline phase on an already oriented pha se enables the preparation of cross-wise oriented structures. Attaching a s tationary ultra-sonic wave to a partially crystalline melt results in perio dical arrangement of layers in which the crystalline phase occurs.