The applications of single crystals

Abstract

Abstract The word ‘crystal’ comes from a Greek word meaning clear ice which was also applied to rock crystal (clear, transparent quartz). It was not until about the 17th century that the word was extended to other naturally occurring, transparent minerals which showed a regularity of outward form. It was appreciated at this time that this regularity resulted from an inner symmetry of atomic arrangement and it has since been realized that almost all solid materials are, to some extent at least, crystalline although this is often not apparent from their outward appearance. Indeed most materials of practical importance are polycrystalline-they consist of an aggregate of randomly-arranged small crystals-although single crystals have been used for special purposes for some considerable time, e.g. the crystals of calcite that are used to make Nicol prisms, and the crystals of galena (lead sulphide) that were used in early ‘crystal’ wireless receivers. But in recent years increasing use has been made of single c...