Cubic silicon carbon nitrides

Superhard compounds are obviously formed by a combination of the low atomic number elements boron, carbon, silicon, and nitrogen. Carbon-carbon as diamond, boron-nitrogen as cubic boron nitride, boron-carbon as boron carbide, and silicon-carbon as silicon carbide, belong to the hardest materials hitherto known. Because of their extreme properties and the variety of present and potential commercial applications, silicon carbide (SiC) and boron carbide (B4C) are, besides tungsten carbide-based hard metals, considered by many as the most important carbide materials. 

The layer sequence of the 111 plane is ABCABCABC which means that every third layer is identical (Fig. 7.3).1 1 This gives a Ramsdell notation of 3C SiC where the numeral 3 refers to the number of layers of carbon atoms and silicon atoms necessary to produce a unit cell and C indicates cubic symmetry. It is analogous to the diamond structure and is also the structure of cubic boron nitride (see Ch. 12). 

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