Solid-State Chemistry with Nonmetal Nitrides

Among the nonmetal nitrides, the polymeric binary compounds B N and S i 3 N 4 are o f partic­ ular interest for the development of materials for high-performance applications. The out­ standing features o f both substances are their thermal, mechanical, and chemical stability, coupled with their low density. Because of their extremely low reactivity, boron and silicon nitride are hardly ever used as starting materials for the preparation o f ternary nitrides, but are used primarily in the manufacture of crucibles or other vessels or as insulation materials. The chemistry of ternary and higher nonmetal nitrides that contain electropositive elements and are thus analogous with the oxo compounds such as borates, silicates, phosphates, or sulfates was neglected for many years. Starting from the recent successful preparation of pure P 3 N 5 , a further binary nonmetal nitride which shows similarities with S i 3 N 4 with regard to both its structure and properties, this review deals systematically with the solid-state chemistry o f ternary and higher phosphorus(v) nitrides and the relationship between the various types of structure found in this class of substance and the resulting properties and possible applications. From the point o f view o f preparative solid-state chemistry the syntheses, structures, and properties of the binary nonmetal nitrides B N , S i 3 N 4 , and P 3 N 5 wi l l be compared and con­ trasted. The chemistry o f the phosphorus(v) nitrides leads us to expect that other nonmetals such as boron, silicon, sulfur, and carbon wil l also participate in a rich nitride chemistry, as initial reports indeed indicate.