Wurtzite boron nitride

Boron nitride, wurtzite BN a P6imc hex Wurtzite Metastable under aU conditions Fig. 4.1-3... 

Riter J R Jr 1973 Shock-induced graphite.far.wurtzite phase transformation in boron nitride and implications for stacking graphitic boron nitride J. Chem. Phys. 59 1538... 

The cubic zinc blende form of boron nitride is usually prepared from the hexagonal or rhombohedral form at high (4—6 GPa (40—60 kbar)) pressures and temperatures (1400—1700°C). The reaction is accelerated by lithium or alkaline-earth nitrides or amides, which are the best catalysts, and form intermediate liquid compounds with BN, which are molten under synthesis conditions (11,16). Many other substances can aid the transformation. At higher pressures (6—13 GPa) the cubic or wurtzitic forms are obtained without catalysts (17). 

Boron nitride can also form a superhard hexagonal phase in wurtzite-type (w-BN). This modification is a high pressure phase and was described first by Bundy and Wentorf [19]. 

There are three polytypes of boron nitride (BN), namely those with cubic(c-BN), wurtzite-type(w-BN) and hexagonal(h-BN) structures. Because the ELNES spectrum reflects the difference of the local structure, ELNES for h-BN, which has a graphite-type layered structure, shows considerably different spectrum from the other polytypes " " as shown in Fig.20. Among these polytypes, the near edge structures for c- and w-BN resemble each other, because of the similarity of their stmctures. As mentioned above. 

Boron compounds with nonmetals, i.e., boron hydrides, carbides, nitrides, oxides, silicides, and arsenides, show simple atomic structures. For example, boron nitride (BN) can be found in layered hexagonal, rhombohedral, and turbostratic or denser cubic and wurtzite-like structures, as well as in the form of nanotubes and fullerenes. Boron compounds with metalloids also differ from borides by electronic properties being semiconductors or wide-gap insulators. 

At some point you may have heard that diamond is the hardest material known to humankind. While diamond is extremely hard, there are actually a few materials that are even harder still Years ago, some synthetically produced nanomaterials were discovered that are even harder than diamonds. Even more recently, two additional naturally occurring materials, both of which are even harder yet, were discovered. These materials are wurtzite boron nitride and a mineral called lonsdaleite. Wurtzite boron nitride has its atoms arranged in a very similar structure to the arrangement in diamond, but they are just different atoms (boron and nitrogen, rather than carbon). The other material, lonsdaleite, is actually also made from carbon atoms, but these are arranged dif-... 

Versailles Agreement on Materials and Standards vapor phase formation and condensation process valence electron concentration vapor-liquid-solid process vapor-solid reaction wurtzitic boron nitride... 

Structurally, the cubic form of BN resembles diamond (Figure 6.19) and the two materials are almost equally hard. Crystalline cubic BN is called borazon and is used as an abrasive. A third polymorph of boron nitride with a wurtzite-type structure is formed by compression of the layered form at 12 kbar. 

Boron nitride exists in many different structures due to the special bonding behaviors of boron and nitrogen. Although the most well-defined crystallographic structures are hexagonal BN (h-BN), cubic BN (c-BN), and wurtzitic BN (w-BN), other crystalline structures, such as explosion boron nitride (e-BN) and ion beam-deposited boron nitride (i-BN) [124—135] and amorphous BN (a-BN) [136,137] also exist. 

Hexagonal Boron Nitride with Wurtzite Structure (y-BN) and Mixtures of Different BN Phases... 

Electronic Structure, Energy Bands, and Lattice Defects in Cubic (P-BN) and Wurtzite-Type (y-BN) Boron Nitride... 

Leonidov VYa, Timofeev IV, Lazarev VB, Bozhko AB (1988) Enthalpy of formation of the wurtzite form of boron nitride. Russ J Inorg Chem 33 906-908... 

Sokolowski M (1979) Deposition of wurtzite type boron-nitride layers by reactive pulse plasma crystallization. J Cryst Growth 46 136-138... 

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