Low-Pressure Synthesis of c-BN

Low-pressure deposition of diamond is a commonly used industrial process [184]. Because HP-HT synthesis for c-BN and diamond works under similar conditions, it was assumed that the low-pressure synthesis of c-BN should be possible analogous to that of diamond. However, there are a lot of differences between c-BN and diamond that make a low-pressure deposition of c-BN rather difficult  

Deposition of nano-cBN films is possible with ion-assisted CVD and ion-assisted PVD techniques. Since the c-BN crystal size in such layers is in the range of nanometers, such layers should be called nano-cBN. The amount of grain boundaries in such materials is rather high and this fact should not be negated by using the notation pure c-BN . 

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Actually, a spontaneous nucleation of c-BN from a degradation of Li3BN2 will not occur due to the fact that the less dense phase will nucleate first according to the Ostwald-Volmer rule, which is a general rule of thumb for the kinetic behavior of reactions [237]. Thus, seeding with c-BN can overcome this problem. Hence, this approach seems to be well suited to develop a low-pressure synthesis of c-BN. 

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