Characterization of BN Products

Due to the complexity of BN-structures and atomic bonding situations, the characterization of BN-phases by spectroscopic methods (e.g., IR and Raman) is difficult. It is not possible to identify BN phases using only one analytical method. For example, the X-ray diffraction peaks of c-BN correspond to those of Cu, Ni, and many other cubic phases. Elemental composition must be known or measured to be sure that no other phases are present. 

Some data for analytical characterization are summarized in the following sections (Fig. 8). 

Infrared spectroscopy (IR) or Fourier transform infrared spectroscopy (FTIR) are often used to characterize BN products. If pure BN mixtures with B N ratio of 1 1 are analyzed, it will be easy to distinguish between h-BN and c-BN. However, if the chemical composition of the sample is unknown, many artifacts can occur and a clear statement is often not possible. 

To identify c-BN, the characteristic transverse optical mode (TO) at 1065 cm-1 and longitudinal optical mode (LO) at 1340 cm-1 have been described [56]. When investigating commercial c-BN, commonly only one IR-peak between 1050 and 1100 cm-1 is observed. 

The situation is more complex for h-BN, t-BN, and a-BN, because all of them show peaks between 780 and 1370 cm-1, which makes it impossible to distinguish among these phases. 

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