Solid-state synthesis of boron subnitride, B6N: myth or reality?

Solid-state synthesis of boron subnitride, B 6 N, as a result of chemical interaction between boron and boron nitride at 7.5 GPa and 1700 °C has been previously reported by Hubert et al. However, a critical analysis of the results has shown that the evidence for the formation of boron subnitride with B 6 O-like structure is inconclusive. We have studied in situ the interaction between boron and BN at the same p – T conditions using X-ray diffraction with synchrotron radiation. At 7.4 GPa and 1700 °C the formation of a new phase has not been observed. At the same time, HP–HT treatment has resulted in strong and unpredictable preferred orientation of boron crystallites. This leads to the rise of some weak boron reflections that might be erroneously attributed to the appearance of a new phase. .