High-pressure high-temperature behavior of polymer derived amorphous B-C-N

Dense diamond-like BCN compounds are of interest due to their extreme hardness and predicted excellent thermal and chemical stability, which are superior to those of diamond and c-BN. Here, we report on the high-pressure high-temperature (HP-HT) behavior of amorphous BC₂N and BC₄N -as potential precursors for HP-HT synthesis of diamond-like BCN. Prepared via hydroboration reaction of piperazine borane and pyridine borane, respectively, amorphous BC₂N and BC₄N are characterized by well-mixed B-N, C-C and C-N bonds, confirmed by XPS analysis. These BCN compositions were subjected to pressures between 5-12 GPa and temperatures up to 1700 °C using multi-anvil apparatus and toroid-type press. In- and ex-situ X-ray diffraction reveals the decomposition of BC₄N to graphite and h-BN between 5 and 12 GPa above 500 °C, in contrast to BC₂N which remains amorphous up to 1600 °C.