Direct Evidence of Catalytic Role of Boron in Graphite-to-Diamond Solid-Phase Conversion under High Pressure

Herein experimental evidence on the catalytic role of boron in the conversion of graphite to diamond is presented. Highly ordered graphite with up to 1.5% of carbon atoms substituted with boron is obtained from a mixture of nanoglobular carbon and amorphous boron at 5.0 GPa and 1400-1700 degrees C. It transforms completely into heavily boron-doped diamond at a pressure of 7.5-8.0 GPa and temperature of 1600-1650 degrees C, which is well below the melting temperature of boron-carbon eutectic.