Heavily Boron Doped Diamond Powder: Synthesis and Rietveld Refinement

Boron-doped diamonds were synthesized by the reaction of an amorphous globular carbon powder (80%) with a powder of 1,7-di (oxymethyl)-M-carborane (20%) in a 'toroid'-type high-pressure chamber at a pressure of 8.0 GPa and temperature of 1700 degrees C. The structure was refined by the Rietveld method according to the X-ray powder diffraction data. It was shown that the unit cell parameters of these diamonds have two discrete quantities: around 3.570 angstrom for small concentrations of B (similar to 1-1.5%) and around 3.578 angstrom for large concentrations of B (similar to 2-3%). The concentration of the vacancies in the diamonds exceeds the concentration of boron atoms by 2-3 fold. This fact can play an important role in the formation of the structure and in determining the physical properties of diamonds.