Boron-doped diamond synthesized at high-pressure and high-temperature with metal catalyst

Abstract

The boron-doped diamond (BDD) powder consisting of 40–100µm particles was synthesized at 5GPa and 1500–1600°C from a mixture of 50wt% graphite and 50wt% Ni–Mn catalyst with an addition of 1wt% or 5wt% boron powder. The size of crystal domains of doped and non-doped diamond was evaluated as a coherent scattering region by X-ray diffraction (XRD) and using small-angle neutron scattering (SANS), being ≥180nm (XRD) and ~100nm (SANS). Magnetic impurities of NiMnx originating from the catalyst in the synthesis, which prevent superconductivity, were detected by magnetization measurements at 2–300K. X-ray photoelectron spectroscopy, the temperature dependence of the resistivity, XRD, and Raman spectroscopy reveal that the concentration of electrically active boron is as high as (2±1)×1020cm−3 (0.1at%). To the best of our knowledge, this is the highest boron content for BDD synthesized in high-pressure high-temperature process with metal catalysts.