Machinable semi-sintered boron-doped diamond as a heater for high pressure experiments

Internal resistance heaters in multi-anvil high pressure experiments often suffer from strong X-ray absorption or limited temperature capability. In this study, we report the synthesis of a machinable semi-sintered boron-doped diamond (BDD) that can be used as an X-ray-transparent heating element. The material was synthesized from diamond powder and amorphous boron under vacuum (1473–1573 K, 0.5–9 h) after cold isostatic pressing (180-200 MPa, 5 min). This porous BDD compact can be readily machined into thin-walled cylindrical heaters (down to 0.15 mm thick) using standard CNC machining. High pressure experiments up to ∼25 GPa demonstrate apparent temperatures exceeding ∼3000 K. In addition, in-situ synchrotron X-ray observations confirm that, unlike fully dense BDD heaters, the semi-sintered BDD does not degrade pressure generation efficiency. Performing comparably to conventional TiB2 heaters but with significantly higher X-ray transparency, semi-sintered BDD proves to be a highly promising heater for in-situ synchrotron X-ray observations under extreme pressure-temperature conditions.