Semiconductor diamond heater in the Kawai multianvil apparatus: an innovation to generate the lower mantle geotherm

Abstract

Semiconductor diamond is considered the best heater material to generate ultra-high temperatures in a Kawai cell. In two pioneering studies, a mixture of graphite and amorphous boron (or boron carbide, B 4 C) was converted to semiconductor diamond in the diamond stability field and was confirmed to generate 2000°C and 3500°C, respectively. Following these works, we synthesized a homemade boron-doped graphite block with fine machinability. With this technical breakthrough, we developed a semiconductor diamond heater in a smaller Kawai-type cell assembly. Here, we report the procedure for making machinable boron-doped graphite, and the performance of the material as a heater in a Kawai cell at 15 GPa using tungsten carbide anvils and at ∼ 50 GPa using sintered diamond anvils. Furthermore, we present a finite element simulation of the temperature distribution generated by a semiconductor diamond heater, which is much more homogeneous than that generated by a metal heater.

Simultaneous generation of ultrahigh pressure and temperature to 50 GPa and 3300 K in multi-anvil apparatus

“…The BDD heater was originally developed using a graphite-boron composite as a precursor that converts to BDD in situ during the heating process. [14][15][16][17] Later developments focused on the pre-sintered BDD heater, which has a better heating performance due to the avoidance of graphite-to-diamond conversion. For example, a BDD heater synthesized at high pressure and temperature expanded the temperature range to 4000 K at 15 GPa.…”