Synthesis of boron-doped diamond and its application as a heating material in a multi-anvil high-pressure apparatus

Abstract

We developed methods to use synthesized boron-doped diamond (BDD) as a heater in a multi-anvil high-pressure apparatus. The synthesized BDD heater could stably generate an ultra-high temperature without the issues (anomalous melt, pressure drop, and instability of heating) arising from oxidation of boron into boron oxide and graphite-diamond conversion. We synthesized BDD blocks and tubes with boron contents of 0.5-3.0 wt. % from a mixture of graphite and amorphous boron at 15 GPa and 2000 °C. The electrical conductivity of BDD increased with increasing boron content. The stability of the heater and heating reproducibility were confirmed through repeated cycles of heating and cooling. Temperatures as high as ∼3700 °C were successfully generated at higher than 10 GPa using the BDD heater. The effect of the BDD heater on the pressure-generation efficiency was evaluated using MgO pressure scale by in situ X-ray diffraction study at the SPring-8 synchrotron. The pressure-generation efficiency was lower than that using a graphite-boron composite heater up to 1500 tons. The achievement of stable temperature generation above 3000 °C enables melting experiments of silicates and determination of some physical properties (such as viscosity) of silicate melts under the Earth's lower mantle conditions.

Formation of bridgmanite-enriched layer at the top lower-mantle during magma ocean solidification

“…Major limitations encountered in previous works of the same type were technical difficulties to perform the ultrahigh temperatures (more than~2500 K) that required to melt the silicate phases entirely and the difficulties to measure the extremely low viscosity of silicate melts at high pressure, requiring very fast radiographic measurements [10][11][12] . By using a new type of furnace made of boron-doped diamond 13 and ultrafast camera (frame rate reaches 1000 f/s), we could perform viscosity measurements up to 30 GPa and 3250 K. We investigated the viscosity of melts with compositions similar to major mantle minerals, namely forsterite (Mg 2 SiO 4 , Fo), enstatite (MgSiO 3 , En), and diopside (CaMgSi 2 O 6 , Di). Measurements have been performed slightly above the melting temperatures (see Methods section, Supplementary Table 1).…”

“…As heater, we used graphite or boron doped diamond (BDD) at pressures lower or higher than 8 GPa, respectively. The BDD heater can generate temperature as high as~4000 K with highly X-ray transparency, which is ideal to perform in-situ falling sphere viscometry at high pressures in multi-anvil apparatus 13 . The accurate determination of the falling-sphere terminal velocity in low-viscosity melts requires the use of ultra-fast camera (1000 fps) coupled with synchrotron X-ray radiography 11,12 .…”

Resistivity, Seebeck coefficient, and thermal conductivity of platinum at high pressure and temperature

“…By using sintered diamond cubic anvils, the maximum pressure reaches more than 120 GPa [53]. For high-temperature generation, a boron-doped diamond heater enables us to heat the sample to ∼4000 K [54]. Indeed, such a high-pressure and high-temperature condition corresponds to the region where the Seebeck coefficient exhibits strong pressure dependence.…”

“…The Seebeck coefficient is insensitive to pressure at the temperature below 1500 K. However, above 1500 K, the Seebeck coefficient exhibits strong pressure dependence. Recent technical developments of multianvil high-pressure experiments can generate over 120 GPa [53] and ∼4000 K [54]. In such high-pressure and -temperature conditions, special calibration is needed for the temperature measurements using the Pt-Rh thermocouple.…”

TiC-MgO composite: an X-ray transparent and machinable heating element in a multi-anvil high pressure apparatus

“…However, they are not suitable for in situ X-ray observations because of their low X-ray transparency. Recently, Xie et al [7] developed boron-doped diamond (BDD) heater, which is very refractory and X-ray transparent. However, owing to its hardness, it is hard to machine, making the production of tubular heaters out of BDD difficult.…”