Development of Semiconductor Diamond Heater and Generation of Ultra-high Temperature of ~4,000 K under High Pressure
October 12(Thu), 2017
A joint research group of Okayama Univ., Ehime Univ., and JASRI succeeded in generating ultra-high temperature of ~4,000 K by using diamond-based semiconductor as a heating element under high pressure, which is ~1,000 K higher than the highest temperature achieved in the past researches. The joint group consisted of Associate Professor Akira Yoneda and Longjian Xie (JSPS research fellow) at the Institute for Planetary Materials (IPM), Okayama University, Professor Tetsuo Irifune at Geodynamics Research Center (GRC), Ehime University, and Yuji Higo, research scientist at SPring-8, a synchrotron X ray facility in Japan.
The research results were published in a science magazine issued by the American Institute of Physics, Review of Scientific Instruments, on September 22, 2017.
The earth’s deep interior is extremely high pressure and high temperature (Fig.1). At the core-mantle boundary (CMB) at 2,900 km depth, pressure reaches 136 GPa, and temperature is estimated to be ~4,000 K. HACTO, or the high-pressure group at IPM, succeeded in reaching 120 GPa, which is very close to the CMB pressure. On the other hand, high temperature generation has been limited to ~3,000 K owing to the limitation of heating element used under high pressure. HACTO conceived of diamond-based semiconductor as the best heating element, and started the project around 2011. With support provided by GRC at Ehime University (Fig. 2) and SPring-8, HACTO has demonstrated the superiority of the diamond-based semiconductor heater.
Diamond-based semiconductor consists of carbon (C) and boron (B) with low atomic number and high X-ray transmissivity. This feature enables us to conduct the falling sphere measurement for viscosity of silicate melts (Fig. 3). HACTO has started another project of generating ultra-high temperature by using the diamond semiconductor heater under pressure of ~100 GPa (Fig. 1).
The D” layer of 200-300 km thickness just above the CMB has been considered as the most important layer in the earth interior (Fig. 1). In the layer, bridgmanite with the perovskite structure transforms to the post-perovskite structure. HACTO’s next mission is to conduct the structural, compositional, and rheological Mineral Physics Study on the D” layer.
Highlights of the Research Results
- Diamond converts to semiconductor by doping boron (B). HACTO generated ultra-high temperature up to ~4,000 K under ultra-high pressure by using the diamond-based semiconductor as a heating element.
- Semiconductor diamond grains was pulverized by using the nano-polycrystalline diamond mortar at GRC, Ehime University (Fig. 2).
- Another important advantage of diamond semiconductor heater is its high X-ray transmissivity. This feature is very advantageous for the falling sphere method to measure viscosity of silicate melt by using synchrotron X-ray at SPring-8 (Fig. 3).
URL of HACTO: http://www.misasa.okayama-u.ac.jp/~hacto/top_e.html
Figure 1 Pressure-Temperature range capable in the Kawai type apparatus (KMA) in comparison with the earth interior. The present achievement of the semiconductor diamond heater enables us to conduct experimental study covering the whole mantle temperature condition toward the geotherm as indicated by the red arrow.
Figure 2 Photograph of nano-polycrystalline diamond (NPD, or, Hime-diamond) mortar. The hardest mortar in the world.
Snapshots of a falling sphere experiment. Elapsed times after the onset of melting are shown at the top of each snapshot. We can recognize that rhenium (Re) sphere dropped at a constant rate after 20 ms, which enables us to determine viscosity of the melt.
Journal: Review Scientific Instruments
Title: Synthesis of boron-doped diamond and its application as a heating material in a multi-anvil high-pressure apparatus
Authors: Longjian Xie, Akira Akira Yoneda,Takashi Yoshino, Daisuke Yamazaki, Noriyoshi Tsujino, Yuji Higo, Yoshinori Tange, Tetsuo Irifune, Toru Shimei & Eiji Ito
Year of Publication: 2017
Okayama University Silicon Valley Office (OUSVO)
Contact: Mototaka Senda, Ph.D.
- boron-doped diamond, nano-polycrystallin