[S-IT03_29AM1] Structure and dynamics of Earth and Planetary deep interiors

[SIT03-07] Semiconductor diamond heater (SCD): An innovation for ultrahigh temperature experiments in the Kawai cell

*XIE Longjian¹、ITO Eiji¹、YONENDA Akira¹ (1.Institute for Study of the Earth Interior , Okayama University)

キーワード：Semiconductor Diamond Heater, Ultrahigh Temperature, Kawai Cell

We developed the semi-conductor diamond heater in the Kawai high pressure cell. The starting material of the semi-conductor diamond heater is born(B)-doped burned-graphite. We succeeded to improve the machinability of the B-doped burned-graphite by decreasing porosity. Following is the motivation and the background of the semi-conductor diamond heater project. It is important to generate extremely high temperature (~3000 ℃) in a large sample volume (~0.1mm³) in the Kawai apparatus.X-ray transparency is also desirable for in-situ synchrotron analysis. However, any traditional heater used in the Kawai apparatus so far does not satisfy the both requirements simultaneously. Semiconductor diamond is a candidate material to generate temperatures higher than 3000℃ with low x-ray absorption. Anton Shatskiy (2009) have generated a temperature of 3500℃ by using the semiconductor diamond heater in a large-volume Kawai-type high-pressure apparatus, although their temperature measurement is questionable from a viewpoint of the power-temperature relation. Furthermore, their semi-conducted diamond heater, made of boron and graphite powders, was not machinable and difficult to control the temperatures. It often became unstable at around 1000~1300℃and impossible to generate higher temperature.Systematic experiments have done to improve the performance of the semiconductor heater. We used a machinable block of graphite contain 3 wt.% boron as the starting material for the semi-conductor diamond heater. The graphite-diamond transformation started at ~1000-1200℃ at 15 GPa in the Kawai apparatus. After the transformation, we stably generated temperature to 2000 ℃. Activation energy of B-doped diamond is about 0.1 eV, which is much lower than that of pure diamond (5.45eV).References:Anton Shatskiy, Daisuke Yamazaki, Guillaume Morard, Titus Cooray, Takuya Matsuzaki et al. , Review of Scientific Instruments 80, 023907 (2009).