[S-IT14] Deep Earth Sciences

[SIT14-P10] Axial temperature gradients in experimental cells for high-pressure multi-anvil apparatus

*Takuya Moriguti¹, Akira Yoneda^1,2, Eiji Ito¹ (1.Institute for Planetary Materials, Okayama University, 2.Department of Earth and Space Science, Graduate School of Science, Osaka University)

Keywords:Temperature gradient, Multi-anvil, Coesite-stishovite transition, High-temperature, Cell design, Furnace materials

Based on SiO₂ phase transition between coesite and stishovite, the axial temperature gradient in experimental cell assembly with Re foil furnace for high-pressure multi-anvil apparatus was investigated at 2500ºC and at 10.4 – 12.4 GPa. The axial thermal profile showed parabolic curve, well approximated quadratically between the temperature differences from the center of the heater (ΔT) and the distance from the center (d; mm), ΔT = -213.5d² (r² = 0.99; correlation coefficient). This indicates the temperature gradient of 214 ºC/mm at 1mm from the hotspot (center of the heater) at 2500ºC heating. The axial thermal profiles of other typical cylindrical furnaces in previous works can be also well approximated by a quadratic function at <2000ºC heating except for that of the semiconductor furnace (boron-doped diamond furnace) at 3020ºC heating, which showed a quartic curve, ΔT = -5.00d⁴ - 0.69d² (r² = 1.00), using the data from numerical simulation in Yoneda et al. [1]. The thermal profile of the semiconductor furnace indicates the temperature gradient of 6 ºC/mm at 1mm from the hotspot. This significant reduction of the temperature gradient in the semiconductor furnace at ~500ºC higher heating temperature than that in Re furnace shown above would be due to the properties of electrical resistivity of the semiconductor which shows lower resistivities at higher temperatures. In this presentation, the factors of influences to temperature gradients in the cells such as the heating temperature, the shape and the material of the furnace, and the designs of the cell assembly are also discussed quantitatively comparing with the axial thermal profiles from previous works.

Reference
[1] Yoneda et al. (2014) High Press. Res. 34, 392-403.