Raman spectra based pressure calibration of the non-gauge sapphire anvil cell at high temperature and high pressure

Abstract

Gem anvil cell is on important tool in high pressure experimental research, and the key of its application is the accurate calibration of the pressure in sample chamber. To date, the pressure has been routinely calibrated by the extra gauge such as ruby. This may increase the difficulty in building a setup and changing the chemical environment, even chemical reaction happens with the sample, thereby degrading the experimental results. In this study, using the synthesized pale sapphire and the heatable Zha-Bassett type cell, the relationships between Raman shift of sapphire-anvil interface and the pressure, and also temperature in chamber are investigated by the confocal Raman microscope at 0-6.3 GPa and 300-573 K, which is used to establish a non-gauge sapphire anvil cell system. The result shows that the pressure induced Raman shift of sapphire anvil at room temperature is 1.6443 cm-1/GPa and the temperature induced shift at room pressure is -0.0198 cm-1/K. We fit the experimental data at simultaneous high temperature and high pressure (HTHP) and find that: ∂ν12/∂T=-0.01913-0.00105×P, ∂ν12/∂P=1.9158-0.00105×T. The effect between the pressure and temperature can be described by ∂ν12/∂P∂T=-0.00105. After this calibration: P=(Δλ-0.01913×ΔT)/(1.9158-0.00105×ΔT), the pressure in the sample chamber can be calculated by the Raman shift of the interface of anvil cell in the HTHP experiment, which can be directly used in hydro-thermal reaction system and has great importance in physics, material science and geoscience.