Study on Performances of Transmitting Pressure and Measuring Pressure of [C4mim][BF4] by Using Spectroscopic Techniques
ZHU Xiang1, 2*, YUAN Chao-sheng1, CHENG Xue-rui1, LI Tao1, ZHOU Song1, ZHANG Xin1, DONG Xing-bang1, LIANG Yong-fu2, WANG Zheng2
1. College of Physics and Electronic Engineering, Zhengzhou University of Light Industry, Zhengzhou 450001, China
2. Henan Key Laboratory of Magnetoelectronic Information Functional Materials, Zhengzhou University of Light Industry, Zhengzhou 450001, China
Abstract：Diamond anvil cell (DAC) is a kind of high-pressure generator that is frequently used in the laboratory and plays an important role in the field of high-pressure research. When pressure-transmitting medium (PTM) in DAC can just provide non-hydrostatic pressure, it will be difficult to accurately measure the pressure of the sample by using the ruby fluorescence method. The same cases frequently emerge under ultra-high pressure conditions. If there is a material with dual functions of transmitting pressure and measuring pressure, the pressure values of the sample under non-hydrostatic conditions might be measured accurately according to the principle that the closer the positions are, the more similar the pressures are. Apparently, it is important to search for the material with dual functions of transmitting and measuring pressure. In this paper, a ruby particle and a small drop of ionic liquid [C4mim][BF4]were loaded into a DAC, a series of high-pressure environments were provided by compressing the [C4mim][BF4]. Simultaneously, the fluorescence spectrum of ruby and the Raman spectrum of [C4mim][BF4] was obtained under high pressures. By analyzing the positions of the R1 line of ruby, the pressure values of [C4mim][BF4] were obtained. By analyzing the widths of the R1 line of ruby, it was found that the hydrostaticand quasi-hydrostatic pressures provided by [C4mim][BF4] were in the ranges of 0~6.26 and 6.26~21.43 GPa, respectively. It could be speculated that [C4mim][BF4] can use as PTM in the pressure range of 0~21.43 GPa. In addition, [C4mim][BF4] is a liquid phase Ⅰ, liquid phase Ⅱ, amorphous phase I, and amorphous phase II in the ranges of 0~2.28, 2.28~6.26, 6.26~14.39, and 14.39~21.43 GPa, respectively. By analyzing the positions of ν(B-F) and ν(ring) as the characteristic Raman peaks from [C4mim][BF4], it was found that they followed linear changes with increasing pressure during the above four phases of [C4mim][BF4]. What’s more, the formulas of pressure and position of ν(B-F) and ν(ring) were given. The formulas are very important for [C4mim][BF4] to be a pressure gauge. To sum up, [C4mim][BF4] has the dual functions of transmitting pressure and measuring pressure and can use simultaneously as the PTM and the pressure gauge. The research results provided an important basis for accurate measurement of sample pressure in non-hydrostatic environments and provide a new solution to the inaccurate measurement of sample pressure under ultra-high pressure conditions.
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