High Temperature And High Pressure Synthesis Study Of BC₃

Materials are treated by high pressure and high temperature might have excellent properties than those obtained at normal conditions, such as, extreme hardness, high thermal and chemical stability, et al. People show great interest to search superhard multi-function materials under high temperature and high pressure. At present, the widely used superhard materials are mainly diamond and cubic BN. The shortcomings of these materials limited their application. Recently, the discovery of superconductivity in polycrystalline boron-doped diamond (BDD) synthesized under high pressure and high temperature. Theoretical calculation shows that the higher boron content the higher superconducting transition temperature will be. In addition, boron doped in some metals have been discovered. Boron-carbon compounds could have higher superconducting transition temperature for its high boron content. Diamond-like BC and diamond-like BC_1.6 have been synthesized under high pressure and high temperature. Another big success is the superhard diamond-like BC₅. Theoretical calculation shows that it Vickers hardness is , and 500 K more thermally stable than nanocrystalline diamond at the same grain size, and its Tc could be as high as 45 K. The 1:3 boron-to-carbon ratio (graphite-like BC₃) has been absorbed people's attention with higher boron content according to the diamond like-BC₅, could exist new atomic structure with the extreme hardness, and higher superconducting transition temperature.In this paper, we used a modified Merrill–Bassett-type our-screw diamond anvilcell (DAC) with a 400μm culet in this study. A hole of 120μm was drilled for the sample chamber on Steel T301 gasket. NaCl was used as pressure transmitting media and heat insulation. Raman scattering was used to study the BC₃ phase under high pressure and high temperature, a direct transformation from the graphite-like BC₃ to a new BC₃ phase was observed experimentally in a diamond-anvil cell at high temperature 1700±20K, 1800±20K , 1900±20K and high pressure 30.5, 40.5 and 50.5GPa. We shut out the possibility that BC₃ decomposed into other boron-carbon, or boron and carbon compounds under high pressure and high temperature, and we are sure that the new compound is not all the boron-carbon compounds that have been known until now by the comparison of all boron-carbon Raman spectra. We have obtained a new structure of BC₃ after a series of laser heating high pressure and high temperature experiments. In order to confirming the new BC₃ structure, the theoretical Raman spectrum of s-BC₃ at 0GPa was computed and compared to our experimental by the collaborators. The most simulated intensive peak positions and relative intensities of s-BC₃ match our experimental observation very well. Electronic and electron-phonon coupling calculations reveal s-BC₃ is a superconductor with critical temperature 7K. Furthermore, the hardness of this phase is 46.8GPa, so the s-BC₃ is a candidate of superhard superconducting multifunctional materials.