Pressure- and temperature-induced phase transition in the B–C system

A direct transformation from the g-BC1.6 phase to a diamondlike BC1.6 phase was obtained in a diamond-anvil cell at high temperature, 2230±140K, and high pressure, 45GPa. Such a transition has not been observed in the B–C system before. The recovered samples were examined using both synchrotron-based x-ray diffraction and confocal micro-Raman spectroscopy at ambient conditions. The lattice parameter of the diamondlike phase (3.5745Å) is close to that of diamond. The measured visible laser-excited Raman spectra of a diamondlike BC1.6 phase reveal a peak at 1315cm−1 which is attributed to the LO mode. It is also found that the orthorhombic/hexagonal phase was formed under high pressure in the areas where heating was not enough to make transformation in the cubic phase.