High pressure behaviors and novel high-pressure phase of Si3N4 and TiN

Here we present synchrotron-based X-ray diffraction experiments combined with diamond anvil cell on the nitrogen-bearing compounds Si3N4 and TiN up to similar to 53 GPa and similar to 51 GPa, respectively. The pressure-induced phase transition of Si 3 N 4 is evidenced at 42.3 GPa at room temperature and a new monoclinic high-pressure phase assigned to the P2, Pm, or P2/m space group was observed. The pressure-volume relationship is well described by the third-order Birch-Mumaghan equation of state, which yields K-T0 = 271(4) GPa and K-T0' = 43 (2), and the anisotropic compression with M-c > M-a. is obtained. While TiN is stable up to 50.8 GPa without any evidence of phase transformation. Our results provide more information on the stability and elastic properties of nitrogen-bearing minerals in the Earth's mantle, and thus provide new insights for understanding the nitrogen stability and transport properties in the deep earth. (C) 2020 Elsevier B.V. All rights reserved.