Trends in Bulk Compressibility of Mo_2–xW_xBC Solid Solutions

The Mo2–xWxBC system is of interest as a material with high hardness while maintaining moderate ductility. In this work, synchrotron diffraction experiments are performed on Mo2–xWxBC solid solutions, where x = 0, 0.5, and 0.75, upon hydrostatic compression to ∼54 GPa, ∼55 GPa, and ∼60 GPa, respectively. Trends in bulk modulus, K0, are evaluated by fitting collected pressure–volume data with a third-order Birch–Murnaghan equation of state, finding K0 = 333(9) GPa for Mo2BC, K0 = 335(11) GPa for Mo1.5W0.5BC, and K0 = 343(8) GPa for Mo1.25W0.75BC. While K0 seems to express a slight increase when Mo is substituted by W, calculated zero-pressure unit cell volume, V0, exhibits the opposite trend. The decrease in V0 corresponds to an increase in valence electron density, hardness, and K0. Observations align with previously reported computational results and will inform future efforts to design sustainable materials with exceptional mechanical properties.