Sound velocity and Equation of State of B4C*

B₄C, a light weight, impact-resistant, hard material, is used in a variety of applications that exploit these unique properties. However, the material fragments on high-velocity impacts, and laboratory studies provide evidence for pressure-induced amorphization. Si-doping in B₄C has been shown to delay the amorphization to higher pressures. To understand this high-pressure performance of B₄C, we performed ultrasonic and x-ray diffraction measurements under pressure using several techniques.  Using a Paris-Edinburgh cell to investigate the structural and elastic properties of B₄C to 7 GPa, we found that the longitudinal acoustic wave increases first with pressure, then flattened above 3 GPa. Complementary x-ray diffraction measurements provided a direct determination of the P-V-T equation of state of both B₄C and Si-doped B₄C to 3 GPa and 1200 K.