X-Ray Diffraction Investigation of Lithium Silicides under High Pressure

Abstract

Lithium silicide Li₁₂Si₇ (orthorhombic) and Li₇Si₃ (trigonal), composed of Li ions and Si clusters were synthesized by heat treatment of Li and Si mixture. Their high-pressure properties were investigated by synchrotron X-ray diffraction (XRD) measurements using a diamond anvil cell (DAC). Compression was successfully made up to 16 GPa for Li₁₂Si₇ and 20 GPa for Li₇Si₃, but no phase transition was observed. The bulk modulus was obtained from the fitting by Murnaghan equation of state. The obtained bulk moduli were compared with those of other lithium silicides, Si and Li, and there were found to be correlation between the bulk modulus and the Li–Si composition ratio.