High-pressure synthesis and low-temperature thermal expansion behavior of homogeneous phosphorus-rich pseudo-binary compound (V0.5Cr0.5)P4

Abstract

A black phosphorus layered homogeneous phosphorus-rich compound – (V0.5Cr0.5)P4 is synthesized using a large volume press under conditions of P = 5 GPa, 1100 °C, and 1 h of heating. (V0.5Cr0.5)P4 has a monoclinic (C2/c) structure with lattice parameters and cell volume of a = 5.2307(3)Å, b = 10.861(4)Å, c = 5.8253(4)Å, β = 110.784°, and V = 309.41(4)Å3, respectively. The thermal expansion behavior above about 110K has been investigated by low-temperature synchrotron XRD. The coefficient of thermal expansion, α, was calculated to be αa = 0.57 × 10−5K−1, αb = 0.70 × 10−5K−1, αc = 0.92 × 10−5K−1, αβ = 0.13 × 10−5K−1 and αv = 2.10 × 10−5K−1 at 293K. This thermal expansion behavior presents an anisotropic expansion characteristic different from pure black phosphorus due to the V/Cr atom that bonded the black phosphorus layers together.