Investigation on the crystal structure and mechanical properties of the ternary compound Mg11-xZnxSr combined with experimental measurements and first-principles calculations

A new ternary compound, Mg11-xZnxSr in the Mg-Zn-Sr system was observed and studied using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscope (EDS), X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The XRD patterns were refined by the Rietveld refinement method and the results revealed that the crystallized Mg11-xZnxSr phase belonged to tetragonal I41/amd space group and had the Cd11Ba prototype. The Mg atoms were successfully doped into Zn11Sr crystal lattice by occupying Zn atomic sites. Moreover, the Rietveld refinement and computational results demonstrated a gradual decrease in the a-axis and c-axis lattice parameters with decreasing concentration levels of Mg coordination substitution in the lattice of Mg11-xZnxSr compound. The elastic constants and modulus of the Mg11-xZnxSr compounds calculated by first-principles calculations (FPC) indicated they were increased with the increasing of Zn content. The variation of hardness, d-band widths and the total density of states for Mg11-xZnxSr compounds with Zn content was discussed.