Experimental study of the crystal structure of the Mg15 − xZnxSr3 ternary solid solution in the Mg–Zn–Sr system at 300 °C

Highlights: • Diffusion couples and alloys methods were designed for Mg_15−xZn_xSr₃ compound investigation. • The solid solubility limit of the Mg_15−xZn_xSr₃ (0.24 ≤ x ≤ 10.58) ternary solid solution was determined. • The crystal structure of Mg_15−xZn_xSr₃ phase was determined to be hexagonal structure with Ni₁₁Si₄Sc₃ prototype. • The fractional atomic occupancy of 6h, 6g, 4f, 2b and 12k sites of Mg_15−xZn_xSr₃ were functioned. - Abstract: A new ternary compound, Mg_15−xZn_xSr₃ with extensive solid solubility in the Mg–Zn–Sr system was observed and studied using electron probe microanalysis (EPMA), scanning electron microscopy SEM, and X-ray techniques. The solid solubility limits of this compound were found to be Mg_15−xZn_xSr₃ (0.24 ≤ x ≤ 10.58, at.%) at 300 °C using a diffusion couple and several equilibrated alloys. Analysis of the X-ray diffraction (XRD) patterns was carried out by Rietveld method. XRD data has shown that this solid solution crystallizes in the hexagonal P6₃/mmc (194) space group with the Ni₁₁Si₄Sc₃ prototype. The lattice parameters decrease linearly with decreasing Mg content indicating substitutional solid solubility. The fractional atomic occupancy of the 6h, 6g, 4f, 2b and 12k sites of this compound are function of Mg content.