Discovery of a giant lattice in Mg₉₇Zn₁Yb₂ alloy

The Mg-rich corner of Mg–metal (M)–rare earth element (REE) ternary systems results in a long-period stacking-ordered (LPSO) phase that increases the strength and elongation of the Mg alloy. Using Yb at the REE position does not result in the LPSO phase; instead, it forms unique crystalline structures with intriguing properties. In this study, we found a new giant lattice belonging to the P6/mmc space group by quenching the Mg₉₇Zn₁Yb₂ alloy at 723 K. The giant lattice, which precipitates around the α-Mg matrix with a chemical composition of Mg₇₅Zn₇Yb₁₈ (at%), comprises a basic structure and a superlattice. We developed an atomic configuration model that expresses the basic structure as alternating stacking of three types of layers. The observed features indicate that the structure of the giant lattice is similar to that of the approximant quasicrystal reported for Mg–M–REE ternary systems.