Crystal structure of lutetium aluminate (LUAM), Lu4Al2O9

The crystal structure of the title compound containing lutetium, the last element in the lanthanide series, was determined using a single crystal prepared by heating a pressed pellet of a 2:1 molar ratio mixture of Lu 2 O 3 and Al 2 O 3 powders in an Ar atmosphere at 2173 K for 4 h. Lu 4 Al 2 O 9 is isostructural with Eu 4 Al 2 O 9 and composed of Al 2 O 7 ditetrahedra and Lu-centered six- and sevenfold oxygen polyhedra. The unit-cell volume, 787.3 (3) Å 3 , is the smallest among the volumes of the rare-earth ( RE ) aluminates, RE 4 Al 2 O 9 . The crystal studied was refined as a two-component pseudo-merohedric twin.