Crystal Chemistry of LuPd₂O₄ and Other Spinel-Related NdCu₂O₄−LaPd₂O₄-Type Compounds

Abstract

Lutetium palladium oxide (LuPd 2 O 4 ) has been prepared in a multianvil apparatus at 60 kbar pressure and 1000 °C. It crystallizes in the tetragonal LaPd 2 O 4 -type structure with space group I 4 1 /a, a = 5.681(1) Å, c = 9.881(2) Å, and Z = 4. The structure of this compound, like that of NdCu 2 O 4 and other members of this new class, is closely related to that of spinel except for the difference in oxygen arrangements, leading to a difference in coordination of the A, B, and O ions. It can be derived from spinel by oxygen displacements. A new version of Kugimiya and Steinfink's AB 2 O 4 correlation map in the region 0.04 < K ab < 0.18 and 0.8 < r a /r b < 1.7, has been generated. It shows that the new AB 2 O 4 class lies in the area between the spinel- and CaFe 2 O 4 -type regions.