Structural Diversity of Rare-Earth Oxychalcogenides

Mixed-anion systems
have garnered much attention in the past decade
with attractive properties for diverse applications such as energy
conversion, electronics, and catalysis. The discovery of new materials
through mixed-cation and single-anion systems proved highly successful
in the previous century, but solid-state chemists are now embracing
an exciting design opportunity by incorporating multiple anions in
compounds such as oxychalcogenides. Materials containing rare-earth
ions are arguably a cornerstone of modern technology, and herein,
we review recent advances in rare-earth oxychalcogenides. We discuss
ternary rare-earth oxychalcogenides whose layered structures illustrate
the characters and bonding preferences of oxide and chalcogenide anions.
We then review quaternary compounds which combine anionic and cationic
design strategies toward materials discovery and describe their structural
diversity. Finally, we emphasize the progression from layered two-dimensional
compounds to three-dimensional networks and the unique synthetic approaches
which enable this advancement.