New honeycomb iridium(v) oxides: NaIrO3 and Sr3CaIr2O9

Abstract

We report the structures and physical properties of two new iridates, NaIrO₃ and Sr₃CaIr₂O₉, both of which contain continuous two-dimensional honeycomb connectivity. NaIrO₃ is produced by room temperature oxidative deintercalation of sodium from Na₂IrO₃, and contains edge-sharing IrO₆ octahedra that form a planar honeycomb lattice. Sr₃CaIr₂O₉, produced via conventional solid-state synthesis, hosts a buckled honeycomb lattice with novel corner-sharing connectivity between IrO₆ octahedra. Both of these new compounds are comprised of Ir⁵⁺ (5d⁴) and exhibit negligible magnetic susceptibility. They are thus platforms to investigate the origin of the nonmagnetic behavior exhibited by Ir⁵⁺ oxides, and provide the first examples of a J = 0 state on a honeycomb lattice.