Crystal growth of new perovskite and perovskite related iridates: Ba3LiIr2O9, Ba3NaIr2O9, and Ba3.44K1.56Ir2O10

Single crystals of Ba₃LiIr₂O₉, Ba₃NaIr₂O₉, and Ba_3.44K_1.56Ir₂O₁₀ were grown from hydroxide fluxes. Ba₃LiIr₂O₉ and Ba₃NaIr₂O₉ form in the 6H–BaTiO₃ or triple perovskite structure, which is derived from the hexagonal and cubic stacking of AO₃] layers. The structure contains face-sharing Ir₂O₉ octahedra pairs, which are connected via corner shared LiO₆ (NaO₆) octahedra. Both compounds crystallize in the space group P6₃/mmc, Z=2, with a=5.7804(4) and c=14.302(1) and a=5.866(4) and c=14.596(1) for the Li and Na member, respectively. The structure of Ba_3.44K_1.56Ir₂O₁₀ is derived from the stacking of AO₃] and mixed A₂O] layers, and is an n=3 member of the A_nM_n?1O_3n]A₂O] family of hexagonal perovskite related oxides. The structure of Ba_3.44K_1.56Ir₂O₁₀ consists of (Ba₃Ir₂O₉) slabs separated by (Ba,K)₂O] layers and is isostructural with Ba₅Ru₂O₁₀. The (Ba₃Ir₂O₉) slabs contain isolated, face-sharing Ir₂O₉ octahedra pairs. The compound crystallizes in the space group P6₃/mmc, Z=2, with a=5.91330(1) Å and c=18.1792(7) Å. The magnetic moments determined from the temperature dependence of the magnetic susceptibility are low for all three oxides, which is thought to be due to a combination of spin–orbit coupling and strong exchange interactions within the iridium octahedra pairs.