The Indium Subnitrides Ae6In4(In x Li y )N3- z (Ae = Sr and Ba)

The indium nitrides Sr6In4(In0.32Li0.92)N2.49 and Ba6In4.78N2.72 have been synthesized from an excess of molten sodium. They crystallize in a stuffed variant of the η-carbide structure type in the cubic space group Fd3̄m with Z = 8. The lattice parameters are a = 14.3752(4) and 15.216(1) Å, with cell volumes 2970.6(2) and 3523.3(6) Å3, respectively. In both compounds there are vacancies on some of the indium and nitrogen sites and, in the case of Sr6In4(In0.32Li0.92)N2.49, mixed lithium−indium occupancy of one metal site. It is demonstrated that the partial and mixed occupancies act to carefully tune to electron count to almost fulfill the bonding requirements of the stellar quadrangular subnets of both compounds. Four probe resistivity measurements performed upon a pellet of Sr6In4(In0.32Li0.92)N2.49 show it to have a room-temperature resistivity of 6.3 mΩ·cm with a weak temperature dependence.