LiIn2SbO6: A New Rutile-Related Structure Type with Unique Ion Channels

Single crystals of LiIn2SbO6 (LIAO) have been synthesized using a Li2MoO4 flux and characterized with X-ray diffraction. The compound crystallizes in a new structure type with a rutile-related framework. Like others in the rutile-related family, LIAO is formed of chains of edge-sharing octahedra. The chain structure, with a width that alternates between single and double octahedra, has not previously been reported in a rutile-related material. The framework is formed via corner sharing by the chains in a checkerboard arrangement, with Li+ residing in tetrahedral sites in the resulting, identically-alternating channels. Solid-state 6/7Li NMR spectroscopy and ab initio spectral calculations verify the presence of tetrahedrally coordinated lithium. The solution determined here contradicts previous reports of this material as a cation-ordered variant of LiSbO3. The relationship between this new structure and LiSbO3 and others in the rutile-related family is discussed. Variable temperature powder X-ray diffraction and diffuse reflectance show that LIAO has high thermal stability and a large direct band gap of 3.9 eV. AC impedance spectroscopy reveals that LIAO is a relatively poor Li conductor, displaying a conductivity of 1.3 × 10–7 S/cm at 623 K, along with an activation energy for charge transport of 1.1 eV. This material presents an opportunity to explore a new subfamily of rutile-related materials in which alternating-width chains may provide an independent avenue for tuning desired properties.