Crystal structure of the quaternary lithogallate Sr${}_2$LiGaO${}_4$

The new quaternary lithogallate Sr${}_2$LiGaO${}_4$ was prepared by conventional solid-state synthesis in a welded tantalum ampoule at T = 850 °C. Single-crystal X-ray diffraction was used to elucidate the crystal structure of the compound, which crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 11.2434(4), b = 5.6879(2), and c = 6.6983(2) Å. The phase composition of the powder sample was determined by Rietveld refinement based on X-ray diffraction data. The crystal structure is composed of layers of corner-sharing LiO${}_4$ and GaO${}_4$ tetrahedra with alternating orientation parallel to the crystallographic bc plane. The eightfold coordinated strontium atoms are arranged in a zigzag manner between the layers forming two types of double-capped trigonal prismatic SrO${}_8$ units with common faces. The crystal structure of Sr${}_2$LiGaO${}_4$ is isotypic to that of the lithoaluminate derivate Sr${}_{1.85}$Ba${}_{0.15}$LiAlO${}_4$.