DOE OSTI2020
Na5LaO4 is Spinel-like structured and crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. there are five inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two equivalent LaO4 tetrahedra, corners with six NaO4 tetrahedra, corners with four NaO4 trigonal pyramids, an edgeedge with one NaO4 tetrahedra, an edgeedge with one LaO4 tetrahedra, and edges with two NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.32–2.66 Å. In the second Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share corners with two equivalent NaO4 tetrahedra, corners with two equivalent LaO4 tetrahedra, corners with eight NaO4 trigonal pyramids, an edgeedge with one NaO4 tetrahedra, an edgeedge with one LaO4 tetrahedra, and edges with two NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.32–2.53 Å. In the third Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two equivalent LaO4 tetrahedra, corners with four NaO4 tetrahedra, corners with six NaO4 trigonal pyramids, an edgeedge with one LaO4 tetrahedra, edges with two NaO4 tetrahedra, and an edgeedge with one NaO4 trigonal pyramid. There are a spread of Na–O bond distances ranging from 2.33–2.52 Å. In the fourth Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 trigonal pyramids that share corners with two equivalent LaO4 tetrahedra, corners with four NaO4 tetrahedra, corners with six NaO4 trigonal pyramids, an edgeedge with one LaO4 tetrahedra, edges with two NaO4 tetrahedra, and an edgeedge with one NaO4 trigonal pyramid. There are a spread of Na–O bond distances ranging from 2.34–2.47 Å. In the fifth Na1+ site, Na1+ is bonded to four O2- atoms to form NaO4 tetrahedra that share corners with two equivalent NaO4 tetrahedra, corners with four equivalent LaO4 tetrahedra, corners with six NaO4 trigonal pyramids, an edgeedge with one NaO4 tetrahedra, and edges with three NaO4 trigonal pyramids. There are a spread of Na–O bond distances ranging from 2.39–2.44 Å. La3+ is bonded to four O2- atoms to form LaO4 tetrahedra that share corners with six NaO4 tetrahedra, corners with six NaO4 trigonal pyramids, an edgeedge with one NaO4 tetrahedra, and edges with three NaO4 trigonal pyramids. There are one shorter (2.28 Å) and three longer (2.30 Å) La–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one La3+ atom. In the second O2- site, O2- is bonded to five Na1+ and one La3+ atom to form a mixture of distorted edge and corner-sharing ONa5La octahedra. The corner-sharing octahedra tilt angles range from 53–58°. In the third O2- site, O2- is bonded to five Na1+ and one La3+ atom to form a mixture of distorted edge and corner-sharing ONa5La octahedra. The corner-sharing octahedra tilt angles range from 53–60°. In the fourth O2- site, O2- is bonded to five Na1+ and one La3+ atom to form a mixture of edge and corner-sharing ONa5La octahedra. The corner-sharing octahedra tilt angles range from 54–60°.