Neutron powder diffraction study of tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} with the garnet-related type structure

Journal Article · Fri Jan 15 04:00:00 EST 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.10.030· OSTI ID:21372465

Awaka, Junji ^[1]; Kijima, Norihito ^[1]; Kataoka, Kunimitsu ^[1]; Hayakawa, Hiroshi ^[1]; Ohshima, Ken-ichi ^[2]; Akimoto, Junji ^[1]

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1. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)
2. Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

We have successfully synthesized a polycrystalline sample of tetragonal garnet-related Li-ion conductor Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} by solid state reaction. The crystal structure is analyzed by the Rietveld method using neutron powder diffraction data. The structure analysis identifies that tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} has the garnet-related type structure with a space group of I4{sub 1}/acd (no. 142). The lattice constants are a=13.106(2) A and c=12.630(2) A with a cell ratio of c/a=0.9637. The crystal structure of tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} has the garnet-type framework structure composed of dodecahedral La(1)O{sub 8}, La(2)O{sub 8} and octahedral HfO{sub 6}. Li atoms occupy three types of crystallographic site in the interstices of this framework structure, where Li(1) atom is located at the tetrahedral 8a site, and Li(2) and Li(3) atoms are located at the distorted octahedral 16f and 32g sites, respectively. These Li sites are filled with the Li atom. The present tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} sample exhibits bulk Li-ion conductivity of sigma{sub b}=9.85x10{sup -7} S cm{sup -1} and grain-boundary Li-ion conductivity of sigma{sub gb}=4.45x10{sup -7} S cm{sup -1} at 300 K. The activation energy is estimated to be E{sub a}=0.53 eV in the temperature range of 300-580 K. - Graphical abstract: The crystal structure of tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} had the garnet-related type structure with a space group of I4{sub 1}/acd (no. 142) with the lattice constants of a=13.106(2) A and c=12.630(2) A. The tetragonal Li{sub 7}La{sub 3}Hf{sub 2}O{sub 12} had the fully ordered Li arrangement.

• OSTI ID: 21372465
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 183; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
CRYSTALS
DIFFRACTION
ENERGY
GARNETS
GRAIN BOUNDARIES
IONS
LATTICE PARAMETERS
LITHIUM IONS
MICROSTRUCTURE
MINERALS
NEUTRON DIFFRACTION
POLYCRYSTALS
SCATTERING
SILICATE MINERALS
SPACE GROUPS
SYMMETRY GROUPS
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TETRAGONAL LATTICES
X-RAY DIFFRACTION