Effect of sintering on the ionic conductivity of garnet-related structure Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12} and In- and K-doped Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12}

Journal Article · Sat Apr 15 04:00:00 EDT 2006 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2005.12.025· OSTI ID:20784946

Thangadurai, Venkataraman ^[1]; Weppner, Werner ^[1]

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1. Chair for Sensors and Solid State Ionics, Faculty of Engineering, University of Kiel, Kaiserstr. 2, D 24143-Kiel (Germany)

Garnet-structure related metal oxides with the nominal chemical composition of Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12}, In-substituted Li{sub 5.5}La{sub 3}Nb{sub 1.75}In{sub 0.25}O{sub 12} and K-substituted Li{sub 5.5}La{sub 2.75}K{sub 0.25}Nb{sub 2}O{sub 12} were prepared by solid-state reactions at 900, 950, and 1000 deg. C using appropriate amounts of corresponding metal oxides, nitrates and carbonates. The powder XRD data reveal that the In- and K-doped compounds are isostructural with the parent compound Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12}. The variation in the cubic lattice parameter was found to change with the size of the dopant ions, for example, substitution of larger In{sup 3+}(r {sub CN6}: 0.79 A) for smaller Nb{sup 5+} (r {sub CN6}: 0.64 A) shows an increase in the lattice parameter from 12.8005(9) to 12.826(1) A at 1000 deg. C. Samples prepared at higher temperatures (950, 1000 deg. C) show mainly bulk lithium ion conductivity in contrast to those synthesized at lower temperatures (900 deg. C). The activation energies for the ionic conductivities are comparable for all samples. Partial substitution of K{sup +} for La{sup 3+} and In{sup 3+} for Nb{sup 5+} in Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12} exhibits slightly higher ionic conductivity than that of the parent compound over the investigated temperature regime 25-300 deg. C. Among the compounds investigated, the In-substituted Li{sub 5.5}La{sub 3}Nb{sub 1.75}In{sub 0.25}O{sub 12} exhibits the highest bulk lithium ion conductivity of 1.8x10{sup -4} S/cm at 50 deg. C with an activation energy of 0.51 eV. The diffusivity ('component diffusion coefficient') obtained from the AC conductivity and powder XRD data falls in the range 10{sup -1}-10{sup -7} cm{sup 2}/s over the temperature regime 50-200 deg. C, which is extraordinarily high and comparable with liquids. Substitution of Al, Co, and Ni for Nb in Li{sub 5}La{sub 3}Nb{sub 2}O{sub 12} was found to be unsuccessful under the investigated conditions.

• OSTI ID: 20784946
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 4 Vol. 179; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
CHEMICAL COMPOSITION
CUBIC LATTICES
DOPED MATERIALS
GRAIN BOUNDARIES
INDIUM IONS
IONIC CONDUCTIVITY
LANTHANUM COMPOUNDS
LANTHANUM IONS
LATTICE PARAMETERS
LITHIUM COMPOUNDS
LITHIUM IONS
NIOBIUM COMPOUNDS
NIOBIUM IONS
OXIDES
SINTERING
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
X-RAY DIFFRACTION