Download citation
Download citation
link to html
A-site cationic ordered LaBaCo2O6−δ and disordered La0.5Ba0.5CoO3−δ perovskite phases were obtained by solid state reaction. Their structural properties were studied at room temperature and 673 K, by combining powder diffraction techniques, X-ray diffraction and neutron powder diffraction with an independent determination of the oxygen content of the samples by thermogravimetry. La0.5Ba0.5CoO3−δ exhibits cubic symmetry with cations randomly distributed, whereas LaBaCo2O6−δ shows tetragonal symmetry with the La3+ and Ba2+ ions distributed in alternating layers. The diffraction data were analyzed using the Rietveld method and different structural and microstructural models. Bond valence and Fourier methods were used to determine bond distances and neutron/electron density maps. LaBaCo2O6−δ exhibits a higher concentration of oxygen vacancies than La0.5Ba0.5CoO3−δ, because the O atom is weakly bonded to the LaO layers. The anisotropic atomic displacement and the neutron density distribution suggest a two-dimensional O-migration path for LaBaCo2O6−δ and a three-dimensional path for La0.5Ba0.5CoO3−δ.The mechanism of electrical conductivity is via electron holes with high mobilities (μLa0.5Ba0.5CoO3−δ = 2.49 cm2 V−1 s−1 and μLaBaCo2O6−δ = 1.48 cm2 V−1 s−1 at room temperature) and low activation energy (EaLaBaCo2O6−δ  = 0.019 eV and EaLa0.5Ba0.5CoO3−δ = 0.030 eV). It has also been found that the higher electronic and ionic conductivities in La0.5Ba0.5CoO3−δ compared to those in LaBaCo2O6−δ are due to the higher dimensionality of transport and to greater overlapping between the Co 3d and O 2p orbitals.

Supporting information

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S1600576713031233/fs5049sup1.pdf
Details of structures, refinement and Fourier maps analysis

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600576713031233/fs5049sup2.cif
Contains datablocks global, La0.5Ba0.5CoO3-493K

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600576713031233/fs5049sup3.cif
Contains datablocks global, La0.5Ba0.5CoO3-673K

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600576713031233/fs5049sup4.cif
Contains datablocks global, LaBaCo2O6-493K

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600576713031233/fs5049sup5.cif
Contains datablocks global, LaBaCo2O6-673K

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup6.rtv
Contains datablock LaBaCo2O6-XRD

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup7.rtv
Contains datablock LaBaCo2O6-673K-NPD

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup8.rtv
Contains datablock LaBaCo2O6-293K-NPD

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup9.rtv
Contains datablock La0.5Ba0.5CoO3-XRD

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup10.rtv
Contains datablock La0.5Ba0.5CoO3-673K-NPD

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600576713031233/fs5049sup11.rtv
Contains datablock La0.5Ba0.5CoO3-293K-NPD

Computing details top

Program(s) used to refine structure: FULLPROF.

(La0.5Ba0.5CoO3-493K) top
Crystal data top
Cubic, Pm3mV = 58.93 (1) Å3
Hall symbol: -P 4 2 3Constant Wavelength Neutron Diffraction radiation
a = 3.89151 (5) Å
Data collection top
Radiation source: nuclear reactor2θmin = 0.297°, 2θmax = 160.247°, 2θstep = 0.050°
Refinement top
Rp = 4.367χ2 = NOT FOUND
Rwp = 5.9474001 data points
Rexp = 2.84734 parameters
RBragg = 2.3080 restraints
Crystal data top
Cubic, Pm3mV = 58.93 (1) Å3
a = 3.89151 (5) ÅConstant Wavelength Neutron Diffraction radiation
Data collection top
2θmin = 0.297°, 2θmax = 160.247°, 2θstep = 0.050°
Refinement top
Rp = 4.367χ2 = NOT FOUND
Rwp = 5.9474001 data points
Rexp = 2.84734 parameters
RBragg = 2.3080 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Co0.500000.500000.500000.0031 (6)*
La0.000000.000000.000000.0055 (4)*0.50000
Ba0.000000.000000.000000.0055 (4)*0.50000
O0.500000.500000.000000.0176 (5)*0.96977

Experimental details

Crystal data
Chemical formula?
Mr?
Crystal system, space groupCubic, Pm3m
Temperature (K)?
a (Å)3.89151 (5)
V3)58.93 (1)
Z?
Radiation typeConstant Wavelength Neutron Diffraction
Specimen shape, size (mm)?, ? × ? × ?
Data collection
Diffractometer?
Specimen mounting?
Data collection mode?
Scan method?
2θ values (°)2θmin = 0.297 2θmax = 160.247 2θstep = 0.050
Refinement
R factors and goodness of fitRp = 4.367, Rwp = 5.947, Rexp = 2.847, RBragg = 2.308, χ2 = NOT FOUND
No. of parameters34

Computer programs: FULLPROF.

 

Follow J. Appl. Cryst.
Sign up for e-alerts
Follow J. Appl. Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds