IFISUR   23398
INSTITUTO DE FISICA DEL SUR
Unidad Ejecutora - UE
artículos
Título:
Effect of cationic order-disorder on the transport properties of LaBaCo2O6-d and La0.5Ba0.5CoO3-d perovskites
Autor/es:
D. GARCES; C. F. MARTINEZ SETEVICH; A. CANEIRO; G. CUELLO; L. V. MOGNI
Revista:
JOURNAL OF APPLIED CRYSTALLOGRAPHY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2014 vol. 47 p. 325 - 334
ISSN:
0021-8898
Resumen:
A-site cationic ordered LaBaCo2O6-d and disordered La0.5Ba0.5CoO3-d, perovskite phases were obtained by Solid State Reaction. Their structural properties were studied at room temperature and 400 °C combining powder diffraction techniques, XRD and NPD with an independent determination of the oxygen content of the samples by thermogravimetry. La0.5Ba0.5CoO3-d exhibits cubic symmetry with cations randomly distributed, whereas the LaBaCo2O6-d shows tetragonal symmetry with the La+3 and Ba+2 ions distributed in alternating layers. The diffraction data were analyzed using the Rietveld method and testing different structural and microstructural models. Bond Valence and Fourier methods were used to determine bond distances and neutron/electron density maps. The LaBaCo2O6-d presents higher concentration of oxygen vacancies than La0.5Ba0.5CoO3-d, because the O is weakly bonded to LaO layers. The anisotropic atomic displacement and the neutron density distribution suggest a two-dimensional O-migration path for LaBaCo2O6-d and a three-dimensional for La0.5Ba0.5CoO3-d.The mechanism of electrical conductivity is by electron-hole with high mobilities (𝜇La0.5Ba0.5CoO3−d= 2.49 cm2V−1s−1and 𝜇LaBaCo2O6−δ= 1.48 cm2V−1s−1 at room temperature) and low activation energy (𝐸𝑎𝐿𝑎𝐵𝑎𝐶𝑜2𝑂6−𝛿=0.019 𝑒𝑉 and 𝐸𝑎𝐿𝑎0.5𝐵𝑎0.5𝐶𝑜𝑂3−𝛿=0.030 𝑒𝑉). It has been also found that the higher electronic and ionic conductivities in La0.5Ba0.5CoO3-d compared to those in LaBaCo2O6-d, is due to the higher dimensionality of transport and to higher overlapping between Co-3d and O-2p orbital.