Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 720, Issue -, Pages 460-465Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2017.05.278
Keywords
X-ray diffraction; Ionic conduction; Solid-state electrolyte; Li-batteries; Percolative phenomena
Categories
Funding
- MINECO [MAT2013-46452-C4-3-R, MAT2016-78362-C4-3-R]
- CAM government (MATERYENER 3CM) [P2013/MIT-2753]
- European Commission [247579]
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The synthesis by solid state reaction of new fast ion conductors with perovskite structure was carried out. The crystal structure and electric properties of the La1/2+1/2xLi1/2-1/2xTi1-xAlxO3 (0 <= x <= 1) solid solution were investigated by powder X-ray diffraction and impedance spectroscopy. All compositions of the La1/2Li1/2TiO3-LaAlO3 system, exhibited a single cubic perovskite structure (ac approximate to 3.87-3.79 angstrom; SG Pm-3m). The progressive decrease in the unit cell parameters agrees with the lower ionic radii of Al3+ in relation to Ti4+, which are allocated in the same octahedra. An upward deviation from the lineal ideal solid solution behavior described by Vegard's law was observed and it was tentatively associated with a volume excess created by solid dilution of non-isovalent cations. Structural features were deduced from Rietveld analysis of XRD patterns. Ti(Al)O-6 octahedra are regular and La/vacancies are randomly distributed in A-site of the perovskite. The conductivity decreased almost four orders of magnitude with the Li content. This important decrease on the conductivity was attributed to the charge carrier (Li+) decrease and the blockade of the perovskite conduction pathways by La ions, according to a three dimensional percolative process. In consequence we present here a new example of percolative system of ionic conductors and the results confirm the important role played by effective vacant A-sites, n(eff) = [Li] + n(A), on Li conductivity of this fast ion conductors family with perovskite structure. (C) 2017 Elsevier B.V. All rights reserved.
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