title: Cation Miscibility and Lithium Mobility in NASICON Li1+xTi2-xScx(PO4)3(0 ≤ x ≤ 0.5) Series: A Combined NMR and Impedance Study.
abstract: Rhombohedral NASICON compounds with general formula Li1+xTi2-xScx(PO4)3(0 ≤ x ≤ 0.5) have been prepared using a conventional solid-state reaction and characterized by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and impedance spectroscopy. The partial substitution of Ti4+by Sc3+and Li+in pristine LiTi2(PO4)3increases unit-cell dimensions and the number of charge carriers. In Sc-rich samples, the analysis of XRD data and6Li/7Li,31P, and45Sc MAS NMR spectra confirms the presence of secondary LiScO2and LiScP2O7phases that reduce the amount of lithium incorporated in the NASICON phase. In samples with x < 0.3, electrostatic repulsions between Li ions located at M1 and M3 sites increase Li mobility. For x ≥ 0.3, ionic conductivity decreases because of secondary nonconducting phases formed at grain boundaries of the NASICON particles (core-shell structures). For x = 0.2, high bulk conductivity (2.5 × 10-3S·cm-1) and low activation energy (Ea= 0.25 eV) measured at room temperature make Li1.2Ti1.8Sc0.2(PO4)3one of the best lithium ionic conductors reported in the literature. In this material, the vacancy arrangement enhances Li conductivity.
authors.affiliation: Laboratoire d'Application de la Chimie aux Ressources et Substances Naturelles et à l'Environnement (LACReSNE), Université de Carthage, Faculté des Sciences de Bizerte , 7021 Zarzouna, Bizerte, Tunisia.
authors.forename: Radhouene
authors.initials: R
authors.lastname: Kahlaoui
authors.affiliation: Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciónes Científicas (CSIC) , Cantoblanco, 28049 Madrid, Spain.|Department of Materials and Environment (Microlab), Faculty of Civil Engineering & Geosciences, Delft University of Technology , Delft, The Netherlands.
authors.forename: Kamel
authors.identifier: http://orcid.org/0000-0002-4630-438X
authors.initials: K
authors.lastname: Arbi
authors.affiliation: Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciónes Científicas (CSIC) , Cantoblanco, 28049 Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sobrados
authors.affiliation: Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciónes Científicas (CSIC) , Cantoblanco, 28049 Madrid, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Jimenez
authors.affiliation: Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciónes Científicas (CSIC) , Cantoblanco, 28049 Madrid, Spain.
authors.forename: Jesus
authors.initials: J
authors.lastname: Sanz
authors.affiliation: Laboratoire d'Application de la Chimie aux Ressources et Substances Naturelles et à l'Environnement (LACReSNE), Université de Carthage, Faculté des Sciences de Bizerte , 7021 Zarzouna, Bizerte, Tunisia.
authors.forename: Riadh
authors.initials: R
authors.lastname: Ternane