Dynamics of Mn3+ in off-stoichiometric LiMn1.5Ni0.5O4

LiMn1.5Ni0.5O4 is investigated by anelastic spectroscopy in order to study the manganese dynamics. An intense thermally activated peak, detectable only in off-stoichiometric samples, is attributed to a polaronic conduction due to an electron transfer from Mn3+ to a Mn4+, and the consequent motion of the Jahn-Teller lattice distortion. In order to have a good fit of the experimental data, the Jonscher model for ionic dynamics is adopted for the first time in this spinel structure. A value of about 0.3 eV for the energy barrier of the polaronic conduction is obtained. (C) 2014 Elsevier B.V. All rights reserved.