Electrical and dielectric properties of lithium manganate nanomaterials doped with rare-earth elements

Substituted LiRxMn2-xO4 (R=La3+, Ce3+, Pr3+ and x = 0.00 - 0.20) nanoparticles are prepared by the sol-gel method and the consequent changes in their lattice structure, dielectric and electrical parameters are determined by XRD, ED-XRF, SEM, LCR meter bridge and dc electrical resistivity measurements. Diffraction data show that the samples are single-phase spinel materials with crystallites sizes between 21 and 38 nm. The lattice parameter, cell volume and X-ray density are found to be affected by doping the Li-manganate with the rare-earth elements. The ED-XRF analysis confirms the stoichiometric composition of the synthesized samples and SEM reveals their morphology. Calculated values of the dielectric constant (epsilon') and the dielectric loss (tan delta) decrease with the frequency of the applied field. This is attributed to Maxwell-Wagner polarization. Replacement of manganese by the rare-earth elements results in an improvement in the structural stability of the material, which is considered to be useful for enhancement of the cycleability of the compounds when used in lithium rechargeable batteries, and increases significantly the values of k and tan 3 (except for Ce). Lithium manganate nanomaterials with high epsilon' and low tan delta may be attractive for application in memory storage devices. (c) 2008 Elsevier B.V. All rights reserved.