Dielectric relaxations in NASICON-type Li1.25Zr1.75Al0.25(PO4)3 solid electrolyte

Abstract

In this work, the conduction and relaxation behavior of lithium-ion conducting monoclinic Li[Formula: see text]Zr[Formula: see text]Al[Formula: see text](PO[Formula: see text] (LZAP) ceramic prepared via sol–gel method was investigated. Rietveld refinement of the X-ray diffraction data confirmed the structure of LZAP as monoclinic with space group [Formula: see text]21/[Formula: see text] at room temperature. The permittivity data were fitted using a modified Cole–Cole equation containing the complex conductivity terms to rationalize the giant dielectric constant and loss factor observed at lower frequencies. In addition, fittings revealed the presence of two thermally activated dielectric relaxations processes in LZAP ceramics, which were attributed to the lithium ions movement within the grain and grain boundary confines. The activation energies computed from the Arrhenius fitting of relaxation times associated with the grain and grain boundary regions were [Formula: see text]0.447 ± 0.009 eV and [Formula: see text]0.46 ± 0.01 eV, respectively. The activation energies for grain and grain boundary Li[Formula: see text] conduction were also found to have similar values ([Formula: see text]0.42 eV for grain, and 0.46 eV for grain boundary).