Experimental investigation and modelling of the Na+ mobility in NaLnTiO4 (Ln = La, Nd) ceramics

Abstract

Abstract In NaLnTiO 4 (Ln = La, Nd) layered perovskite-like compounds, the mobility of sodium ions was studied using impedance spectroscopy and simulated by the molecular dynamics approach. NaLnTiO 4 was prepared via a high-temperature solid-state reaction with final annealing at 900 °С. The conductivity was measured using the complex impedance technique between 1 MHz and 100 Hz in the temperature range of 523–923 K. Using the DFT (Density Functional Theory) method, the charges of atoms in the crystal structure were calculated and applied to simulate the sodium atom mobility in NaNdTiO 4 and NaLaTiO 4 crystals using classical molecular dynamics in the temperature range of 523–923 K. Based on these calculations, the dependence of the diffusion coefficients of sodium atoms on temperature was studied. The mobility of sodium ions in NaLaTiO 4 is demonstrated to be higher than that in NaNdTiO 4 because of the more ionic characteristic of its bonds.