Synthesis, optical and ionic conductivity studies of a lithium cobalt germanate compound

Abstract

A lithium cobalt germanate compound (Li₂CoGeO₄) was synthesized and studied. The X-ray powder diffraction pattern demonstrated a monoclinic crystal system with the Pn space group. The morphology and composition were done by scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). A vibrational study confirmed the existence of the anion (GeO₄)⁴⁻ and its vibrations. The estimated value of the direct band gap (E_g) was evaluated at 3.45 eV. The measurements of the electrical properties were performed in the frequency interval from 100 Hz to 1 MHz and the temperature range from 553 K to 663 K. The Nyquist plots revealed the existence of a single semicircle in all impedance spectra due to the grain interior effect. The AC electrical conduction in Li₂CoGeO₄ has been explained through several processes, which can be coupled with two different formalisms. The complex electric modulus studies M*(ω) confirmed that the relaxation process is thermally activated.