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

A lithium cobalt germanate compound (Li(2)CoGeO(4)) 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 (GeO(4))(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 Li(2)CoGeO(4) 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.