Synthesis and investigation of the morphological, optical, electrical and dielectric characteristics of a disodium cobalt orthogermanate.

A sodium cobalt germanate material (Na 2 CoGeO 4 ) was synthesized and studied. The X-ray powder diffraction pattern revealed a monoclinic crystal system with the Pn space group. The calculated value of the direct bandgap ( E g ) was (3.89 ± 0.02) eV. Electrical measurements were undertaken in a frequency range from 40 Hz to 1 MHz and a temperature range from 403 K to 573 K. Nyquist plots revealed only a semicircle in the whole impedance spectra due to the effect of interior grains. The AC conductivity of Na 2 CoGeO 4 was associated with the correlated barrier hopping (CBH) model. Studies of the complex electric modulus M *( ω ) confirmed that the relaxation process was thermally activated.