Dielectric relaxation in pure and Co-doped Bi12GeO20 single crystals

We report the results of investigation of dielectric spectroscopy study of single crystals of Bi12GeO20 and Bi12GeO20 doped with Co nanoparticles. The complex dielectric constant was measured in the temperature interval from 5 to 450K and frequencies from 1Hz to 1 MHz. The electrical conductivity of both samples was thermally activated with potential barriers of 0.55 eV and 0.59 eV, respectively. Doped samples had bigger complex dielectric constants and sigma' exhibited slightly steeper temperature dependence than in the pure sample. The dielectric relaxation was observed in pure and doped single crystals and relaxation frequencies showed similar activation energies as electrical conductivities.