Hebb-Wagner polarization technique was applied to Fe-doped SrTiO3 single and bicrystals: as far as a single crystal is concerned, the polarization is complicated by additional internal redox reactions, and it has to be appropriately generalized; as far as a bicrystal is concerned, it was demonstrated how the electronic and ionic partial conductivities of a grain boundary can be separated with this technique. The partial conductivities and the charge carrier concentrations thus obtained clearly demonstrate that the electronic and the ionic charge carriers are depleted in the space charge region, more specifically that the depletion of the ionic ones is more pronounced, being in agreement with the double charge of oxygen vacancies.