Book excerpt: The advancement of material engineering over the last few decades has allowed for the development of modern metallic and ceramic construction materials, composites, nanomaterials and various kinds of coatings with desired performance characteristics. They form the basis for the development of the automotive industry, the aviation industry, the chemical equipment industry, etc. They can function in ever higher temperatures and aggressive environments. On the other hand, the advancement of electronics requires the development of new and cheaper materials: semiconductors, insulators, materials with magnetic, ferrimagnetic or piezoelectric properties, etc. The desired properties of materials or their surface layers depend on chemical composition, dopants, and the concentration of point defects, through which the transport of ions and electrons takes place. The functional properties also depend on the nuances of production technologies which allow to obtain a specific texture and a desired concentration of ionic and electronic point defects. The monograph follows up on the issues related to the concentration of charge carriers in pure and doped oxides. Based on the diagrams of the concentration of point defects, the calculation results of the concentration of charge carriers and their mobility are presented, using the results of the studies on the electrical conductivity and the thermoelectric power in some specific oxides of 3d metals. In turn, the results of calculations of the ionic defect diffusion coefficients, conducted using the coefficients of self-diffusion and chemical diffusion as well as the concentration of ionic defects in these oxides, are presented. The given material will be useful to a wide range of researchers and developers of new materials with a wide range of required properties.