I've read that electron doping in certain materials can lead to higher permittivity (for example, Nb in TiO2). This is a little confusing to me, as permittivity decreases with conductivity (see http://en.wikipedia.org/wiki/Permittivity#Lossy_medium). Can anyone explain this to me? P.S.: Both the dielectric constant and dielectric loss appear to increase with the case I mentioned above. I can understand the loss term increasing, but not the overall dielectric constant.