For solid electrolytes in which ionic transport is effected by the diffusion of mobile point defects, one strategy for increasing the ionic conductivity is to increase the concentrations of the charge-carrying defect species through aliovalent doping , i.e., introducing dopant atoms with a formal valence that differs from that of the atoms being replaced. This difference in effective atomic charge causes a shift in the defect-formation equilibria for all charged native defects, which results in an increase, or decrease, in the concentrations of any charge-carrying vacancies or interstitials.