Effect of the dopant nature on the conductivity of oxygen overstoichiometric oxyapatites with controlled microstructures

► Apatite electrolytes with high densities and controlled grain sizes were elaborated. ► Best ionic conductivities are obtained with the Mg doped apatite. ► The key parameter governing the conduction properties is the oxygen excess content. ► A new oxygen interstitial position was confirmed into the La(6h) channels. ► The higher conductivity of the Mg doped sample is correlated to structural parameters.