Thermal stimulated polarization and depolarization currents of LaF₃, undoped and CaF₂ doped, were obtained: They confirm on one hand conductivity data obtained by Murin et all. (9). On the other hand they prove the electrolytic nature of the conductivity. They show finally that Ca²⁺-anion vacancy complexes, capable of reorientation, are formed with an activation energy of reorientation of about 0.19eV.