Sm 2 − x AE x Ti O 5 − x 2 samples, with AE alkaline earth metal (Ca, Sr or Mg) were synthesized by a combustion method. The substitution limit of Ca into Sm 2 TiO 5 was found to be x = 0. 15, while for Sr single phase was obtained for only x = 0.03 and for Mg; no single phase was clearly obtained. The impedance measurements under dry and wet atmospheres (air and 5% H 2 – Ar) probed the protonic and electronic conductivity contributions at low and high temperatures, respectively, to the total conductivity of Sm 2 TiO 5. The Ca and Sr doped samples exhibited an increase in conductivity compared to the parent compound, with the Ca doped samples showing the highest values. The Sm 1.85 Ca 0.15 TiO 4.925 sample displayed the highest conductivity, 4.36 × 10 −4 S cm −1 , at 900 °C. This value represented an improvement of around one order of magnitude compared to the undoped sample (3.58 × 10 −5 S cm −1 ). The activation energy values obtained from the Arrhenius plot of the total conductivity of all the samples (under ambient air) ranged between 0.94 and 1.38 eV. • Cuspidine oxides Sm 2 TiO 5 have been doped to introduce oxide ion vacancies. • Sm 1.85 Ca 0.15 TiO 4.925 showed highest oxide ion conductivity of 0.5 mS cm −1 at 900 °C. • Conductivity increases a little at over 600 °C in reducing atmospheres due to limited electronic conduction. • Conductivity increases a little at below 600 °C in humidified atmospheres due to contribution from protonic conduction.
Chavez-Cardenas et al. (Mon,) studied this question.