Electric conductions in La0.9Sr0.1GaO3−δ and La0.9Sr0.1Ga0.9Mg0.1O3−δ

Abstract Electric conductions in La 0.9 Sr 0.1 Ga 1− x Mg x O 3− δ (LSGM; x =0 and 0.1) have been elucidated by ac and dc methods as a function of temperature. Using complex-plane impedance analyses and dielectric relaxation processes along with dc results, activation energy for electric conduction, migration energy of O 2− ions ( E M ), and energy required to create a free mobile oxygen vacancy which assists O 2− migration ( E O ) within intragrains and in boundaries have been obtained separately. Dielectric dispersion due to a distribution of relaxation times in boundaries is observed. The activation energy for each electric conduction is nearly equal to sum of E M and E O . Lattice distortion due to a large difference in ionic radii of Mg 2+ and Ga 3+ brings about high migration energy within intragrains in x =0.1 specimen compared with that of x =0. Such high migration energy has an adverse effect on improvement of ionic conductivities but excess oxygen vacancies compensate this adverse effect. In boundaries, disturbances in coulombic potential fields due to disordered ionic arrangements discourage ionic conductions.