La0.8Sr0.2Ga0.8Mg0.2O3(LSGM8282) and La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5) are two kinds of excellent electrolytes for intermediate temperature solid oxide fuel cells (ITSOFCs). LSGM8282 and LSGMC5 were prepared using solid state reaction in this study. Total electrical conductivities and electronic conductivities of LSGM8282 and LSGMC5 were comparatively studied using four-probe AC impedance spectrometry and Hebb-Wagner polarization. The results showed that the total electrical conductivity of LSGM8282 had no dependency on oxygen partial pressures. However, the total electrical conductivity of LSGMC5 increased with the decrease in oxygen partial pressures under high oxygen partial pressures. Within the temperature range of 973 similar to 1173 K, the orders of dependency of the electron conduction and hole conduction of LSGM8282 on the oxygen partial pressure was -1/4 and 1/4, respectively. Within the temperature range of 1073 similar to 1173 K, the orders of dependency of the electron conduction and hole conduction of LSGMC5 on the oxygen portial pressure was -1/4 and about 1/8, respectively. The oxygen ion conductivity of LSGM8282 had no dependency on oxygen partial pressures, while that of LSGMC5 increased with the decrease in oxygen partial pressures under high oxygen partial pressures
