Polycrystalline powders of La1-xSrxGa0.8Mg0.2O3-delta (LSGM) (x=0.05, 0.10, and 0.20) were synthesized using an alternative freeze-drying method. Precursors and sintered pellets of LSGM were characterized by X-ray diffraction and scanning electron microscopy, paying special attention to the temperature dependence of phase formation and microstructure evolution. The results of this study indicate that dense LSGM samples with a low level of Sr doping x < 0.1 can be prepared as a single phase at 1300 degrees C, although a temperature of 1400 degrees C is required for samples with a higher Sr content (x > 0.1). The phase formation and densification processes take place in a short time due to the small particle size and the low degree of agglomeration of the synthesized powders. Dense samples of La0.8Sr0.2Ga0.8Mg0.2O3-delta without secondary phases are obtained after sintering at 1400 degrees C for only 15 min with ionic conductivity values of 0.1 S/cm at 800 degrees C.