Samples of Sr- and Mg-cloped LaGaO3 (LSGM) with various concentrations of Sr and Mg were prepared by using solid-state reaction method. Results show that ionic conductivities increase with the increase of relative densities. It can also be known that the optimized concentration in La1-xSrxGa1-yMgyO3-0.5(x+y) with high conductivity is LSGM1520 or LSGM2015. The results also show that, in various concentrations of LSGM, equiaxed, rode-like, polygonal secondary phases such as LaSrGaO4 or LaSrGa3O7 were detected besides (La,Sr)(Ga,Mg)O-3 by means of SEM and EDX. With the increase of doped elements, i.e. x + y, the grain size increases. (c) 2006 Springer Science + Business Media, Inc.