Ionic Conductivity and Microstructure of Sr- and Mg-doped LaGaO_3

Samples of Sr- and Mg-doped LaGaO3 (LSGM) were prepared by using a solid state reaction method. The conductivities of LSGM with various additions of Sr and Mg were dealt with. The results show that the ionic conductivities of LSGM increase with the increase of x or y at first, and after reaching a maximum, the ionic conductivities of LSGM decrease with the further increase of x or y. It can be seen that Sr- and Mg-doped LaGaO3 materials with the highest conductivity, σ=0.148S/cm at 800 ℃, are LSGM1520 and LSGM2015. For the two compositions, LSGM materials are composed of single phase-LaGaO3 without secondary phases. It can also be seen that ionic conductivities of LSGM increase with the increase of testing temperature and the curves of ln(σT) with 1/T reveal two straight lines intersecting at T*(T* is about 670 ℃) and activation energy of oxygen-vacancy motion at lower temperatures (T T*) is greater than that at higher temperatures (T T*).