Microstructure and electrical conductivity of Ce0.9Gd0.1O1.95-MgO composite electrolyte

Ce0.9Gd0.1O1.95 (GDC)-xMgO (x = 0, 10%, 20%, 30%, 40%, 50 mol%) powders were synthesized by sol-gel method and then the corresponding composite ceramics were sintered in air atmosphere at 1500 °C for 5 h. The sintered samples consist of both GDC and MgO phases on the condition of x ≥ 10%, and the MgO grains segregate at the grain boundaries of GDC. As the MgO content rises from 0 to 20%, the average grain size of GDC decreases from 2.15 to 0.41 μm. The introduction of MgO can improve the specific grain boundary electrical conductivity of GDC-xMgO composite ceramics dramatically. The GDC-20%MgO shows the highest specific grain boundary conductivity, which is 1.726 × 10−5 S/cm at 400 °C, 9.16 times higher than that of pure GDC. The variation in the real total conductivity confirms that the formation of GDC/MgO heterogeneous interfaces is beneficial to the enhancement in the electrical conduction properties of GDC-xMgO composite ceramics.