Sintering and electric conductivity of (Fe,Mn,Sm) codoped CeO_2-

Two ceria-based samples, Sm0.1Ce0.9O2 (ST00) and Fe0.005Mn0.005Sm0.09Ce0.9O2 (S9HH) were synthesized by EDTA-citrate method to achieve molecular-scale homogeneity. The solubility limits of the (Fe, Mn) dopants were determined by quantitative X-ray diffraction (QXRD). The microstructure of samples after sintering were analyzed by SEM and TEM. The conductivity was measured by 2-probe DC and AC impedance methods. The results showed no solubility limit of Mn and Fe with 5-9 mol% Sm in CeO2. Two ceria-based samples, ST00 and S9HH could be densified at 1,500 degrees C and 1,250 degrees C respectively in 1 h to full density. The electrical conductivity results showed that densified 9HH performed higher electrical conductivity at 800 degrees C, i.e. 7.15 x 10(-2) S.cm(-1) with an ionic transference ratio (t(i)) 0.76 at 600 degrees C. Sm-segregation near grain boundary was found in SDC, but amorphous submicron-domains in (Fe, Mn, Sm) co-doped grains were responsible for the ease of the sintering at 1,250 degrees C.