Effect of Co addition on the lattice parameter, electrical conductivity and sintering of gadolinia-doped ceria

Co-sintering aid has been added to Ce1.9Gd0.1O1.95 (CGO) by treating a commercial powder with Co(NO3)2 (CoCGO). X-ray diffraction (XRD) measurements of lattice parameter indicated that the Co was located on the CGO particle surface after calcination at 650 °C. After heat treatment at temperatures above 650 °C, the room temperature lattice parameter of CGO was found to increase, indicating redistribution of the Gd. Compared to CGO, the lattice parameter of CGO+2 cation% Co (2CoCGO) was lower for a given temperature (650–1100 °C). A.C. impedance revealed that the lattice conductivity of 2CoCGO was enhanced when densified at lower temperatures. Transmission electron microscopy (TEM) showed that, even after sintering for 4 h at 980 °C, most of the Co was located at grain boundaries.