Enhanced sintering of Ce0.8Nd0.2O2−δ-La0.8Sr0.2Ga0.8Mg0.2O3−δ using CoO as a sintering aid

Ce0.8Nd0.2O1.9 (NDC) and La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolytes were prepared using a sol-gel method. NDC-LSGM composite electrolytes were subsequently prepared by adding 5% (w, mass fraction) precalcined LSGM powders to NDC sols. The electrolyte materials of NDC-Co and NDC-LSGM-Co were obtained by adding 1 mol% CoO to NDC sols and NDC-LSGM composite electrolytes, respectively. The microstructure and phase composition of the pellets were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). The electrical conductivities of the pellets were measured using alternative current (AC) impedance spectroscopy. The results indicate that a single perovskite phase is observed for the LSGM ceramic, while NDC-Co, NDC-LSGM and NDC-LSGM-Co have a cubic fluorite structure similar to that of NDC. As a sintering aid, CoO can further promote grain growth and increase relative density (＞95%) of the NDC-LSGM composite electrolyte. The enhancement of the total conductivity is primarily attributed to the large increase in the conductivity of the grain boundary. However, the slight decrease of the grain boundary conductivity of the NDC-LSGM-Co electrolyte is caused by the presence of trace amounts of impurity phases in the grain boundaries.