Zn as sintering aid for ceria-based electrolytes

Gd-doped ceria (CGO) nanopowders were mixed with up to 1 mol% of Zn (as nitrate) to exploit the role of this dopant on sintering and electrical performance. All samples were prepared by two-step sintering schedules to try to combine the advantages of both effects on low-temperature densification. Structural and microstructural analyses were complemented with impedance spectroscopy (wide range of temperatures and oxygen partial pressures) and ion-blocking measurements. The combination of all data suggests that Zn is preferentially located in the grain boundary region, playing a significant role on sintering. Zn additions (1 mol%) allowed for a 100 °C lower sintering temperature with respect to pure CGO. A marginal effect on the oxide-ion conductivity and a small enhancement (less than 20%) in n-type electronic conductivity was found between Zn-free and 1 mol% Zn-doped CGO. The removal of Zn from CGO after sintering is discussed.