One step synthesis and conductivity of alkaline and rare earth co-doped nanocrystalline CeO2 electrolytes

Gadolinia doped ceria (GDC) was co-doped with SrO (Sr–GDC), Pr2O3 (Pr–GDC) and doubly co-doped with SrO and Pr2O3 (Sr–Pr–GDC) and their effects on the electrical conductivity were studied. 20 mol% gadolinia doped ceria and the co-doped compositions were processed in one step by solution combustion synthesis. X-ray diffraction (XRD) analysis confirmed the presence of a single cubic phase in the processed powders. The powders were found to be nanocrystalline in nature by transmission electron microscopy (TEM). A high relative density (≥94%) was obtained in the sintered pellets at lower sintering temperatures compared to microcrystalline ceria powders. SrO co-doping helped achieving a higher sintered density owing to low melting point of Sr. The relative density of GDC, Pr–GDC, Sr–GDC and Sr–Pr–GDC was 94.2%, 94%, 96.6% and 96.1% respectively. Ionic conductivity of the sintered pellets was measured using AC two-probe impedance spectroscopy. Both Sr and Pr co-doping resulted in considerable improvement in the conductivity of GDC. The doubly co-doped composition (Sr–Pr–GDC) exhibited higher conductivity compared to GDC, Pr–GDC and Sr–GDC.