Unravelling the synergistic effect on ionic transport and sintering temperature of nanocrystalline CeO2 tri-doped with Li Bi and Gd as dense electrolyte for solid oxide fuel cells

Microstructural and electrochemical investigations of tri-doped (Gd, Li and Bi) cerium oxide, with theoretical formula Ce0.8(1-x-y)Gd0.2(1-x-y)LixBiyO[1.9(1-x-y)+x/2+3y/2] (x = 0.02 or 0.03 and y = 0.03 or 0.02 and x + y = 0.05) were carried out by XRD, BET, SEM, Raman, and EIS analyses. According to the dilatometer analysis, the synergistic combination of lithium and bismuth promotes the reduction of sintering temperature down to 800-900 degrees C. A densification > 95% was achieved for the electrolytes sintered at 900 degrees C. Raman analysis, in agreement with XRD, demonstrated that the lithium and bismuth induced changes due to the growth of the topological disorder and a higher defectiveness provoked by doping. The high dopant concentration (5 mol%) is well distributed into the lattice and forms a complex network of defects that traps the oxygen vacancies and hence mobile ions promoting the ionic transport. As compared to a single (CGO) or a bi-doped system (BiCGO and LiCGO) an improvement of total conductivity was achieved at lower sintering temperature, with a maximum value for Ce0.76Gd0.19Li0.03Bi0.02O1.85 of 2.68.10(-3)-1.66.10(-1) S cm(-1) in temperature range of 400-800 degrees C. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Microstructural and electrochemical investigations were conducted on tri-doped cerium oxide with Gd, Li, and Bi. The combination of lithium and bismuth effectively reduced the sintering temperature. The doping-induced complex network of defects improved the ionic transport and increased the total conductivity.