Synthesis and Ionic Conductivity of Lanthanum-based Ceria Ce1−xLaxO2−δ Electrolytes for Solid Oxide Fuel Cell Applications

Abstract

In advanced low temperature solid oxide fuel cell (LT-SOFC) technology, we present a comprehensive study on the effects of lanthanum co-substitution in ceria electrolyte. Using a co-precipitation synthesis approach, we successfully incorporated trivalent La ions into the ceria matrix to improve its structural and functional properties. This study investigates La3+ doped CeO2 solid electrolytes (LDC) synthesis and characterization at varying concentrations (0.2, 0.3, 0.4, and 0.5). The materials were characterized using a suite of analytical techniques. X-ray diffraction (XRD) analysis revealed that all samples maintained a cubic fluorite-type structure with evident changes in peak intensity and broadening as La3+ ion concentration increased, indicative of induced lattice defects FT-IR spectra indicated minor modifications in the Ce-O bond vibrational modes. Optical studies demonstrated enhanced absorption in the UV region and a consistent band gap of 3.15 eV across all samples, underscoring the doping's influence on electronic transitions. Scanning electron microscopy (SEM) images highlighted increased grain sizes and improved interparticle connectivity, which is essential for material performance. X-ray fluorescence spectroscopy verified the existence of cerium and lanthanum, proving the successful addition of dopants. Raman spectroscopy also confirmed changes in the structure, indicating alterations in the characteristic vibrational frequencies and a decrease in their intensity as the dopant concentration increased. The conductivity of the material was tested at low temperatures ranging from 573 K to 873 K for use in Solid Oxide Fuel Cells, with the highest conductivity recorded at 0.21 mS/cm at 873 K.