Exploring the defect formation and ionic migration in A2Zr2O7 (A = La, Ce, Nd, and Gd) Pyrochlore solid-state electrolytes

This study investigated the potential of A2Zr2O7 2 Zr 2 O 7 pyrochlore phase oxides (A = La, Ce, Nd, and Gd) as solid oxide fuel cell (SOFC) electrolyte materials. A2Zr2O7 2 Zr 2 O 7 ceramics were synthesized using the sol-gel process, and their disordered pyrochlore structure was confirmed by X-ray Diffraction and Rietveld refinement. Field Emission Scanning Electron Microscopy (FE-SEM) was used to examine the morphology of the materials, while X-Ray Photoelectron Spectroscopy (XPS) confirmed a high oxygen ion concentration. UV-Vis Diffuse Reflectance Spectroscopy (DRS) and density of states calculations consistently showed similar bandgap patterns in all zirconate pyrochlore. Density Functional Theory (DFT) simulations provided insights into the electronic structure and migration pathways. A two-probe conductivity study confirmed the relation between the ionic conductivity and ordering degree of pyrochlore. At 750 degrees C, LZO, CZO, and GZO exhibited ionic conductivity values of 5.44 x 10-3-3 S/cm, 3.00 x 10-3-3 S/cm, and 2.01 x 10-3-3 S/cm respectively, while NZO demonstrated a conductivity of 1.27 x 10-2-2 S/cm at 700 degrees C, which is higher than that of the other samples. This study favours the use of the solgel route for processing zirconate pyrochlore materials, highlighting its ability to achieve high densities at lower temperatures and exhibit enhanced ionic conductivity. A2Zr2O7 2 Zr 2 O 7 has emerged as a promising oxide-ion conducting solid electrolyte for intermediate temperature SOFC applications within the 600-750 degrees C temperature range.