Synthesis and Characterization of Gadolinium-Doped Zirconia as a Potential Electrolyte for Solid Oxide Fuel Cells

Abstract

Zirconia-based composites with high thermochemical stability and electrochemical activity are the most promising solid electrolytes for manufacturing solid oxide fuel cells (SOFCs). In the present work, nanocrystalline composite powders of gadolinium-doped zirconia (GDZ: Gd2xZr2(1−x)O4−x) with various doping fractions (0.01 ≤ x ≤ 0.16) were synthesized by the Pechini method and applied for the fabrication of several electrolyte pellets to evaluate their physicochemical properties, sinterability, and conductivity. The X-ray diffraction (XRD) patterns and the thermogravimetry/differential thermal analysis (TGA/DTA) of the synthesized powders confirmed the successful formation of nanocrystalline GDZ in the tetragonal phase with complete substitution of gadolinium phase into the zirconia (ZrO2) lattice. The synthesized gadolinium zirconate powders were then shaped into pellet forms using the tape casting method, followed by sintering at 1300 °C (for 2.5 h). The microstructural analysis of the electrolyte pellets showed suitable grain boundary welding at the surface with an acceptable grain growth at the bulk of the T-phase GDZ samples. The impedance measurements indicated that the T-phase GDZ-8 could provide a comparably higher ionic conductivity (with 7.23 × 10−2 S/cm in the air at 800 °C) than the other dopant fractions. The results of this work can help better understand the characteristics and electrochemical performance of the T-phase gadolinium zirconate as a potential electrolyte for the fabrication of SOFCs.

Highly Conductive Cerium- and Neodymium-Doped Barium Zirconate Perovskites for Protonic Ceramic Fuel Cells

“…However, its high chemical affinity towards the atmospheric gases or any acidic compounds (CO 2 , SO 2 , and H 2 O), under practical electrochemical systems, can create undesired by-products of carbonates and hydroxides, which results in the alteration of the cerate phase, respectively [6,7]. On the other hand, the latter electrolyte, BaZrO 3 , offers excellent chemical 2 of 14 stability under various acidic and atmospheric gases [7][8][9]. However, it delivers a lower conductivity than that of sintered BaCeO 3 pellets as reasoned by its significant grain boundary resistance [10,11].…”