Influence of compaction pressure on the impedance of Gadolinium Doped Ceria electrolytes for IT-SOFCs

Abstract

Gadolinium doped ceria (GDC) is one promising oxygen-ion conducting ceramic electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs), due to its high ionic conductivity at reduced operating temperatures, favorable defect chemistry, and compatibility with a broad range of electrode materials [1,2]. Despite extensive understanding of its intrinsic ion transport mechanisms, the influence of ceramic processing parameters on the effective electrical behavior of polycrystalline GDC electrolytes remains an active topic for investigation [3-5]. In particular, processing steps that govern green body formation and sintering can strongly affect microstructural features such as density, grain size, grain boundary character, and residual porosity, which in turn determine the macroscopic conductivity [4-6]. In this work, dense GDC ceramic pellets were fabricated under systematically varied isostatic compaction pressures ranging from 49 to 140 MPa, followed by sintering at 1350 C for four hours under identical thermal conditions. Platinum electrodes were deposited on both sides of the pellets by electron-beam deposition, and the electrical properties were characterized by electrochemical impedance spectroscopy (EIS) over a wide temperature range. The results demonstrate a dependence of the impedance with respect to compaction pressure.