Gadolinium-Doped Ceria (GDC) is a prospective material for application in electrochemical devices. Free sintering in air of GDC powder usually requires temperatures in the range of 1400 to 1600 °C and dwell time of several hours. Recently, it was demonstrated that sintering temperature can be significantly decreased, when sintering was performed in reducing atmosphere. Following re-oxidation at elevated temperatures was found to be a helpful measure to avoid sample failure. Sintering temperature and dwell time can be also decreased by use of Spark Plasma Sintering, also known as Field-Assisted Sintering Technique (FAST/SPS). In the present work, we combined for the first time the advantages of FAST/SPS technology and re-oxidation for sintering of GDC parts. However, GDC samples sintered by FAST/SPS were highly sensitive to fragmentation. Therefore, we investigated the factors responsible for this effect. Based on understanding of these factors, a special tool was designed enabling pressureless FAST/SPS sintering in controlled atmosphere. For proof of concept, a commercial GDC powder was sintered in this tool in reducing atmosphere (Ar-2.9%H₂), followed by re-oxidation. The fragmentation of GDC samples was avoided and the number of micro-cracks was reduced to a minimum. Prospects of GDC sintering by FAST/SPS were discussed.

This study aims to understand the effect of the electrical field on microstructure evolution during field‐assisted sintering or spark plasma sintering (FAST/SPS) of 10 mol% gadolinium‐doped ceria (GDC) with experimental and numerical methods. The novelty of this study has been the observation of enhanced grain growth in the region closer to the anode, even under FAST/SPS conditions with electrical fields less than 5 V/cm. The grain growth kinetics, including determination of activation energy and grain‐boundary mobility, were analyzed along the cross section of the samples for different temperatures and dwell periods. With an increase in distance from the anode, reduction in the activation energy for grain growth and grain‐boundary mobility was observed. These observations attributed to the attraction of oxygen ions to the anode region under an electrical field with an increase in defects along the grain boundaries. Thereby an increase in the grain‐boundary mobility and larger grains in that region were observed. A homogenous microstructure was observed in a case where the current did not flow through the sample. Furthermore, a numerical strategy has also been developed to simulate this behavior in addition to heat generation, heat transfer, and densification using Finite Element Methods (FEM) simulations. The simulation results provided an insight into the presence of a potential difference across the cross section of the samples. The simulation results were also in good agreement with the experimental observations.