Constrained flash sintering of gadolinium‐doped ceria thin layers

Abstract

Flash sintering is a novel technology, which enables densification of ceramics in seconds to minutes at moderate furnace temperatures. To date, it has mostly been demonstrated on samples with simple geometries like dog bones, bars, or cylinders, which are quite far from real applications. In the present work, we extend flash sintering to gadolinium-doped ceria (GDC) thin ceramic layers (∼15 × 8 × 0.008 mm³) screen printed onto rigid alumina substrates. Building on our previous work with GDC dog bones, we selected the same material due to its relevance for solid oxide cell applications. All experiments were performed isothermally under voltage-to-current control mode. Flash sintering was triggered under relatively high electric fields (> 500 V cm⁻¹), current densities (> 600 mA mm⁻²), and furnace temperatures (> 1100°C), as indicated by the characteristic abrupt increase in the specimen's conductivity and bright light emission. However, significant effects of the electric current were observed at a furnace temperature of 1200°C, with current densities above 800 mA mm⁻², and a dwell time of 180 min, leading to relative densities above 90%, compared to only 75% for conventional sintering under the same temperature and time. The harsher conditions needed to flash sinter these specimens are explained by the very high aspect ratio (surface area-to-volume) compared to other usual geometries in flash sintering experiments. In addition, the heat dissipation in the special experimental setup plays an important role in terms of energy balance.