Low-temperature constrained sintering of YSZ electrolyte with Bi2O3 sintering sacrificial layer for anode-supported solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have strong potential for next-generation energy conversion systems. However, their high processing temperature due to multi-layer ceramic components has been a major challenge for commercialization. In particular, the constrained sintering effect due to the rigid substrate in the fabrication process is a main reason to increase the sintering temperature of ceramic electrolyte. Herein, we develop a bi-layer sintering method composed of a Bi2O3 sintering sacrificial layer and YSZ main electrolyte layer to effectively lower the sintering temperature of the YSZ electrolyte even under the constrained sintering conditions. The Bi2O3 sintering functional layer applied on the YSZ electrolyte is designed to facilitate the densification of YSZ electrolyte at the significantly lowered sintering temperature and is removed after the sintering process to prevent the detrimental effects of residual sintering aids. Subsequent sublimation of Bi2O3 was confirmed after the sintering process and a dense YSZ monolayer was formed as a result of the sintering functional layer-assisted sintering process. The sintering behavior of the Bi2O3/YSZ bi-layer system was systematically analyzed, and material properties including the microstructure, crystallinity, and ionic conductivity were analyzed. The developed bi-layer sintered YSZ electrolyte was employed to fabricate anode-supported SOFCs, and a cell performance comparable to a conventional high temperature sintered (1400 C) YSZ electrolyte was successfully demonstrated with significantly reduced sintering temperature (< 1200 C).