High-temperature degradation of tetragonal zirconia in solid oxide fuel and electrolysis cells: A critical challenge for long-term durability and a solution

Solid oxide fuel and electrolysis cells (SOCs) are promising devices for efficiently generating electricity and hydrogen/syngas, respectively. The preferred cell configuration by many industrial developers consists of a Ni(O)-3YSZ fuel electrode support or a 3YSZ electrolyte support, which allows the manufacturing of large-area cells. 3YSZ, like many other transformable tetragonal zirconia ceramics, is well-known to be susceptible to hydrothermal degradation at temperatures below 400 °C (LTD) but is widely believed to withstand this degradation at higher temperatures. In this work, we present our recent finding that 3YSZ is, in fact, susceptible to high-temperature degradation (HTD) after operation over 8,500-10,000 h. The degradation leads to substantial embrittlement of the cells. In addition, we report on the excellent resistance to LTD and HTD of a newly developed fine-grained Ni-3YSZ support. This study highlights the importance of using HTD-resistant tetragonal zirconia ceramics in developing the next generation of strong and durable ceramic-supported SOCs.