(Digital Presentation) GDC/YSZ Bilayer Electrolyte Fabrication by In-situ Hydrothermal Growth

Abstract

GDC (gadolinia-doped ceria) can be used as barrier layer between the high-performance LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode and YSZ (8% mol yttria stabilized zirconia) electrolyte, to prevent chemical incompatibility and elements diffusion. However, the GDC layer is difficult to achieve as high density as the YSZ electrolyte, especially under low sintering temperatures. While, increase sintering temperature over ~1200 ℃ could induce the formation of (Ce,Zr)O2 solid solution.In this work, we report a highly dense bilayer GDC/YSZ electrolyte prepared at low sintering temperature. Specifically, the as-sintered anode supported SOFC half-cell with already-dense YSZ electrolyte was immersed in solution of Gd(NO3)3·6H2O and Ce(NO3)3·6H2O, followed by a hydrothermal treatment at 180 ℃ (accounts for steam pressure of ~1 MPa) for 36 h. This yielded a dense GDC layer growth on YSZ electrolyte with thickness of ~200 nm. Then, the cells were sintered at 1100, 1150 and 1200 ℃, respectively. Afterwards, the hydrothermal treatment was repeated once, to grow an additional GDC layer. This post-grown GDC was then co-sintered with the screen printed LSCF cathode at 1075 ℃.Results show that, the GDC/YSZ bilayer electrolyte is successfully fabricated under low sintering temperature below 1200 ℃, with overall GDC layer as thick as ~540 nm and ultra-high density as the YSZ electrolyte. The single cell with 1200 ℃ sintered GDC, named as GDC-1200, shows the best output performance, i.e. maximum power density of ~0.96 W/cm2 at 780 ℃. Moreover, the cell runs stably at 720 ℃ for 300 hours, showing decent durability.Fig. 1 (a) j-V-P curves of bilayer electrolyte SOFCs with varied GDC sintering temperature; (b) operation voltage versus time for GDC-1200 cell under constant current mode; (c) SEM images and (d) EDS mapping of single cell (GDC-1200) fracture Figure 1