Dense And Low Oxygen Permeability Bilayer Ceramic Interconnect For Tubular Anode-Support Solid Oxide Cells

LaCrO3-based ceramic interconnects (ICs) are currently employed in tubular solid oxide cells (SOCs), but they are facing challenges in manufacturability, durability, and cost, primarily due to Cr volatilization issues. Development of Cr-free, easy-to-manufacture, and low-cost ceramic ICs are, therefore, highly desirable for tubular SOCs. Here we report a systematic study on the chemical and physical properties of Cr-free, Y- and Nb-doped SrTiO3-delta (Sr1-xYxTi1-yNbyO3, SYTN, 0 <= x, y <= 0.1) as a ceramic IC. While similar systems have been studied in the literature, our study has focused on optimizing SYTN compositions, examining chemical compatibility between SYTN and anode substrate, fabricating bilayer structure, cosintering it with anode substrate, and testing its performance under practical oxidizing-reducing dual atmospheres. The results show that SYTN(Y0.08Nb0.02) is the best composition as an IC since it exhibits high electrical conductivity and can be cosintered with Ni-YSZ anode substrate into a dense microstructure without any chemical reactions. A first-principles theoretical study reveals that Y-and Nb-doping transforms semiconducting SrTiO3 into itinerant large-polarons metal, confirming the high electrical conductivity. A bilayer IC consisting of La0.8Sr0.2MnO3-delta (LSM) top-layer and SYTN(Y0.08Nb0.02) underlayer cosintered on the anode substrate is also demonstrated with dense microstructure, low area specific resistance and negligible oxygen permeability. Overall, the cosintered bilayer ceramic IC is a promising candidate for next-generation durable, and low-cost tubular SOCs.