Effect of Aid-Sintering Additives in Processing of Solid Oxide Fuel Cells Electrolytes

SOFIA CUELLO LARREGLE; JOAQUIN RODRIGUEZ; LAURA BAQUÉ; LILIANA MOGNI

Boston

Conferencia; SSI 23 - 23rd International Conference on Solid State Ionics; 2022

MRS - Materials Research Society

Solid oxide fuel cells (SOFC) are devices that convert chemical energy into electrical energy with high efficiency and lower environmental impact than traditional technologies. They could produce fuels by H2O or CO2 electrolysis (H2, CO, CH4). They can generate high-quality heat, which allowscogeneration. Additionally, they are modular allowing a wide range of applications. Despite the abundance of raw materials, the high cost of ceramic manufacturing is currently the limiting factor for its commercialization. A way to sort it out is by reducing the number of steps and the temperature of the heat treatments required for the fabrication of the multi-component membrane electrode assembly (MEA) by co-tape and co-sintering process. The TapeCasting technique is a well-established technique to produce ceramic thin sheets. It consists in extending a ceramic powder-based slurry along a surface or carrier and controlling the thickness with a “doctor blade”. The green tape is dried and sintered to get the final layer of ceramic material. The SOFCcomponentss can be tape-casted as a single multi-layer sheet and be sintered together to simplify the manufacturing process. However, this is the biggest challenge we face because of the different microstructures (porous and dense ceramic) demand different sintering temperatures and can produce shrinkage and chemical reaction between the component materials.This research aims to investigate the processing of the LSGM (Lanthanum Gallate doped with Strontium and Magnesium) as electrolyte material and the effect of additives on reducing its sintering temperature. For this purpose, we tested three different additives: Zn, V and Fe salts and oxides. TG-DSC analysis was performed to optimize the thermal treatment. In all cases, the slurry composition and thermal treatment were the same, being the green tapes sintered at 1300°C by 8h. Both, Fe and Zn additives allow obtaining dense electrolytes, with microstructure similar to those obtained for LSGM without additives at 1500 °C. On the contrary, The LSGM treated with V and without additives at 1300 °C shows incomplete sintering. Despite Fe and Zn act assintering aids, we found by XRD the formation of secondary phases between LSGM and Zn .Once selected Fe as the best additive, we essayed different percentages of Fe(NO3)3, and Fe2O3 to determine the optimum type and amount of additive. In order to assess if the addition of additives affects the transport properties of the electrolytes, we measured its electrical properties as a function of temperature by conductivity measurements and electrochemical impedance spectroscopy (EIS). These results were analyzed in regard of the bulk and grain boundary conductivities and were correlated with grain size and grain boundary density studied by Scanning Electron Microscopy and Fe distribution through the electrolyte by TOF-SIMS characterization.