Innovative processing of dense LSGM electrolytes for IT-SOFC's

This paper reports for the first time the attempted synthesis of SrO- and MgO-doped LaGaO3 (La1-xSrxGa1-yMgyO3-0.5(x+y), LSGM) perovskite by an aqueous 'regenerative' solution route. This novel technique enabled recycling of the undesired product and subsequently yielded product with much better phase purity and density than that obtained from the solid-state route. La0.8Sr0.2Ga0.85Mg0.15O2.825 (LSGM-2015) and LaGaO3 were prepared using both the regenerative sol-gel (RSG) and conventional solid-state route at 1400 degrees C. Series of La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM-2017) pellets were also prepared by the RSG method at different sintering temperature (1200-1500 degrees C) and time. The effect of conventional and microwave sintering of samples obtained from both solid-state and regenerative route was also investigated. Microwave heating was carried out using SiC as a microwave susceptor. The LSGM pellets prepared by using different synthetic methods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and pellet density was determined by pycnometry. The LSGM-2015 prepared by RSG route exhibited conductivity sigma(t) = 0.066 and 0.029 S cm(-1) at 800 and 700 degrees C, respectively, and activation energy ;of the bulk, grain-boundary, and total are E-b = 0.97 eV, Eg(b) = 1.03 eV and E-t = 1.01 eV, respectively. The sintering temperature severely affected the grain size (< 0.1-10 mu m) and also the grain-boundary resistance (3-175 k Omega). The unique aspect of this RSG technique is that the final product can be recycled which makes the process cost effective and time saving compared to the solid-state ceramic technique and this technique would allow optimization of processing parameters in a cost effective and time saving manner for obtaining well sintered LSGM as an electrolyte for IT-SOFC's. Published by Elsevier B.V.