Effect of aid-sintering additives in processing of solid oxide fuel cells electrolytes by tape casting

Abstract

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 of ceramic processed by tape casting method. For this purpose, we tested three different additives: Zn, V and Fe salts and oxides. The slurry composition and thermal treatment were the same, being the green tapes sintered at 1350 °C by 6 h. 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 1350 °C shows incomplete sintering. Despite Fe and Zn act as sintering aids, we found by XRD the formation of secondary phases between LSGM and Zn. Once Fe was selected as the best additive, we treated the tapes at 1350 °C during different times to determine the optimum microstructure. 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 relation to the grain size and grain boundary density studied by Scanning Electron Microscopy and cation distribution through the electrolyte by TOF-SIMS characterization.