New Synthetic Route for Reaching Higher Phase Stabilization in LAMOX-Based Electrolyte for Solid Oxide Fuel Cells

Abstract

S-substituted La2Mo2O9 were synthesized by a solid-state procedure employing ammonium sulfate (NH4)2SO4 as a sulfur source. The synthesized powders were examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared, and Raman spectroscopies. The results divulged that the stabilization of the β-La2Mo2O9 polymorph occurred in the interval of sulfur composition 0.1≤y≤0.6. This substitution generates a linear dwindling of the unit cell volume. The decomposition of all substituted samples started above 900 °C with a total weight loss linearly dependent on the sulfur content. Electrical studies confirmed that substituting S6+ for Mo6+ suppresses the phase transition of La2Mo2O9 and stabilizes the cubic polymorph down to ambient temperature. It was also remarkable that this substitution caused a decrease in the conductivity, and unfortunately, none of the tested compositions allowed exceeding the conductivity of La2Mo2O9. Infrared and Raman spectra confirmed the presence of the characteristic peaks of sulfates and molybdates groups.