SrTiO3-SrVO3 Ceramics for Solid Oxide Fuel Cell Anodes: A Route from Oxidized Precursors

Perovskite-type Sr(Ti,V)O3-delta ceramics are promising anode materials for natural gas-and biogas-fueled solid oxide fuel cells, but the instability of these phases under oxidizing conditions complicates their practical application. The present work explores approaches to the fabrication of strontium titanate-vanadate electrodes from oxidized precursors. Porous ceramics with the nominal composition SrTi1-yVyOz (y = 0.1-0.3) were prepared in air via a solid state reaction route. Thermal processing at temperatures not exceeding 1100 degrees C yielded composite ceramics comprising perovskitetype SrTiO3, pyrovanadate Sr2V2O7 and orthovanadate Sr-3(VO4)(2) phases, while increasing firing temperatures to 1250-1440 degrees C enabled the formation of SrTi1-yVyO3 perovskites. Vanadium was found to substitute into the titanium sublattice predominantly as V4+, even under oxidizing conditions at elevated temperatures. Both perovskite and composite oxidized ceramics exhibit moderate thermal expansion coefficients in air, 11.1-12.1 ppm/K at 30-1000 degrees C, and insignificant dimensional changes induced by reduction in a 10%H-2-N-2 atmosphere. The electrical conductivity of reduced perovskite samples remains comparatively low, similar to 10-1 S/cm at 900 degrees C, whereas the transformation of oxidized vanadate phases into high-conducting SrVO3-delta perovskites upon reduction results in enhancement in conductivity, which reaches similar to 3 S/cm at 900 degrees C in porous composite ceramics with nominal composition SrTi0.7V0.3Oz. The electrical performance of the composite is expected to be further improved by optimization of the processing route and microstructure to facilitate the reduction of the oxidized precursor and attain better percolation of the SrVO3 phase.