Abstract
Perovskite-type Sr(Ti,V)O(3-δ) 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 SrTi(1-y)V(y)O(z) (y = 0.1-0.3) were prepared in air via a solid state reaction route. Thermal processing at temperatures not exceeding 1100 °C yielded composite ceramics comprising perovskite-type SrTiO(3), pyrovanadate Sr(2)V(2)O(7) and orthovanadate Sr(3)(VO(4))(2) phases, while increasing firing temperatures to 1250-1440 °C enabled the formation of SrTi(1-y)V(y)O(3) perovskites. Vanadium was found to substitute into the titanium sublattice predominantly as V(4+), 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 °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, ~10(-1) S/cm at 900 °C, whereas the transformation of oxidized vanadate phases into high-conducting SrVO(3-δ) perovskites upon reduction results in enhancement in conductivity, which reaches ~3 S/cm at 900 °C in porous composite ceramics with nominal composition SrTi(0.7)V(0.3)O(z). 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 SrVO(3) phase.