A solid-oxide fuel cell (SOFC) based upon Fe perovskites, has been designed and tested. Materials with nominal compositions Sr(0.9)K(0.1) FeO(3-delta) (SKFO) and Sr(1.6)K(0.4)FeMoO(6-delta) (SKFMO) with perovskite structure have been prepared and characterized as cathode and anode, respectively. The anode material exhibits high electrical conductivity values of 407-452 S cm(-1) at 750-820 degrees C in pure H(2). In the test cells, the electrodes were supported on a 300-mu m-thick pellet of the electrolyte La(0.8)Sr(0.2)Ga(0.83)Mg(0.17)O(3-delta) (LSGm). The single SOFC cells gave a maximum power density at 850 C of 937 mW cm(-2) with pure H(2) as a fuel. Sizeable power densities were also observed with alternative fuels: 694 and 499 mW cm(-2) with H(2) containing 5 parts per million of H(2)S and CH(4), respectively, at 800 degrees C. Moreover, only a slight degradation of about 3.6% of the power density has been obtained after 65 different cycles of fuel-cell test in H(2) at 750 degrees C and 14% at 850 degrees C in 50 cycles using H(2)-H(2)S. This remarkable behavior has been correlated to the structural features determined in a neutron powder diffraction experiment in the usual working conditions of a SOFC for a cathode (air) and an anode (low pO(2)). On the one hand, the cubic Pm-3m Sr(0.9)K(0.1) FeO(3-delta) cathode material is an oxygen deficient perovskite with oxygen contents that vary from 2.45(2) to 2.26(2) from 600 to 900 degrees C and high oxygen isotropic thermal factors (4.17(8) angstrom(2)) suggesting a high ionic mobility. On the other hand, the actual nature of the anode of composition Sr(1.6) K(0.4) FeMoO(6-delta) has been unveiled by neutron powder diffraction to consist of two main perovskite phases with the compositions SrMoO(3) and SrFe(0.6)Mo(0.4)O(2.7). The association of two perovskites oxides, SrMoO(3) with high electrical conductivity, and SrFe(0.6)Mo(0.4)O(2.7) with mixed ionic-electronic conductivity has resulted in an extraordinarily performing anode material for SOFCs. (C) 2010 Elsevier B.V. All rights reserved.