New pyrochlore-like phases of composition R2MnTiO7 (R = Er and Y) have been synthesized by a soft-chemistry procedure involving citrates of the different metal ions followed by thermal treatments at moderate temperatures (850 degrees C for 12 h in air). A characterization by X-ray diffraction and neutron powder diffraction (NPD) has been carried out in order to determine the crystal structure features: these phyrochlores are cubic, space group Fd-3m, defining an intrinsically frustrated three-dimensional system. The Rietveld-refinement from NPD data at room temperature evidences an antisite cation disorder (distribution of Mn between A and B positions) that is accompanied by an increment of the oxygen-vacancy concentration due to the reduction of Mn4+ at the B position to Mn2+ at the A position. Thermogravimetric analysis (TGA) was useful to evaluate the stability of these oxides in reducing conditions up to 500 degrees C. Magnetic susceptibility measurements indicate a ferromagnetic behavior, due to the random distribution of Mn4+ ions in the octahedral sublattice. At lower temperatures there is a polarization of the R+3 magnetic moments, which also participate in the magnetic structure. Aiming to evaluate these materials as possible electrodes for solid oxide fuel cells (SOFC) we determined that the thermal expansion coefficients between 100 and 900 degrees C perfectly match with those of the usual electrolytes; however, these pyrochlore oxides display a semiconductor-like behavior with poor conductivity values, e.g. 6 x 10(-3) cm(-1) at 850 degrees C for Er, which would prevent its use as MIEC (mixed ionic-electronic conductors) oxides in SOFC devices (c) 2013 Elsevier Ltd. All rights reserved.