We have studied the new compounds with fluorite-like (Ho2RNbO7 (R = Lu, Sc)) and pyrochlore-like (Sm2ScTaO7) structure as potential oxide ion conductors. The phase formation process (from 1200 to 1600 degrees C) and physical properties (electrical, thermo mechanical, and magnetic) for these compounds were investigated. Among the niobate materials the highest bulk conductivity is offered by the fluoritelike Ho2ScNbO7 synthesized at 1600 degrees C: 3.8 x 10(-5) S/cm at 750 degrees C, whereas in Sm system the highest bulk conductivity, 7.3 x 10(-6) Slcm at 750 degrees C, is offered by the pyrochlbre Sm2ScTaO7 synthesized at 1400 degrees C. In Sm2ScTaO7 pyrochlore we have observed the first-order phase transformation at similar to 650-700 degrees C is related to rearrangement process in the oxygen sublattice of the pyrochlore structure containing B-site cations in different valence state and actually is absent in the defect fluorites. The two holmium niobates show Curie-Weiss paramagnetic behavior, with the prevalence of antiferromagnetic coupling. The magnetic susceptibility of Sm2ScTaO7 is a weak function of temperature, corresponding to Van Vleck paramagnetism. (C) 2013 Elsevier Ltd. All rights reserved.