Synthesis and characterization of new pyrochlore solid solution Bi1.5Sb1.5–xNbxCuO7

New pyrochlore solid solutions Bi1.5Sb1.5–xNbxCuO7 have been synthesized (0 ≤ x ≤ 1.5) via the ceramic method in the air at 1000 °C. Rietveld refinement of the compounds Bi1.5Sb1.5–xNbxCuO7 for x = 0, x = 0.75 and x = 1.5 by means of X-ray powder diffraction analysis confirmed an overall A2B2O7 cubic pyrochlore structure according to (Bi3+1.5Cu2+0.5)(Sb5+1.5–xNb5+xCu2+0.5)O7 formula with 10.42009 (3) Å, 10.47193 (3) Å and 10.52679(4) Å, respectively, and Fd3¯m space group. Composition dependencies of cell parameters show a linear increase with the niobium x fraction. The magnetic susceptibility measurements achieved between 4 and 400 K indicate a paramagnetic behavior with an oxidation state “+2” for the copper ion. The electric resistivity measured using complex impedance spectroscopy evidences an increase of the electric conductivity with temperature and niobium substitution.