Synthesis and magnetic properties study of solids solutions (Bi_(1.524-x)M_xCu_(0.476))[Sb_(1.524)Cu_(0.476)]O_(7+delta) with M = Ca et Pb.

摘要

The solid solutions with pyrochlore-like structure and general chemical formula (Bi_(1.524-x)M_xCu_(0.476))[Sb_(1.524)Cu_(0.476)]O_(7+delta) (M = Ca~(2+),Pb~(2+)) have been synthesized by solid-state chemical reaction at high temperature.The two solutions crystallize in the cubic system,with Fd3m space group.Domains of homogeneity are 0 <= x <= 0.30 and 0 <= x <= 0.26 for calcium and lead,respectively.A regular decreasing of the cell parameter has been observed in the calcium solid solution.The state oxidation +5 of antimony has been put in evidence by the Mossbauer spectrometry of ~(121)Sb.Magnetic susceptibility measurements showed that the effective magnetic moment of copper in these compounds decreases when bismuth is substituted for calcium.