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Abstract: The solid solution with formula Bi1.5Sb1.5−x Nb x MnO7 has been synthesized using the ceramic method at 1000°C. This solid solution was crystallized in the pyrohlore structure in cubic lattice with Fd-3m space group. The cell parameter increases linearly with increase in the niobium concentration. The magnetic susceptibility measurements achieved between 4 and 300K show a paramagnetic behaviour with an effective moment 5.84μβ for Bi1.5Sb1.5MnO7 compound (x =0) and 5.61μB for Bi1.5Nb1.5MnO7 compound (x =1.5) indicating “+2” oxidation state for manganese ion. The electric conductivity measured using the complex impedance spectroscopy method put in evidence an increase of the electric conductivity with the temperature, and the antimony compound is slightly more conductor than the niobium compound; results indicate electronic conductivity with semi-conducting behaviour. [Copyright &y& Elsevier]

Abstract: Synthesis and magnetic properties study of solids solutions (Bi1.524–x M x Cu0.476)[Sb1.524Cu0.476]O7+δ with M=Ca et Pb. The solid solutions with pyrochlore-like structure and general chemical formula (Bi1.524–x M x Cu0.476)[Sb1.524Cu0.476]O7+δ (M= Ca2+, Pb2+) have been synthesized by solid-state chemical reaction at high temperature. The two solutions crystallize in the cubic system, with Fd m 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 Mössbauer spectrometry of 121Sb. Magnetic susceptibility measurements showed that the effective magnetic moment of copper in these compounds decreases when bismuth is substituted for calcium. To cite this article: M. Sellami et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: Synthesis and structural determination by the Rietveld method of a new compound with pyrochlore-like structure (Bi1.524Cu0.476)(Sb1.524Cu0.476)O7+δ . A new polycristalline compound with pyrochlore-like structure and chemical formula (Bi1,524Cu0,476)(Sb1,524Cu0,476)O7+δ has been synthesized using the classical solid-state reaction method. The Rietveld structure determination shows that the cubic cell parameter is a =10.430(1) Å and the space group Fd m with eight formula units per cell. The reliability factors are R p =7.1; R wp =9.28 and R exp =5.33. The electric resistivity measured by means of the four probe method at room temperature on sintered pellets is about 105 Ω cm. The magnetic susceptibility measurements achieved between 300 and 800 K show the existence of an effective moment μeff =2.27 μB. To cite this article: M. Sellami et al., C.R. Chimie 8 (2005) . [Copyright &y& Elsevier]