Structural and electrical properties of YXFeSbO7 (X=lanthanons or bismuth) pyrochlores

X-ray investigation of YXFeSbO7 (where X = lathanons or bismuth) compounds is carried out to find out limits of pyrochlore formation. Except YLaFeSbO7 all the compounds show pyrochlore structure. On the basis of radius ratio, stability of the compounds extends from 1.60 to 1.71 and distorted structure is observed when it is 1.74. A linear plot is observed when lattice parameters of the compounds are plotted against Shannon and Prewitt's ionic radii of X3+ ions. The electrical resistivity temperature behaviour obeys the relation delta = delta0 exp DELTA E/kT, exhibiting semiconducting nature of the compounds. The dielectric constant measurements show no variation when measured up to 773 K. (author)