THE SYNTHESIS AND STRUCTURAL AND PHYSICAL CHARACTERIZATION OF A NEW FAMILY OF RARE-EARTH-METAL CHALCOANTIMONATES(III) - K-2(RE)(2-X)SB4+XSB4SE12, RE=LA, CE, PR AND GD

A family of rare-earth metal selenoantimonates(III) has been prepared by the reaction of the elements in alkali metal polyselenide fluxes or by the metathesis of rare-earth chlorides and alkali metal chalcoanti monates(III). The products are black, fine needles of K-2(RE)(2-x)Sb4xSe12 where RE=La, Ce, Pr, and Gd and x similar to 0.33. The compounds were analyzed by single crystal and powder X-ray diffraction, and the praseodymium compound by diffuse reflectance spectroscopy, and magnet ic susceptibility. The structure, optical spectrum, and susceptibility data of the praseodymium compound are reported.