Investigations of A-site substitution in sillenite-type compounds showed that only a substituent ion with a lone-electron pair can be successfully incorporated onto the A-site in place of Bi3+. This is because the stability of sillenite structural polyhedra is conditioned by the presence of a stereochemically active lone-electron pair. Accordingly, the substitutional experiments combined with an X-ray diffraction analysis, energy- and wavelength-dispersive microanalysis, and Rietveld refinement showed that Nd3+ and La3+ ions, which do not possess a lone-electron pair, cannot be incorporated into the sillenite-type structure above the detection limits of the applied analytical techniques. In contrast, the A-site substitution of Pb2+, Tl+, and Sb3+ ions, which do possess a lone-electron pair, was experimentally confirmed. Te4+ also possesses a lone-electron pair, but the substitutional experiments showed that this ion did not incorporate into the sillenite structure.
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Document Type: Research Article
Advanced Materials Department, “Jozef Stefan” Institute, 1000 Ljubljana, Slovenia
Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia
Publication date: April 1, 2004