Structural, infrared, and magnetic characterization of the solid solution series Sr{sub 2{minus}x}Pb{sub x}(VO)(VO{sub 4}){sub 2}; Evidence of the Pb{sup 2+} 6s{sup 2} lone pair stereochemical effect
- Univ. des Sciences et Technologies de Lille, Villeneuve d`Ascq (France). Lab. de Cristallochimie et Physicochimie du Solide
- Univ. of Texas, Austin, TX (United States)
The solid solution Sr{sub 2{minus}x}Pb{sub x}V{sub 3}O{sub 9}, 0 {le} x {le} 2, was prepared by solid state reactions and characterized by X-ray diffraction, IR spectroscopy, and magnetic susceptibility measurements. Single crystals of the pure strontium phase and mixed Sr/Pb compounds were prepared by high temperature treatment of the respective powder compositions. Pb{sub 2}V{sub 3}O{sub 9} crystals could only be obtained by the electrochemical reduction of molten PbV{sub 2}O{sub 6}. These crystals were always twinned. The previously reported crystal structure of Sr{sub 2}V{sub 3}O{sub 9} was confirmed. It was refined to R = 0.050, R{sub 2} = 0.057, in space group C2/c, a = 7.555(1) {angstrom}, b = 16.275(2) {angstrom}, c = 6.948(1) {angstrom}, {beta} = 119.78(1){degree}. The single crystal structural studies of the Sr{sub 1.02}Pb{sub 0.98}V{sub 3}O{sub 9} and Sr{sub 0.67}Pb{sub 1.33}V{sub 3}O{sub 9} members of the series show that the introduction of lead gives rise to a progressively complicated splitting of Sr{sup 2+}/Pb{sup 2+} and the tetrahedral vanadium ion crystallographic sites. As a consequence the vanadium framework distorts and beyond the Sr{sub 0.5}Pb{sub 1.5}V{sub 3}O{sub 9} composition the crystal symmetry becomes triclinic. This distortion is ascribed to the stereochemical effect of the 6s{sup 2} lone pair of Pb{sup 2+}. The crystallographic parameters of Pb{sub 2}V{sub 3}O{sub 9} are a = 7.598(1) {angstrom}, b = 16.393(3) {angstrom}, c = 6.972(2) {angstrom}, {alpha} = 91.38(1){degree}, {beta} = 119.35(1){degree}, {gamma} 90.47(1){degree}. Pb{sub 2}V{sub 3}O{sub 9} exhibits a more complex IR spectrum than the monoclinic phases. Despite the similarity between the triclinic and monoclinic phases the magnetic susceptibilities indicate differences in the coupling between 4{sup 4+} ions at low temperatures.
- OSTI ID:
- 305384
- Journal Information:
- Journal of Solid State Chemistry, Vol. 140, Issue 2; Other Information: PBD: 1 Nov 1998
- Country of Publication:
- United States
- Language:
- English
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