Relations between the structure, ionic conductivity and dielectric properties of fluoride systems of different structures containing rare earth elements were presented. Superionic conductivities, by fluoride ions, of ...Relations between the structure, ionic conductivity and dielectric properties of fluoride systems of different structures containing rare earth elements were presented. Superionic conductivities, by fluoride ions, of fluorite-structured （MF2-REF3, M=Ba, Pb, RE=La-Lu, Sc, Y）, orthorhombic （REF3, RE=Tb-Er, Y）, tysonite-structured （REF3-MF2, RE=La-Nd, M=Sr）, monoclinic （BaRE2Fs, RE=Ho-Yb, Y） fluoride single crystals and eutectic composites （LiF-REF3, RE=La-Gd, Y） were compared. Anisotropy of electrical properties of crystals with a lower symmetry was explained by modeling optimum ionic paths. For explanation of concentration dependences of fast ionic conductivity, models of aggregation of defects into clusters were proposed. In fluorite-structured crystals, the highest ionic conductivity was found for PbF2：7 mol% ScF3 （at 500 K, σ500=0.13 S/cm）. In tysonite-structured crystals, the highest ionic conductivity was found for LaF3：3 mol% SrF2 （σ500=2.4×10^-2 S/cm）. Different types of coordination polyhedrons and their different linking in orthorhombic and tysonite structure explained large differences between conductivities in both structures. Eutectic systems, prepared as directionally solidified composites, enabled to study some orthorhombic fluoride phases （GdF3, SmF3）, which cannot be prepared as single crystals. An influence of the orthorhombic-tysonite phase transition on the ionic conductivity was shown.展开更多
Fluoride glasses containing rare earths exhibit interesting spectroscopic properties.They have wide transmission range from 0.25μm in the UV to 7μm in the IR,allowing observation,in a vitreous material,of absorption...Fluoride glasses containing rare earths exhibit interesting spectroscopic properties.They have wide transmission range from 0.25μm in the UV to 7μm in the IR,allowing observation,in a vitreous material,of absorption and emission bands in a large optical range.The absorption spectra of fluoride glasses with rare earth substitutions are found to vary with the rare earth ions used.The T_g~'s for these glasses average out at 311℃.Optical properties,such as refractive indices are not obviously influenced by rare earth substitutions.展开更多
基金the Scientific Grant Agency VEGA, Slovak Republic (1/2100/05 and 1/0173/08)
文摘Relations between the structure, ionic conductivity and dielectric properties of fluoride systems of different structures containing rare earth elements were presented. Superionic conductivities, by fluoride ions, of fluorite-structured （MF2-REF3, M=Ba, Pb, RE=La-Lu, Sc, Y）, orthorhombic （REF3, RE=Tb-Er, Y）, tysonite-structured （REF3-MF2, RE=La-Nd, M=Sr）, monoclinic （BaRE2Fs, RE=Ho-Yb, Y） fluoride single crystals and eutectic composites （LiF-REF3, RE=La-Gd, Y） were compared. Anisotropy of electrical properties of crystals with a lower symmetry was explained by modeling optimum ionic paths. For explanation of concentration dependences of fast ionic conductivity, models of aggregation of defects into clusters were proposed. In fluorite-structured crystals, the highest ionic conductivity was found for PbF2：7 mol% ScF3 （at 500 K, σ500=0.13 S/cm）. In tysonite-structured crystals, the highest ionic conductivity was found for LaF3：3 mol% SrF2 （σ500=2.4×10^-2 S/cm）. Different types of coordination polyhedrons and their different linking in orthorhombic and tysonite structure explained large differences between conductivities in both structures. Eutectic systems, prepared as directionally solidified composites, enabled to study some orthorhombic fluoride phases （GdF3, SmF3）, which cannot be prepared as single crystals. An influence of the orthorhombic-tysonite phase transition on the ionic conductivity was shown.
文摘Fluoride glasses containing rare earths exhibit interesting spectroscopic properties.They have wide transmission range from 0.25μm in the UV to 7μm in the IR,allowing observation,in a vitreous material,of absorption and emission bands in a large optical range.The absorption spectra of fluoride glasses with rare earth substitutions are found to vary with the rare earth ions used.The T_g~'s for these glasses average out at 311℃.Optical properties,such as refractive indices are not obviously influenced by rare earth substitutions.
