12 research outputs found
Crystal structure of BaNaZr2F11: A phase recrystallizing from fluorozirconate glasses
International audienc
Characterization and Defect Structure of Anion-Excess Fluorite-Related Phases in LnOFâLnF3 Systems (Ln=Nd, Sm, Eu, Gd): From Isolated Defect Clustering to âVernierâ Modulated Phases
International audienc
ChemInform Abstract: High Resolution Powder Neutron Diffraction Study of the Tetragonal Anion-Excess Fluorite-Related LaF1.70O0.65 Phase.
International audienc
Short-range order and diffusion processes in the Na1-xBixF1+2x anion-excess solid solution
The Fâ diffusion processes within the anion-excess solid solution Na1âxBixF1+2x with fluorite-type structure have been studied by 19F-NMR investigation. Two types of fluoride ions, Fn and FâČ, are distinguished in the 19F-NMR spectra of rigid lattice at low temperature (T=175 K) and the distribution of fluoride ions among the two sites is determined by deconvolution of the experimental spectra. The short-range order in these materials is analogous to the clustering process observed in the K1âxBixF1+2x solid solution. It corresponds to an order between cubic entities and cubooctaedral clusters. Two diffusion mechanisms are identified on both sides of a Tr temperature. The first one at TTr to an Fâ exchange between cubic and cubooctaedral clusters
Effect of oxygen on short-range order in the Ba1-xBixF2+x solid solution
Various compositions within the range of the fluorite-type solid solution in the BaF2âBiF3âBiOl.5 system are investigated by impedance spectroscopy. This study is carried out along two lines of compositions: ÎŽ1, corresponding to the Balâ2z/3Bi2z/3F2+4z/3Oz solid solution, where z is the oxygen rate; and ÎŽ2, corresponding to the BalâxBixF2+xâ0.30O0.15 solid solution, where x is the bismuth rate. An approach to the nature of the fluorineâoxygen order is proposed which derives from the clustering process in the BalâxBixF2+x fluoride solid solution
Fluorite-like phases in the BaF 2 -BiF 3 -Bi 2 O 3 system-synthesis, conductivity and defect clustering
Abstract A fluorite-like solid solution Ba 1 Ă x Bi x O z F 2 + x Ă 2z on the basis of cubic BaF 2 was synthesised in the BaF 2 -Bi 2 O 3 -BiF 3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Ă
, c = 18.151(1) Ă
.
Fluorite-like phases in the BaF2-BiF3-Bi2O3 system-synthesis, conductivity and defect clustering
A fluorite-like solid solution Ba1 â xBixOzF2 + x â 2z on the basis of cubic BaF2 was synthesised in the BaF2-Bi2O3-BiF3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Ă
, c = 18.151(1) Ă