Investigation of the alpha-BiOyF3-2y-Based Tysonite-type Solid Solutions by X-ray Diffraction and Impedance Spectroscopyстатья
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Дата последнего поиска статьи во внешних источниках: 20 сентября 2013 г.
Аннотация:Tysonite solid solutions Bi1-xMx(O,F)(3-d) (M = Na, Sr, or Nd) based on alpha-BiOyF(3-2y) were prepared by solid-state synthesis at 873 K with subsequent quenching to ice-cold water. Aliovalent substitutions in both the cation and anion sublattices (Mn+--> Bi3+ and O2---> F-) made it possible to vary the anion-vacancy density. The solid solutions were characterized by X-ray diffraction and impedance spectroscopy. The homogeneity regions for the tysonite solid solution were determined; triangulation schemes at 873 K were suggested for the systems BiF3-BiOF-NaBiF4 and BiF3-BiOF-SrF2, and a scheme of the subsolidus phase diagram for the system BiO0.1F2.8-NdF3 was suggested. In the system BiO0.1F2.8-NdF3, the transition temperature from the low-symmetry tysonite phase (phase II, space group P (3) over bar c1, Z = 6) to the high-symmetry one (phase I, space group P6(3)/mmc, Z = 2) decreases with increasing anion-vacancy density. Conductivity measurements were performed in the temperature range 300-523 K and the frequency range from 5 to 1 x 106 Hz. The conductivity of samples in the system BiO0.1F2.8-NdF3 increases with increasing bismuth-ion and anion-vacancy concentrations.