Ionic Conductivity of the new Fluoride-Ion Conductor Casn2F6

2002 ◽  
Vol 756 ◽  
Author(s):  
Michael F. Bell ◽  
Georges DéNés ◽  
Zhimeng Zhu
Keyword(s):  
Solid Solution ◽  
Complex Impedance ◽  
Crystalline Material ◽  
Mixed Conductor ◽  
Impedance Method ◽  
Fluoride Ion ◽  
Ion Conductor ◽  
Covalently Bonded ◽  
Fluorite Type ◽  
First Time

ABSTRACTMetastable CaSn2F6 has been prepared for the first time and characterized. It is a well crystalline material that leaches SnF2 in water to give the microcrystalline fluorite-type Ca1-xSnxF2 solid solution. In both materials, tin(II) is covalently bonded to fluorine, and thus carries a stereoactive non-bonding electronic pair. The electrical conductivity of CaSn2F6 was measured by the complex impedance method. The CaSn2F6 material was found to be a mixed conductor (τi = 0.50), with a F- conductivity a little below that of α-SnF2. On heating to 250°C, it decomposes irreversibly to give SnF2 and probably amorphous CaF2 (undetected).

Electrical Characterization of the Structure and Other Phenomena in Superionic PbSnF4

1995 ◽  
Vol 411 ◽  
Author(s):  
Galina Milova ◽  
Georges Denes ◽  
M. Cecilia Madamba ◽  
M. Perfiliev
Keyword(s):  
Ion Mobility ◽  
Complex Impedance ◽  
Electrical Characterization ◽  
Fold Increase ◽  
Fluoride Ion ◽  
Fluoride Ions ◽  
Covalently Bonded ◽  
Frenkel Defects ◽  
Fluorite Type

ABSTRACTThe structure of PbSnF4 is derived from that of fluorite-type β-PbF2 The replacement of half the lead by tin results in a thousand-fold increase of the fluoride ion mobility, even though tin-fluorine bonds are strongly covalent. This is due to an increase of fluoride ion disorder on some sites. The structure of α-PbSnF4 can be interpreted as resulting from the insertion of two layers of [SnF]+ cations between each pair of layers of PbF8 cubes. This has profound bearings on the texture and properties of this material, since the tin(II) stereoactive lone pairs create very effective cleavage planes. In addition, the fluorine covalently bonded to tin occupy all vacant sites used to create Frenkel defects. However, superionicity is observed by complex impedance measurements. Transport number measurements show that fluoride ions are the charge carriers.

scholarly journals Собственная фтор-ионная проводимость кристаллических матриц фторидных супериоников: BaF-=SUB=-2-=/SUB=- (тип флюорита) и LaF-=SUB=-3-=/SUB=- (тип тисонита)

2019 ◽  
Vol 61 (1) ◽  
pp. 53
Author(s):  
Н.И. Сорокин ◽  
Б.П. Соболев
Keyword(s):  
Structural Type ◽  
Inert Atmosphere ◽  
Impedance Method ◽  
Energy Characteristics ◽  
Thermally Activated ◽  
Vacuum Technology ◽  
Structural Types ◽  
Fluorite Type ◽  
And Migration ◽  
First Time

AbstractThe intrinsic fluorine-ion conductivity σ_lat of BaF_2 (CaF_2 fluorite type) and LaF_3 (tysonite type) crystals is studied by the impedance spectroscopy method. These compounds represent two major structural types taken as the basis to form the best nonstoichiometric fluorine-conducting solid electrolytes. The conductivity σ_lat caused by thermally activated defects is manifested in the field of high temperatures, where conductometric measurements are complicated by pyrohydrolysis. The experiments carried out in inert atmosphere with application of the impedance method have for the first time produced the reliable values of σ_lat of fluoride crystals in conditions of suppression of pyrohydrolysis (BaF_2) or partial pyrohydrolysis (LaF_3). Values of the σ_lat at 773 K for BaF_2 and LaF_3 crystals grown from melt by the Bridgman method using the vacuum technology are 2.2 × 10^–5 and 8.5 × 10^–3 S/cm differing by a factor of ~400. The tysonite structural type has been proved feasible for making high-conductivity solid fluoride electrolytes based on the analysis of energy characteristics of formation and migration of anionic defects.

Use of Mössbauer Spectroscopy for the Characterization of Order/Disorder Phenomena in Tin(II) Containing Ionic Conductors and for Making Predictions Regarding Possible Electron Contribution to the Conduction

1998 ◽  
Vol 548 ◽  
Author(s):  
Georges Dénès ◽  
M. Cecilia Madamba ◽  
Abdualhafeed Muntasar ◽  
Alena Peroutka ◽  
Korzior Tam ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
Fluorite Structure ◽  
Mixed Conductor ◽  
Fluoride Ion ◽  
Ionic Conductors ◽  
Mößbauer Spectroscopy ◽  
Electron Contribution ◽  
Fluorite Type

ABSTRACTMössbauer spectroscopy has been seldom used for the characterization of ionic conductors. However, since the introduction of divalent tin in MF2 fluorites (M = Sr, Pb and Ba) to form MSnF4, PbSn4F10 or the Pb1−xSnxF2 solid solution, all of which have structures closely related to the fluorite type, results in an enhancement of the fluoride ion conductivity by up to three orders of magnitude, and since 119 Sn is the second best Mössbauer nuclide, it seems that the Mössbauer technique could provide useful information about how tin(II) modifies the fluorite structure and leads to such a tremendous enhancement of the fluoride ion mobility. The MF2/SnF2 systems contain some number of materials that show order/disorder phenomena (between M and Sn, and also between different fluorine atoms) which make it difficult to understand them from diffraction data only. Mössbauer spectroscopy has been invaluable in helping understand the local structure at tin. By probing the valence electronic structure of tin, we can also make predictions on the possible long range mobility of the tin(II) non-bonded electron pair, which would make the material an electronic conductor or a mixed conductor.

High fluoride-ion conductivity and fluoride-ion conductor−insulator transition in fluorinated hexagonal boron nitride

2021 ◽  
Vol 21 ◽  
pp. 100523
Author(s):  
Tsuyoshi Takami ◽  
Takashi Saito ◽  
Takashi Kamiyama ◽  
Katsumi Kawahara ◽  
Toshiharu Fukunaga ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Insulator Transition ◽  
Ion Conductivity ◽  
Fluoride Ion ◽  
Ion Conductor ◽  
High Fluoride

Mechanosynthesis, Radiation-Thermal Modification and Characterization of Nanostructured Scandia Stabilized Zirconia Ceramics

2008 ◽  
Vol 1122 ◽  
Author(s):  
Vladimir V. Zyryanov ◽  
Nikolay F. Uvarov ◽  
Artem S. Ulihin ◽  
Vladislav A. Sadykov
Keyword(s):  
Solid Electrolytes ◽  
Room Temperature ◽  
Complex Impedance ◽  
Impedance Method ◽  
Sintering Aids ◽  
Zirconia Ceramics ◽  
Operation Temperature ◽  
Cubic Structure ◽  
Xrd Patterns

AbstractSSZ-based ceramics were obtained by sintering of nanopowders derived at room temperature by mechanochemical synthesis from refined technical grade ZrO2 nano-precursors. RT-treatment by 2.5 MeV electrons up to 1563 K was used for the modification of ceramics. Powders and ceramics were characterized by XRD, Raman, SEM and EDS, TEM, SIMS techniques. The phase composition of Zr0.89Sc0.1Ce0.01O1.95 ceramics was very close to cubic structure but better fitting of XRD patterns was obtained for rhombohedral lattice. Conductivity of solid electrolytes for IT SOFC was studied by complex impedance method. To stabilize cubic structure and increase conductivity at operation temperature of To ∼ 1000 K, the composition of SSZ solid electrolyte was optimized by addition of yttria and sintering aids. The interaction of admixtures with minor dopants leading to intergrain phase was revealed. During fast sintering, ceramics keep a memory about inhomogeneous disordered solid solutions in a form of nanostructuring. Conductivity data indicate nanostructuring of ceramics too: activation energies of bulk and grain boundary conductivities are close (Eb ∼ 0.9 eV, Egb ∼ 1.05 eV). Annealing of ceramics at high temperatures increases conductivity at To and promotes grain growth.

The Defect Fluorite Phase in the ZrO2-PrO1.5 System and Its Relationship to the Structure of Pyrochlore

1992 ◽  
Vol 45 (9) ◽  
pp. 1375 ◽  
Author(s):  
RL Withers ◽  
JG Thompson ◽  
PJ Barlow ◽  
JC Barry
Keyword(s):  
Solid Solution ◽  
Point Defects ◽  
Phase Field ◽  
Fluorite Phase ◽  
X Ray ◽  
Average Structure ◽  
Transmission Electron ◽  
Solution Field ◽  
Close Relationship ◽  
Fluorite Type

A detailed transmission electron microscope and X-ray powder diffraction study has been made of the so-called 'defect fluorite' phase field in the ZrO2-PrO1.5 system and of its close relationship to the pyrochlore solid solution field in the same system. Even for the lowest possible PrO1.5 content within the 'defect fluorite' phase field, it is clear that the sharp Bragg reflections characteristic of the underlying fluorite average structure are accompanied by some of the 'satellite reflections' characteristic of the pyrochlore solid solution field. As the PrO1.5 content increases, these satellite reflections increase systematically in intensity as well as sharpening very considerably. It is shown that this 'defect fluorite' phase field cannot be adequately described either in terms of random point defects within an average fluorite-type matrix or in terms of a diphasic texture of pyrochlore domains embedded coherently into a fluorite matrix, but must be regarded as enuinely intermediate between these two end-member structures and of commensurately modulated fluorite type. A group theoretical approach is used to propose a model for the structural deviation from the underlying fluorite average structure.

Production and Study of Ca/Sn(II) Metastable Fluoride Ion Conductors

1997 ◽  
Vol 481 ◽  
Author(s):  
Michael F. Bell ◽  
Georges Dénès ◽  
Zhimeng Zhu
Keyword(s):  
Solid Solution ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Calcium Nitrate ◽  
Fluoride Ion ◽  
Conductivity Measurements ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Density Measurements ◽  
Ion Conductors

ABSTRACTPrecipitation reactions from aqueous solutions of calcium nitrate and tin(II) fluoride result in the formation of two metastable phases, depending on the reaction conditions. Crystalline CaSn2F6 and the microcrystalline Ca1-xSnxF2 solid solution are obtained, the latter crystallizing in the cubic fluorite (CaF2) type with total Ca/Sn disorder. Both phases are fluoride ion conductors. Electrical conductivity measurements versus temperature and bulk density measurements show that both phases are far from thermodynamic equilibrium at ambient conditions, and thus are metastable. Both decompose to a mixture of SnF2 and CaF2 at high temperature. In addition, CaSn2F6 is chemically unstable in an aqueous medium, in which it looses SnF2 to give the microcrystalline Ca1-xSnxF2 solid solution.

Synthesis and characterization of mixed fluorides with PbF2 and ScF3

2005 ◽  
Vol 20 (3) ◽  
pp. 254-258 ◽  
Author(s):  
S. N. Achary ◽  
A. K. Tyagi
Keyword(s):  
Solid Solution ◽  
Phase Equilibria ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Solubility Limit ◽  
Synthesis And Characterization ◽  
Temperature Phase ◽  
Fluorite Type ◽  
Low Temperature Phase

A series of mixed fluoride compositions with PbF2 and ScF3 were prepared by heating the intimate mixtures of component fluorides at 600 °C for 10 h followed by slowly cooling to room temperature. The products obtained were analyzed by powder XRD to reveal the phases present in them and hence the low-temperature phase equilibria in the PbF2-ScF3 system. The phase equilibria show the fluorite-type solid solution up to the composition of about 15 mol% of ScF3 in the PbF2 lattice. The unit cell volume decreases with increasing ScF3 contents in the fluorite-type solid solutions. Beyond the solubility limit, the biphasic mixture of the cubic fluorite-type solid solution and leftover ScF3 is found to exist.

151Eu Mössbauer spectroscopic and XRD study on some fluorite-type solid solution systems, EuyM1−yO2−y/2 (M=Zr, Hf, Ce)

2002 ◽  
pp. 305-308 ◽  
Author(s):  
N. M. Masaki ◽  
H. Otobe ◽  
A. Nakamura ◽  
N. R. D. Guillermo ◽  
Y. Izumiyama ◽  
...  
Keyword(s):  
Solid Solution ◽  
Xrd Study ◽  
Fluorite Type
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