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Abstract: This review article presents a brief overview of synthesis and application aspects of fast fluoride ion conducting materials in the field of Solid State Ionics. Possible synthesis methodologies known in the literature for the preparation of various fluoride materials have been outlined. Further, their transport characteristics with respect to their crystal structure have been discussed. Various approaches influencing their ionic conductivity value in the light of synthesis methodology, composition, dopant concentration, crystallite size, microstructure etc. have been reviewed. At the end, possible technological applications of fast fluoride ion conducting materials in different solid state ionic devices have been presented. [Copyright &y& Elsevier]

Abstract: The high performance fluoride ion conductor BaSnF4 has been prepared by a simple precipitation in addition to both solid state reaction and mechanochemical synthesis techniques. XRD results indicate that the material BaSnF4 obtained by all the methods crystallizes with the same tetragonal structure (P4/nmm). The crystallite size and morphology of the BaSnF4 particles determined by XRD and FE-SEM show a variation with respect to different methods of preparation. The transport properties of BaSnF4 have been investigated by impedance spectroscopy and the results show that the conductivity values are closely related to the crystallite size and micro-strain. The transport number measurement and NMR studies further confirm that the increase in conductivity is due to fluoride ions. The scaling result of complex impedance plots shows that the dynamical process occurring at various frequencies are independent of temperature. [Copyright &y& Elsevier]

Abstract: The conduction characteristics of SnF2 from room temperature (300K) to 463K have been investigated by using impedance spectroscopy. The temperature dependent conductivity plot shows a break in conductivity around 443K corresponding to the α→γ phase transition temperature. The electrical properties of SnF2 are also investigated by extracting dielectric and modulus data from impedance values. The frequency dependent plots of M″ and Z″ show that the conductivity relaxation is non-Debye in nature. The activation energy responsible for relaxation has been calculated from the modulus spectra and is found to be almost the same as that from the temperature dependent dc conductivity data. The real part of conductivity and permittivity in addition to the modulus spectra of the present system show scaling behavior, which means σ′(ω), ɛ′(ω) and M′(ω) isotherms successfully collapse to a single master curve indicating that the relaxation mechanism is temperature independent. Different scaling approaches have been applied to arrive at a correlation between the scaling parameters. [Copyright &y& Elsevier]

Abstract: Sodium pentafluorodistannite has been synthesized through high-energy ball milling as well as by solid-state reaction method and characterized through XRD and DSC techniques. The electrical conductivity and modulus characteristics of the system are investigated in the temperature range from 373K to 473K by means of impedance spectroscopy. The conductivity of the ball-milled sample is about one order of magnitude higher compared to the sample prepared by solid-state reaction method. The frequency dependent conductivity of the present system shows the power law feature. The real part of dielectric permittivity shows a huge value at lower frequencies due to the presence of space charge polarization. The activation energy responsible for relaxation calculated from the modulus spectra is found to be almost the same as the value obtained from temperature variation of dc conductivity. The conductivity and modulus spectra of the present system show scaling behavior, which means that σ*(ω) and M″(ω) isotherms successfully collapse to a single master curve indicating temperature independent relaxation behavior. [Copyright &y& Elsevier]

Abstract: SnF2 of various crystallite sizes have been obtained by mechanical milling. Further, the crystallite size dependent conduction characteristics of SnF2 have been investigated by X-Ray Diffraction, High Resolution Scanning Electron Microscopy and Impedance Spectroscopy techniques. The crystallite size and microstrain developed during the milling process have been calculated by using Scherrer''s semi-empirical formula. Further, an attempt is made to correlate the conductivity results of mechanically milled samples with the crystallite size and microstrain. In all cases, the temperature dependent conductivity plot obeys the Arrhenius behavior. The enhancement in conductivity of SnF2 is found to be of two orders of magnitude after simply milling for 10h. [Copyright &y& Elsevier]