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Journal ArticleDOI

Electrical conductivity and vibrational studies induced phase transitions in [(C2H5)4N]FeCl4

04 Dec 2018-RSC Advances (The Royal Society of Chemistry)-Vol. 8, Iss: 71, pp 40676-40686
TL;DR: In this paper, the tetraethylammonium tetrachloroferrate (C2H5)4N]FeCl4 was characterized by X-ray powder diffraction, thermal analysis, and impedance and vibrational spectroscopy.
Abstract: The compound, tetraethylammonium tetrachloroferrate [(C2H5)4N]FeCl4, was prepared by slow evaporation at room temperature. It was characterized by X-ray powder diffraction, thermal analysis, and impedance and vibrational spectroscopy. X-ray diffraction data confirmed formation of a single phase material which crystallized at room temperature in the hexagonal system (P63mc space group). DSC showed the existence of two phase transitions at 413 K and 430 K. Electrical conductivity was measured in the temperature and frequency ranges of 390 K to 440 K and 40 Hz to 110 MHz, respectively. Nyquist plots revealed the existence of grains and grain boundaries that were fitted to an equivalent circuit. AC conductivity plots were analyzed by Jonscher's power law. Variations in the “s” values indicated that CBH models describe the conduction mechanism in regions I and II. Temperature dependence of Raman spectra showed that the most important changes were observed in the cationic parts ([(C2H5)4N]+). The activation energy value obtained from the line width decreased which indicated an order–disorder model.

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Citations
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Journal ArticleDOI
TL;DR: In this article, a new organic-inorganic hybrid material, tetrapropylammonium tetrachloferrate, has been synthesized and characterized by single-crystal X-ray diffraction, thermal analysis, vibrational and impedance spectroscopies.

18 citations

Journal ArticleDOI
TL;DR: In this article, the [(C2H5)4N]FeCl4 compound was successfully synthesized using a slow evaporation solution growth method at room temperature, and an optical absorption measurement confirmed the semiconductor nature with a band gap around 2.95 eV.
Abstract: The alkylammonium halogenoferrate families are subjected to diverse studies according to their wide field application. However, these compounds show various transitions depending on the preparation process. In this paper, the [(C2H5)4N]FeCl4 compound was successfully synthesized using a slow evaporation solution growth method at room temperature. An optical absorption measurement confirms the semiconductor nature with a band gap around 2.95 eV. The X-ray powder diffraction (XRPD) data confirmed the formation of a single-phase with hexagonal-type structure. The differential scanning calorimetry (DSC) indicated that the [(C2H5)4N]FeCl4 compound undergoes eight reversible phase transitions between 193 and 443 K. At high temperature (T > 423 K) the plastic nature of the crystals was confirmed. Temperature-controlled X-ray diffraction reveals that the thermal expansion of the crystal structure is non homothetic in the (a,b) plane and along the c axis. The temperature dependence of the Raman spectra up to 443 K revealed specific reorientations and molecular displacements of the organic and inorganic components associated with the phase transitions. We aim to thermally stabilize the [(C2H5)4N]FeCl4 compound which has a band gap suitable for photocatalytic processes.

5 citations

Journal ArticleDOI
TL;DR: In this article, a compound of Rubidium magnesium monophosphate (RbMgPO4) was synthesized using the solid−state method and two phase transitions of a ferroelectric nature were investigated using Raman spectroscopy analysis.

5 citations

Journal ArticleDOI
TL;DR: In this article, the Hirshfeld surfaces and fingerprint plots were used to analyse quantitatively the interactions in the crystal structure of (C6H5NH3)2ZnCl4.H2O.

4 citations

References
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Journal ArticleDOI
TL;DR: In this article, the main formulas governing the analysis of the Bragg magnetic scattering are summarized and shortly discussed and the method of profile fitting without a structural model to get precise integrated intensities and refine the propagation vector(s) of the magnetic structure is discussed.
Abstract: In spite of intrinsic limitations, neutron powder diffraction is, and will still be in the future, the primary and most straightforward technique for magnetic structure determination. In this paper some recent improvements in the analysis of magnetic neutron powder diffraction data are discussed. After an introduction to the subject, the main formulas governing the analysis of the Bragg magnetic scattering are summarized and shortly discussed. Next, we discuss the method of profile fitting without a structural model to get precise integrated intensities and refine the propagation vector(s) of the magnetic structure. The simulated annealing approach for magnetic structure determination is briefly discussed and, finally, some features of the program FullProf concerning the magnetic structure refinement are presented and discussed. The different themes are illustrated with simple examples.

11,923 citations

Journal ArticleDOI
TL;DR: In this article, the authors propose a vectorial chemistry approach for the generation of new generations of hybrid materials, which will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.
Abstract: Organic–inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol–gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, etc. The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, etc.) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.

2,321 citations

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TL;DR: In this article, a comprehensive survey is given of the experimental a.c. data for two types of amorphous semiconductor, namely chalcogenide and pnictide materials, and it is concluded that the behavior at intermediate to high temperatures is well accounted for by the correlated-barrier-hopping model, whereas the low-temperature behaviour is probably due to atomic tunnelling.
Abstract: The various origins of a frequency-dependent conductivity in amorphous semiconductors are reviewed, stressing particularly recent advances and the influences that factors such as correlation and non-random spatial distributions of electrically active centres can have on the a.c. conductivity. A comprehensive survey is given of the experimental a.c. data for two types of amorphous semiconductor, namely chalcogenide and pnictide materials. It is concluded that the a.c. behaviour at intermediate to high temperatures is well accounted for by the correlated-barrier-hopping model, whereas the low-temperature behaviour is probably due to atomic tunnelling.

1,814 citations

Journal ArticleDOI
TL;DR: In this article, complex dielectric constants have been measured at frequencies from below 20 c/s to 5 mc/s over the temperature range −40° to −75°C in glycerol, −45°-to −90° in propylene glycol, and −80°-140° in npropanol.
Abstract: Complex dielectric constants have been measured at frequencies from below 20 c/s to 5 mc/s over the temperature range −40° to −75°C in glycerol, −45° to −90° in propylene glycol, and −80° to −140° in n‐propanol. The results for n‐propanol are described by the Debye equation, but the values for the other two require a modified equation corresponding to a broader range of dispersion at higher frequencies. In all three liquids, evidence is found for a second dispersion region at still higher frequencies, which accounts for much of the difference between the radio frequency and optical dielectric constant. The relaxation times are quantitatively described over wide ranges by an empirical rate equation of a form which also fits viscosity data. The significance of the various results is discussed.

1,681 citations

Journal ArticleDOI
S. Havriliak1, S. Negami1
TL;DR: In this paper, the authors measured and analyzed the complex dielectric behavior of the α-dispersions for five polymers [i.e., polycarbonate and polyisophthalate esters of bisphenol A, isotactic poly-(methyl methacrylate), poly(methyl acrylate) and a copolymer of phenyl methacellitrile] and found that the usual methods of analysis cannot be used to represent the data.
Abstract: The α-dispersion in many polymer systems is the process to be associated with the glass transition temperature where many physical properties undergo drastic changes. We have measured and analyzed the complex dielectric behavior of the α-dispersions for five polymers [i.e., polycarbonate and polyisophthalate esters of bisphenol A, isotactic poly-(methyl methacrylate), poly(methyl acrylate), and a copolymer of phenyl methacrylate and acrylonitrile] and have found that the usual methods of analysis cannot be used to represent the data. However, it is possible to represent the relaxation process as the sum of two dispersions but there is no evidence to support this contention. An empirical expression is proposed to represent the data. This expression which takes the form of appears to be a general representation for the three known dispersions, i.e., Debye, circular arc, and skewed semicircle. The complex dielectric constants calculated with the aid of this expression and the parameters for each polymer system which was determined graphically were found to be in excellent agreement with the experimental complex dielectric constants. This method of representation was extended to sixteen α-dispersions reported in the literature always with excellent results.

1,503 citations