Using Raman spectroscopy to understand the origin of the phase transitions observed in [(C₃H₇)₄N]₂Zn₂Cl₆ compound

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

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 (P6₃ mc 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.

Monitoring dehydration of the organic-inorganic [(C3H7)4N][SnCl5(H2O)]·2H2O compound using simultaneous thermal and Raman studies

In this work we report the experimental studies of the structural phase transition in the [(C3H7)4N]SnCl5(H2O)]·2H2O compound by differential scanning calorimetric (DSC) and Raman spectroscopic. The X-ray powder diffraction study of the [(C3H7)4N][SnCl5(H2O)]·2H2O sample at room temperature showed that this compound is monoclinic and has P121/c1 space group. Differential scanning calorimetric disclosed two types of phase transitions in the temperature range 356-376 (T1) K and at 393K (T2) characterized, by a loss of water molecules and probably a reconstruction of new anionic parts after T2 transition. The Raman scattering spectra recorded at various temperatures in the wavenumber range from 100 to 3800cm(-1) covering the domains of existence of changes in the vicinity of the two phase transitions detected by DSC measurement. A detailed study of the spectral parameters (wave number, reduced intensity and the full width at half maximum) as a function of temperature of a chosen band, associated with (νs(SnO)+νs(SnCl)), based on an order-disorder model allowed us to obtain information relative to the activation energy and correlation length.

Conduction mechanism model, impedance spectroscopic investigation and modulus behavior of the organic–inorganic [(C3H7)4N][SnCl5(H2O)]·2H2O compound

In this study, the electric properties and modulus formulation of the compound [(C₃H₇)₄N][SnCl₅(H₂O)]·2H₂O were studied in the 200 Hz to 5 MHz frequency range and the 343–418 K temperature range.