Raman scattering and alternative current conduction mechanism of the different phase transitions in [(CH3)(3)NH]CoCl3 center dot 2H(2)O

摘要

The trimethylammonium cobalt chloride dihydrate was obtained by slow evaporation at room temperature. The behavior in accordance with temperature variation was sought. The Rietveld refinement of the X-ray powder diffraction pattern led to the formation of a pure phase which crystallizes in the orthorhombic system with the Pnma space group. Three endothermic peaks at T-1 = 310 K, T-2 = 349 K, and T-3 = 358 K were evidenced by DSC measurements. In order to characterize the phase transitions and their nature, Raman spectra were recorded in the frequency range related to the vibrations of the cations and anions (10-3600 cm(-1)). The results obtained show the utility of the Raman spectra to probe the changes in T-1 and then the reconstruction of new anionic parts after T-2 transition. The analysis of the line width based on the order-disorder model was used to obtain information concerning the activation energy near the phase transition at T-1.