Electrical characterization and vibrational spectroscopic investigations of order-disorder phase transitions in [N(C3H7)4]2CoCl4 compound.

The present paper accounts for the vibrational spectroscopy and electrical characterization of a bis - tetrapropylammonium tetrachlorocobaltate grown at room temperature by slow evaporation of aqueous solution. The Raman spectra were studied in the range of 50–3500 cm −1 as a function of temperature of 318 K–421 K. The most important changes are observed for the band at 1032 cm −1 associated to δ ( C − C − C ) + t ( C H 2 ) + ω ( C H 2 ) . A detail analysis of the frequency and half-width is quantitatively described in term of an order-disorder model allowed to obtain information relative to the thermal coefficient and activation energy. The decrease of the activation energy with increasing temperature has been interpreted in term of a change in the re-orientation motion of the cationic parts [N(C 3 H 7 ) 4 ] + . Besides, the impedance measurements indicate that the electrical properties are strongly temperature dependent. Nyquist plots (−Z″versus Z′) show that the conductivity behavior is accurately represented by an equivalent circuit models which consists of a series combination of grains interior and grains boundary. The conductivity follows the Arrhenius relation with different activation energies and conduction mechanisms: three temperature regions with activation energies E a I = 0.78 eV and E a II = 0.81 eV and E a III = 0.93 eV. Furthermore, the modulus plots can be characterized by full width at half height or in term of a non-experiential decay function ϕ ( t ) = exp ( − 1 τ ) β . [ABSTRACT FROM AUTHOR]