Synthesis, crystal structure, phase transition and electrical conduction mechanism of the new [(C3H7)4N]2MnCl4 compound

Abstract

Bis tetrapropylammonium tetrchloro-monganete has been synthesized and characterized by X-ray, differential scanning calorimetry, vibrational spectroscopy and impedance spectroscopy. At room temperature, the latter is crystallized in the monoclinic phase, with P2/c space group. The projection of atomic arrangement along b axis shows that all nitrogen atoms are disposed linearly along [001] direction. Differential scanning calorimetry (DSC) disclosed three order–disorder phase transitions at T1=333K, T2=356K and T3=379K. Besides, impedance measurements indicate that the electrical and dielectric properties are strongly dependent on both temperature and frequency. Nyquist plots (Z″ versus Z′) show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a series combination of grains interior and grains boundary. The evolution of the dielectric constant as a function of temperature shows a distribution of relaxation times which is probably due to the reorientational dynamics of alkyl chains. On the other hand, the dependency of m(T) with temperature has been discussed in terms of the correlated barrier hopping (CBH) model in phase (I and IV). The quantum mechanical tunneling (QMT) model describes the second phase (II), whereas the third one (III) is characterized by the non-overlapping small Polaron tunneling (NSPT) model.