Electrical conductivity and vibrational studies induced phase transition in [N(C3H7)4]2ZnBr4 compound

Abstract

Bis-Tetrapropylammonium tetrabromozincate was synthesized and characterized by X-ray powder diffraction, as well as vibrational and impedance spectroscopy. Rietveld’s refinement of X-ray diffractogram confirmed the crystallization of the compound through the monoclinic system (space group C2/c). A temperature study of Raman scattering revealed two phase transitions at approximately T1 = 340 K and T2 = 393 K. The wavenumber and the line width’s evolution as a function of temperature showed some peculiarities associated with these transitions, which suggests that they are governed by the reorientation of the organic part [N(C3H7)4]+. The complex impedance plotted as a double semicircular arc in the studied temperature range and the centers of these semicircles lie below the real axis, which indicates that the material is an on-Debye type. These semicircular arcs are related to the bulk and the grain boundary effects. Furthermore, the alternating current conductivity of [N(C3H7)4]2ZnBr4 obeyed Jonscher’s law: σAC(ω) = σdc + Aωs and the conduction could be attributed to the correlated barrier hopping (CBH) model in both region(I) and (II) and the Non-overlapping Small Polaron Tunneling (NSPT) in region (III).

Keywords

• bis-tetrapropylammonium tetrabromozincate
• raman spectroscopy
• phase transition
• electrical conductivity
• conduction mechanism