Electrical analysis and molecular dynamics of anion in ferroelastic [(CH3)4P]2CoBr4 crystal near high-temperature phase transitions

Abstract

The recent technological advances require an aligned innovation in the materials used for the construction of electronic devices. Hybrid materials play a important role in the optoelectronic applications because they combine both the organic and inorganic components. To this end, the [(CH3)4P]2CoBr4 compound was successfully synthesized using the slow evaporation solution growth approach at room temperature. In-depth research has been conducted on the structural, morphological, vibrationnal and electrical characteristics. The [(CH3)4P]2CoBr4 compound crystallises in the monclinic system with P121/C1 space group. The examination of SEM images reveals that the majority of grains have an average size of around 4 μm with irregularly shaped and non-spherical particles. The measured Raman spectra demonstrate the coexistence of two transition phases located at 373 K and 428 K. In fact, these observations suggest that the anionic components play a significant role in influencing the phase transitions mechanism. Analysis of the complex impedance spectra reveals that the electrical characteristics of the material is strongly dependent on both frequency and temperature. That indicates the existence of a relaxation phenomenon and of a semiconductor-type behavior. One single semicircle is detectable in the Nyquist plots of the complex impedance spectra, which can be satisfactorily fitted with a combination of R//C//CPE elements assigned to the bulk response. Therefore, we can conclude from this behavior that the sample is electrically homogeneous. The dependency of s(T) on temperature also shows that the correlated barrier hopping and the non-overlapping small polar on tunneling model are the responsible mechanisms for the AC conduction in [(CH3)4P]2CoBr4.