Structural, AC conductivity, dielectric and impedance studies of polypyrrole/praseodymium calcium manganite nanocomposites

Abstract

In-situ polymerization of a series of nanocomposites viz. 10, 20, 30, 40 and 50 wt % of Praseodymium Calcium Manganite Oxide (Pr0.75Ca0.25MnO3) (PCM) nano manganites in polypyrrole (PPy) were prepared by chemical polymerization technique. The crystalline nature of all the nanocomposites was confirmed by powder X-ray diffraction (XRD). The orthorhombic structure with space group Pnma was confirmed by the well-fitted Rietveld refined XRD data. The average particle size was observed to be in the range of 42 to 60 nm. Scanning Electron Microscope (SEM) confirmed the spherical nature of the particles. The TEM confirmed the crystallinity and Fourier Transform Infra-Red Spectroscopy (FTIR) showed that the stretching frequencies shifted towards higher frequencies for the nanocomposites suggesting better conjugation due to chemical interaction between the PPy and PCM particles. AC conductivity versus frequency showed that at higher frequencies the AC increases obeying Jonscher’s power law. The correlated barrier hopping (CBH) model is therefore used to describe the conduction mechanism. For all composites, the dielectric constant and tangent loss revealed a frequency- and temperaturedependent character. The real and imaginary impedance were both frequency and temperature dependent. The impedance data were analyzed by fitting Nyquist plots using ZsimpWin software which confirmed non Debye type of behavior. This study highlights on the interactions between conduction processes, grain boundaries, and grains.