Study on the structural and electrical properties of YMnO3 co-substituted with transition metal ions at Mn-site and their conduction mechanism

Rare earth manganite YMnO3 and YMn0.9Cr0.06Fe0.04O3 wherein transition metal ions are co-substituted at Mn-sites, were synthesized via sol–gel auto combustion route. The present work aims to study the effect of Cr3+ and Fe3+ co-substitution at Mn-site of YMnO3, on their structural and electrical properties. The structural and morphological studies were performed using X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM). The XRD pattern confirmed the existence of monophasic hexagonal structure for YMnO3 while the onset of few orthorhombic peaks was observed for YMn0.9Cr0.06Fe0.04O3. The A1 Raman scattering line at ∼ 676 cm−1 was observed to be much stronger than the other Raman modes. Uniform and dense morphological structure were observed in the FESEM micrographs. Enhanced dielectric properties were observed in the substituted sample. The frequency dependence of AC conductivity was investigated using Jonscher’s law. Non-overlapping small polaron tunnelling model was predicted for the conduction model in YMnO3 and correlated barrier hopping in YMn0.9Cr0.06Fe0.04O3 to elucidate the conduction mechanism of the system. The activation energy for intrinsic charge carriers was calculated using Arrhenius equation. The impact of grains and grain boundaries on the electrical behaviour of the samples was validated by fitting the Nyquist plot.