Investigation of conduction and relaxation phenomena in LaFe0.9Ni0.1O3 by impedance spectroscopy

Polycrystalline LaFe0.9Ni0.1O3 is prepared by the solid state reactions route. X-ray diffraction is used to analyse the phase purity of the compound. Impedance spectra of LaFe0.9Ni0.1O3 over the frequency range of 1 Hz to 10 MHz are investigated at different temperatures from 100 to 373 K. Two relaxation processes with different relaxation times are observed at each temperature. An equivalent circuit model (R(1)Q(1)) (R(2)Q(2)) is applied to explore the physical parameters associated with grains and grain boundaries. Frequency and temperature dependence of the relaxation processes and extracted parameters are discussed in terms of hopping between Fe+4 and Fe+3 and trap state scattering at grain boundaries. A change in conduction mechanism from variable range hopping to adiabatic small polaron hopping at 296 K is evident from these results. Traps are active below 296 K in capturing the charge.