The relaxation processes of dielectric, modulus and impedance in Dy0.55Sr0.45Mn1- xFexO3

Abstract

The ac electrical properties of orthorhombic ceramics, Dy0.55Sr0.45Mn1-xFexO3 (x = 0, 0.4 and 1.0) in the range of frequency 0.5–107 Hz and temperature 126–299 K have been studied. Across the series, dielectric permittivity and loss increase with increase in Fe concentration. Non-Debye type dielectric relaxation peak was found in x = 0.4 compound among Dy0.55Sr0.45Mn1-xFexO3 materials and consequently activation energy of the dielectric relaxation was calculated. The results of impedance spectroscopy revealed that for higher concentration of Fe in the series, impedance (Z′) is low. The relaxation peaks in impedance, Z″ are observed at different frequency ranges for different Fe concentration in the compounds. From the temperature dependence of these peaks, activation energies are determined. The results of modulus spectra indicated a similar behavior as impedance, but x = 0.4 compound showed a large activation energy among the compounds in the series. Cole-Cole plots displayed negative temperature coefficient of resistance, a normal behavior of semiconductors. These plots also suggested that the dielectric relaxation is of non-Debye type. The scaling behavior in the modulus and impedance suggested that temperature dependence of relaxation processes exists in these materials. These studies and results are significant for materials which exhibit high resistance in low temperature.