Dielectric and impedance spectroscopy of (Ba, Sm)(Ti, Fe)O_3 system in the low-medium frequency range

摘要

The (Ba, Sm)(Ti, Fe)O_3 system, combination of non-ferroelectric samarium ortho-ferrite and ferroelectric barium titanate, was prepared by using a standard high-temperature solid-state reaction technique. Structural analysis of the material using room temperature XRD data confirmed the formation of the single-phase compound. Detailed structural analysis of the system using Rietveld refinement method exhibits the tetragonal structure with polar space group P4mm. Room temperature micrograph of the sample recorded by a scanning electron microscope shows uniform distribution of grains of various dimension and with less voids confirming the formation of high density sample. Studies of dielectric and impedance spectroscopy characteristics of the sample were carried out in the low-frequency (100-1300 mHz) and the high-frequency region (100 Hz-1 MHz) at different temperatures (25-300 ℃). The frequency dependence of dielectric constant of both low and high frequency plots was explained on the basis of Maxwell-Wagner mechanism, Shockley Read statistics and Koops phenomenological theories. Ferroelectric phase transition appears in both the low- and high-frequency regions. Nyquist plots show the contributions of grain, grain boundary and electrode effect. The frequency dependence of conduction mechanisms were explained on the basis of correlated barrier hopping model and overlapping large polaron tunneling models. The P-E hysteresis loop confirms the ferroelectricity in the material.