Optical, dielectric relaxation and conduction study of Bi2Fe4O9 ceramic

Abstract

Abstract:Multiferroic bismuth ferrite Bi2Fe4O9 (BFO) ceramic was synthesized by conventional solid state reaction route. X-ray diffraction and Rietveld refinement show formation of single phase ceramic with orthorhombic crystal structure (space group 'Pbam'). The morphological study depicted a well-defined grain of size ~2μm. The optical studies were carried out by using UVVis spectrophotometer which shows a band gap of 1.53 eV and a green emission spectrum at 537 is observed in the Photoluminescence study. The frequency dependent dielectric study at various temperature revealed that the dielectric constant decreases with increase in frequency.A noticeable peak shift towards higher frequency with increasing temperature is observed in the frequency dependent dielectric loss plot. The impedance spectroscopy shows a substantial shift in imaginary impedance (Z") peaks toward the high frequency side described that the conduction in material favoring the long range motion of mobile charge carriers. The presence of non-Debye type multiple relaxations has been confirmed by complex modulus analysis. The frequency dependent ac conductivity at different temperatures indicates that the conduction process is thermally activated. The variation of dc conductivity exhibited a negative temperature coefficient of resistance behavior. The activation energy calculated from impedance, modulus and conductivity data confirmed that the oxygen vacancies play a vital role in the conduction mechanism.

Electrical properties of bismuth ferrites: Bi2Fe4O9 and Bi25FeO39

“…However, the conductivities reported in [42] were attributed to the presence of oxygen vacancies for which we find no evidence from the C' data, Figs. 3,4(c).…”

“…Hysteresis data have been reported [32,34,39] in which the polarization-electric field curves tend to give oval rather than ferroic-shaped hysteresis loops and in one report [39], it was stated that the P-E curves were 'characteristic of very poor ferroelectric materials'. Bi 2 Fe 4 O 9 presents catalytic activity under visible light irradiation [40][41], with a band gap of about 1.53 eV [42].…”

Complex Dielectric and Impedance Spectroscopic Studies in a Multiferroic Composite of Bi2Fe4O9-BiFeO3

“…The normalized plot of M" as well as Z" is shown in Figure 9, which shows a non-coincident of frequency of occurrence of maxima, which implies two different phenomena contributing for the relaxation in the modulus and impedance, respectively. This indicates the non-Debye type behavior of the system in the temperature range of 423 K-623 K [28]. The relaxation time is the time required for the recombination of charges till the capacitor is fully discharged during which the field is no longer applied.…”

“…The ac conductivity (σac) study signifies the presence of single or multiple relaxation in the material. In this case, the ac conductivity plot with respect to frequency at different temperatures (cf Figure 10) can be divided into a low frequency plateau governed by random hopping of electrons contributing to dc conductivity and a high frequency dispersive region dependent upon ω n (where ω is the angular frequency and n is a constant dependent upon frequency and temperature) and defines the type of conductivity [28] related to the hopping of electrons between trap levels situated in the bandgap [25]. Conductivity plots are fitted well with Joanscher's power law, σ ac = σ dc + Aω n [29].…”

Investigation of Structural, Electrical, and Vibrational Properties of Bi1.98A0.02Fe4O9 (A = Ba, Ce) Multiferroic Ceramics

“…Few authors reported hysteresis data [5,12,13] in which the P-E field curves tend to give oval rather than ferroic-shaped hysteresis loops. Bi 2 Fe 4 O 9 with a band gap of about 1.53 eV presents catalytic activity under visible light irradiation [14,15]. Sol-gel processing, which gives a polycrystalline material, can control particle size of the crystallized phase and can eliminate any pores.…”