Dielectric relaxations and dielectric response in multiferroic BiFeO3 ceramics

Abstract

Single-phase multiferroic BiFeO3 ceramics were fabricated using pure precipitation-prepared BiFeO3 powder. Dielectric response of BiFeO3 ceramics was investigated over a wide range of temperature and frequency. Our results reveal that the BiFeO3 ceramic sintered at 700 °C exhibited high dielectric permittivity, and three dielectric relaxations were observed. A Debye-type dielectric relaxation at low temperatures (−50 to 20 °C) is attributed to the carrier hopping process between Fe2+ and Fe3+. The other two dielectric relaxations at the temperature ranges 30–130 °C and 140–200 °C could be due to the grain boundary effect and the defect ordering and/or the conductivity, respectively.

Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

“…At temperatures higher than~350°C the conductivity increases rapidly with activation energy of 1.26 eVand its low-frequency values become higher than those for the high frequency [23]. Another dielectric behaviour with three relaxation processes have been reported for the ceramics sintered at 700°C during 4 h from pure precipitation-synthesized BFO powder [25]. The low-temperature relaxation with activation energy of 0.34 eV was attributed by the authors to the hopping conductivity of the localized charge carriers, the middletemperature relaxation process of the activation energy 0.77 eV was related to the grain boundary effect, whereas the high-temperature relaxation with the highest activation energy (0.95 eV) to the defects and/or the conduction.…”

“…We discover that the obtained ceramics exhibits a high dielectric permittivity. It has been established that three dielectric relaxation processes contribute to the dielectric response in the temperature range 125-575 K. X-ray diffraction (XRD) analysis reveal the presence of a trace of Bi 25 FeO 40 and we understand that the parasitic phase plays an important role in the observed dielectric properties. The electrical inhomogeneity of the material enables us to justify the relatively giant value of dielectric permittivity using the well-known internal barrier layer capacitor model [4,5,8].…”

“…It should however be noted that the dielectric response and electric conductivity of BFO ceramics are determined by the processing conditions [21][22][23][24][25], which are responsible not only for the oxygen deficiency and the presence of Fe 2+ but also for the formation of various parasitic phases [26,27]. BFO ceramics obtained by rapid liquid phase sintering [21,22] as well as ceramics sintered from coprecipitation powder at 800°C and 850°C [23] are single-phased ceramics of a high electric resistivity with ferric Fe 3+ ions.…”

Giant magnetoelectric coupling interaction in BaTiO3/BiFeO3/BaTiO3 trilayer multiferroic heterostructures

“…14 In the trilayer film with 20 nm BFO layer, two distinct regions of activation energies were observed with E a $ 0.24 eV (T < 353 K) corresponding to second ionization energy of oxygen vacancy and E a $ 0.39 eV at higher temperature, which is close to the activation energy corresponding to the two site electron hopping between Fe 2þ and Fe 3þ ions. 29 The calculated activation energy E a $ 0.26 eV for B-2, E a $ 0.19 eV for B-4, and E a $ 0.11 eV for B-8 all over the investigated temperature range corresponds to the ionization energy of oxygen vacancies. It indicates the sizeable coupling between oxygen vacancy and Fe-ions through localized electrons in thinner films, which may be due to higher concentration of oxygen vacancies.…”

Dielectric response and magnetoelectric coupling in single crystal gallium ferrite

“…Further from the plot of ln τ IMP IB vs. 1000/T as shown in Fig. 3(a) 20 While Fe valence fluctuation in Fe containing transition metal oxides is quite common, our room temperature Mössbauer data (not shown here) on our GFO samples did not show the presence of Fe divalent state and thus ruling out the possibility of aforementioned electron transfer in GFO. Another possibility of the observed activation energy could be the relaxation due the movement of charged oxygen vacancies which are likely to be formed during high temperature oxide material synthesis as per following reactions:…”