Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

Abstract

Dielectric behaviour of BiFeO 3 ceramics, obtained by hot-pressing of nanopowders produced by mechanochemical synthesis from Bi 2 O 3 and Fe 2 O 3 oxides (weight ratio 2:1), was studied in the temperature range 125-575 K. The ceramics was found to exhibit step-like dielectric response ε*(T) with high permittivity values, similar to the behaviour of materials with giant dielectric permittivity. Three overlapping relaxation processes contribute to the dielectric response: i) relaxation in the lowtemperature range (220-420 K), characterized by activation energy of 0.4 eV, ii) relaxation in the temperature range 320-520 K with activation energy of 1.0 eV and iii) broad dielectric anomaly in the vicinity of 420 K, which disappears after 1 h annealing at 775 K. The lowtemperature relaxation is ascribed to the carrier hopping process between Fe 2+ and Fe 3+ ions. The presence of mixed valence of the Fe ions was proved by X-ray photoelectron spectroscopy. Dielectric relaxation in the middle-temperature range is considered as a result of grain boundary effect and internal barrier layers related to Bi 25 FeO 40 phase as verified by X-ray diffraction. The high-temperature dielectric anomaly we relate to short-range hopping of ordered oxygen vacancies.

Frequency-dependent decoupling of domain-wall motion and lattice strain in bismuth ferrite

“…For {100} pc grains, a higher relative permittivity is used, in this case a value of 40 is adopted for the model, considering that the transverse permittivity of a number of rhombohedral ferroelectrics with a 3 m symmetry (isostructural with BiFeO 3 ) is higher than the longitudinal permittivity 46 . The as-reported bulk electrical conductivity of BiFeO 3 ceramics and single crystals at room temperature are spread over several orders of magnitude, typically between ~10 −2 and ~10 −10 Ω −1 m −1 32 , 47 – 49 . The conductivity in the range of 10 −9 –10 −10 Ω −1 m −1 was used in the calculations, consistent with the measured bulk electrical conductivity of our BiFeO 3 sample as shown in Supplementary Figure 7 , and can reproduce the main features of the microscopic strains (the data shown in the main paper are relative conductivity of σ 111 = 100 and σ 100 = 250 for {111} pc grain and {100} pc grain, respectively).…”

Study of the Structural and Electrical Properties of Cr-Doped BiFeO<sub>3</sub> Ceramic

“…Materials with high dielectric permittivity values, so-called giant permittivity, reaching ε′- 10 5 , have been widely investigated because of their various applications in the microelectronic industry [1].…”

Dielectric and magnetic properties of (Bi1-xLaxFeO3)0.5(PbTiO3)0.5 ceramics prepared by high energy mechanochemical technique

“…Bismuth ferrite BiFeO 3 (BFO), a single phase multiferroic at room temperature, with antiferromagnetic-paramagnetic transition temperature T N = 640 K and ferroelectric Curie point at T C =1098 K, is one of the most extensively studied materials. The range of its application is however, restricted because of weak magnetoelectric coupling, high electric conductivity, comparable thermodynamic stability of Fe 2+ and Fe 3+ ions, very narrow temperature range of crystallization (between T C and eutectic point at 1058 K) and volatility of Bi 2 O 3 starting oxide [6][7][8][9][10][11]. At room temperature, the magnetic properties of BFO are determined by the structure of G-type with a cycloidal spiral arrangement of the magnetic moments of Fe 3+ ions with the period λ≈ 62 nm and canted spins due to the Dzyaloshinskii-Moriya interaction [12][13][14].…”