K. Saravana Kumar

Role of oxygen vacancy and Fe–O–Fe bond angle in compositional, magnetic, and dielectric relaxation on Eu-substituted BiFeO3 nanoparticles

The influence of oxygen vacancies on the dielectric relaxation behavior of pure and Eu-substituted BiFeO3 nanoparticles synthesized by a sol-gel technique has been studied using impedance spectroscopy in the temperature range of 90 °C to 180 °C. The electric relaxation time and activation energy of the oxygen vacancies can be calculated from the Arrhenius equation, and found to be 1.26 eV and 1.76 eV for pure and Eu-substituted BiFeO3, respectively. Substitution induces structural disorder and changes in the Fe-O-Fe bond angle, leading to alteration of the magnetic properties, observed from magnetic studies and evaluated using Rietveld refinement of the XRD patterns. X-ray photoelectron spectroscopy (XPS) confirms the shifting of the binding energy of the Bi 4f orbital, establishing Eu substitution at the Bi site. Calculation of the area under the Fe(2+)/Fe(3+) (2p) and O (1s) XPS spectra gives approximate values of the oxygen vacancies.

Mechanical milling assisted synthesis of Ba?Mn co-substituted BiFeO3 ceramics and their properties

Samples of composition Bi1−xBaxFe1−xMnxO3 (x = 0, 0.1, 0.2) were synthesized by initial mixing of precursors by high-energy ball milling and subsequent sintering of the milled powders. The co-substitution of Ba–Mn controls the formation of impurity phases, as evident from x-ray diffraction analysis. Evidence of Fe in mixed oxidation states of +3 and +2 and Mn in +3 state is found from x-ray photoelectron spectroscopy. Electron microscopy exhibits a decrease in grain size due to inhibition in grain growth by Ba–Mn co-substitution. The magnetization value at 20 kOe increases as the percentage of substitution increases. The x = 0.2 sample exhibits a comparable and stable resistivity curve in the experimental temperature range and has a higher value of remanent polarization (Pr) when compared with the x = 0 sample.

Effect of Fe substitution on the magnetic properties of BiMn2O5

Powders of BiFeMnO5, by the substitution of Fe ions at Mn3+ sites of parent BiMn2O5 system, were synthesized by a two-step process: initial high-energy ball milling of oxides in zirconia vials and then sintering of the as-milled powders. BiFeMnO5 has orthorhombic structure (Pbam) as that of the parent system, determined from x-ray diffraction. Above 850??C it melts and transforms to a multi-phase system. Smaller particle size is observed from scanning electron microscopy in comparison with parent BiMn2O5. Thermo-magnetization studies indicate a Neel transition around 40?K. Isothermal magnetization measurements reveal paramagnetic nature at room temperature and a weak ferromagnetic property below the transition temperature. As an effect of Fe substitution in BiMn2O5, a significant increase in coercivity (Hc) and decrease in remanent magnetization (Mr) are observed below transition temperature which is discussed based on the dynamics of exchange interaction.

Synthesis and study of Bi0.9Tb0.1Fe0.9Mn0.1O3 ceramics

The (Tb, Mn) co-substituted BiFeO3 samples were synthesized by the combined high-energy ball milling and sintering process. XRD study shows the formation of stoichiometric phase of rhombohedral (R3c) structure with minor impurity peaks. Particle size distribution with irregular morphology is observed from scanning electron microscopy. Room temperature magnetization measurement shows a hysteresis like behaviour without saturation, which is due to the suppression of spiral spin structure by co-substitution.

Synthesis and Characterization of BiMn2O5 Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .

Synthesis and Characterization of BiMn2O5Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .

Synthesis and Characterization of BiMn[sub 2]O[sub 5] Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .