Ashima

Bio: Ashima is an academic researcher from Guru Jambheshwar University of Science and Technology. The author has contributed to research in topics: Dielectric & Rietveld refinement. The author has an hindex of 6, co-authored 6 publications receiving 395 citations.

Rietveld analysis, dielectric and magnetic properties of Sr and Ti codoped BiFeO3 multiferroic

Abstract: Polycrystalline Bi0.8Sr0.2Fe1 − xTixO3 (x = 0.0, 0.1, 0.2) multiferroics were synthesized via the conventional solid state reaction method. The structure, dielectric relaxation, and magnetic properties of as prepared samples were investigated. The crystal structure examined via XRD and Rietveld analysis confirmed a single phase rhombohedral (space group R3c no. 161) structure. In the Rietveld refinement, good agreement between the observed and calculated pattern was observed. The dielectric response of these multiferroics was analyzed in the frequency range of 10 Hz to 5 MHz at different temperatures. All the samples showed dispersion in dielectric constant (έ) and dielectric loss factor (tan δ) values. The temperature dependence of έ and tan δ showed broad peaks. A reduction in the values of έ and tan δ was observed upon the incorporation of Ti. Magnetic measurements were carried out at room temperature up to a field of 20 kOe. Magnetic hysteresis loops revealed a significant increase in magnetization with Ti substitution. A remnant magnetization (Mr) of 33.428 memu/g and a coercive field (Hc) of 1.724 kOe were observed in the sample with x = 0.2.

Structural transformation and improved dielectric and magnetic properties in Ti-substituted Bi0.8La0.2FeO3 multiferroics

Abstract: Ti-substituted BiLaFeO3 ceramics having compositions Bi0.8La0.2Fe1?xTixO3 (x?=?0.0, 0.05, 0.1, 0.15) were synthesized by the conventional solid-state reaction method. Powder x-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x?=?0.0, 0.05; tetragonal for x?=?0.15; and a phase boundary occurs at x?=?0.1. In the Rietveld refinement good agreement between the observed and calculated pattern was observed. Dielectric response of these samples was analysed in the frequency range 1?kHz?5?MHz at different temperatures. A decrease in the values of real (??) and imaginary (??) parts of dielectric constant with Ti substitution indicates reduced conductivity and hence enhanced resistivity in doped samples. Stability of dielectric constant and conductivity with temperature is considerably improved with Ti substitution. Magnetic measurements were carried out at room temperature up to a field of 20?kOe. Magnetic properties of Bi0.8La0.2FeO3 ceramics are considerably improved on Ti substitution along with a significant opening in the room temperature M?H hysteresis loop. Higher values of remanent magnetization (Mr) 0.1373 and 0.1487?emu?g?1; coercivity (Hc) 4.856 and 5.904?kOe are observed for samples with x?=?0.1 and 0.15, respectively. This is due to the structural phase transition from rhombohedral to tetragonal.

Phase transformation, dielectric and magnetic properties of Nb doped Bi0.8Sr0.2FeO3 multiferroics

Abstract: Bi0.8Sr0.2Fe1−xNbxO3 (x = 0.0, 0.05, and 0.10) multiferroics were prepared by solid state reaction method. X-ray diffraction and Rietveld analysis show that crystal structure is rhombohedral for x = 0.0, 0.05 samples and triclinic for x = 0.10 sample. These samples showed dispersion in dielectric constant (έ) and dielectric loss (tan δ) values at lower frequencies. For x = 0.05 sample, both έ and tan δ are lower than for Bi0.8Sr0.2FeO3 sample indicating its high resistivity. For x = 0.10 sample, the value of έ is enhanced which may be due to formation of stronger dipoles in triclinic structure. Temperature dependence of frequency exponent “s” of power law suggests that correlated barrier hopping (CBH) model is applicable at lower temperatures and quantum mechanical tunneling model is appropriate at higher temperatures for describing the conduction mechanism in x = 0.0 and x = 0.05 samples; while in x = 0.10 sample, CBH model is appropriate in studied temperature range. Significant enhancement observed in magnetization for x = 0.10 sample is due to the structural phase transition from rhombohedral to triclinic caused by Nb substitution. For this sample, values of remnant magnetization (Mr) and coercive field (Hc) are 0.155 emu/g and 2.695 kOe, respectively.

Improved dielectric and magnetic properties of Ti modified BiCaFeO3 multiferroic ceramics

Abstract: Ti substituted BiCaFeO3 ceramics having compositions Bi0.8Ca0.2Fe1−xTixO3 (x = 0.0, 0.1, 0.2) were synthesized by the conventional solid state reaction method. Powder X-ray diffraction investigations performed at room temperature show that all samples possess a rhombohedrally distorted perovskite structure described by the space group R3c. Rietveld refinement presented a good agreement between the observed and calculated patterns. Dielectric response of these samples was analyzed in the frequency range 1 kHz–5 MHz at different temperatures. Dispersion in dielectric constant (έ) and dielectric loss factor (tanδ) values decreases with Ti substitution. έ increases and tanδ decreases significantly by Ti substitution. Magnetic measurements were carried out at room temperature up to a field of 20 kOe. Magnetic properties of Bi0.8Ca0.2FeO3 ceramic are greatly improved on Ti substitution along with a significant opening in the room temperature M-H hysteresis loop. The values of remnant magnetization (Mr) 0.08 and...

The Gadolinium (Gd 3+ ) and Tin (Sn 4+ ) Co-doped BiFeO 3 Nanoparticles as New Solar Light Active Photocatalyst.

Abstract: The process of photocatalysis is appealing to huge interest motivated by the great promise of addressing current energy and environmental issues through converting solar light directly into chemical energy. However, an efficient solar energy harvesting for photocatalysis remains a critical challenge. Here, we reported a new full solar spectrum driven photocatalyst by co-doping of Gd3+ and Sn4+ into A and B-sites of BiFeO3 simultaneously. The co-doping of Gd3+ and Sn4+ played a key role in hampering the recombination of electron-hole pairs and shifted the band-gap of BiFeO3 from 2.10 eV to 2.03 eV. The Brunauer-Emmett-Teller (BET) measurement confirmed that the co-doping of Gd3+ and Sn4+ into BiFeO3 increased the surface area and porosity, and thus the photocatalytic activity of the Bi0.90Gd0.10Fe0.95Sn0.05O3 system was significantly improved. Our work proposed a new photocatalyst that could degrade various organic dyes like Congo red, Methylene blue, and Methyl violet under irradiation with different light wavelengths and gave guidance for designing more efficient photocatalysts.

Structural, magnetic, and optical properties of Pr and Zr codoped BiFeO3 multiferroic ceramics

Abstract: Single-phase (Bi1-xPrx)(Fe1-xZrx)O3 ceramics with x = 0.03, 0.06, 0.10 (named BPFZ-3, BPFZ-6, and BPFZ-10, respectively) were synthesized by solid state reaction method. X-ray diffraction suggested the pure phase formation with distorted rhombohedral structure in all samples. Raman spectroscopy also confirmed the rhombohedrally distorted perovskite structure with R3c symmetry. The x-ray photoelectron spectroscopy measurements showed the absence of Fe2+ ions indicating the suppression of oxygen vacancies due to Pr and Zr codoping. Room temperature magnetic hysteresis loops revealed that the spontaneous magnetization increases due to structural distortion and partial destruction of spiral spin structure caused by the codoping in BiFeO3 ceramics. The maximum remnant magnetization of 0.1234 emu/g was observed for BPFZ-6 sample. Optical studies showed absorption of light in the visible region, with a red shift in energy band gap with increasing concentration of Pr and Zr in BiFeO3 ceramics. The broad absorptio...