Papers by Keyword: Bismuth Ferrite

Abstract: This study assesses the photovoltaic potential of pure Bismuth Ferrite (BiFeO₃) and its doped variants, specifically Samarium (Sm)-doped and Cobalt–Samarium (Co–Sm) co-doped BiFeO₃ nanoparticles. The materials were synthesized using sol-gel methods, followed by post-annealing to promote high crystallinity. A comprehensive characterization was performed to evaluate the structural, morphological, and optical properties utilizing X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), and UV-Vis spectroscopy. The findings indicate that doping and co-doping have a substantial influence on the optical bandgap, particle morphology, and crystallite dimensions. Sm and Co–Sm doping reduced the bandgap, enhancing visible-light absorption and solar energy-harvesting efficiency, whereas pure BiFeO₃ exhibited a bandgap of 2.03 eV. Electrical investigations further revealed greater charge separation, underscoring the superior charge-transport properties of the modified materials. The results indicate that doped BiFeO₃ systems hold potential as tunable multiferroic materials for advanced, high-efficiency solar applications.

Abstract: Bismuth ferrite nanoparticles were successfully synthesized by the co-precipitation method and modified by polyethylene glycol (PEG) 4000. X-ray diffraction patterns showed a sillenite structure of bismuth ferrite (Bi₂₅FeO₄₀) with a crystallite size of 35.0 nm and the new phase appeared after surface modification. The new phase was Bi₂Fe₄O₉. Crystallite size increased after surface modification of nanoparticles with PEG. The highest increase of crystallite size after surface modification with PEG was 40.1 nm. Transmission electron microscopy images showed that samples before and after surface modification were polycrystalline and still agglomerated. Spectra of Fourier transform infrared showed the presence of C-O stretching at 1080 cm^-1 and C-H bending vibration at 1342 cm^-1 in the bismuth ferrite/PEG sample, which did not appear in bismuth ferrite sample. The magnetic measurement indicated the weak ferromagnetic properties of the samples. Saturation magnetization did not appear after a maximum external magnetic field (15 kOe) was applied. The maximum magnetization of nanoparticles was 0.5 emu/g and tended to decrease to 0.2 emu/g after surface modification with PEG. Optical properties analysis showed a shift in the maximum absorption peak of bismuth ferrite nanoparticles towards a lower wavelength (blue shift) after surface modification of the nanoparticles. The specific absorption rate (SAR) value of nanoparticles increased by increasing an alternating magnetic field (AMF) strength. The SAR values of bismuth ferrite nanoparticles were 48.8, 61.4, and 84.4 mW/g and decreased to 32.0, 45.2, and 83.3 mW/g after surface modification at the AMF strength of 150, 200, and 250 Oe, respectively.

Abstract: In this work, single phase Bismuth Ferrite, BiFeO₃ was successfully synthesized by using hydrothermal method assisted with different weight (0.24 g, 0.36 g and 0.48 g) of Chitosan. Potassium hydroxide (KOH) were used as a mineralizer during the synthesis process for the precipitation. The samples were characterized for different properties such as structural and optical properties, and were then compared with previous works. The X-ray diffraction data for all the samples showed that the samples had a single phase belonging to R3c space group with perovskite rhombohedral structure at diffraction angle 32.0° to 32.5° even though the slight presence of secondary phase at diffraction angle 28° was detected. Scanning electron microscope revealed a decrement in particle size as the weight of Chitosan increased indicating effective used of Chitosan in controlling the agglomeration of the particles. All samples BiFeO3 assisted with and without Chitosan showed significant enhancement in energy gap where the obtained results showed a small energy gap values ranging from ~1.22 eV to ~1.88 eV determined from UV-vis absorbance characterization. Therefore, by the addition of Chitosan, the properties of BiFeO₃ such as structural and optical have changed as well as preventing from the particle to agglomerate.

Abstract: Among other multiferroic materials, bismuth ferrite (BiFeO₃) attracts much attention due to its room-temperature properties and its wide potential applications. However, the synthesis to obtain a single-phase material is hard to be achieved because of the volatility of bismuth oxide. In this study, the BiFeO₃ powders were synthesized by using a sol-gel method from the nitrates of bismuth and iron salt with the various stoichiometric ratios between Bi and Fe of 1:1.02, 1:1, 1.02:1, and 1.03:1. The single-phase and a good stoichiometric ratio of Bi: Fe = 1:1 was obtained from the starting composition ratio of 1.03:1 with a quenching process from 550°C sintering temperature. The single-phase of BiFeO₃ shows a hysteresis curve of a weak antiferromagnetic with a coercive field of about 1.38 kOe at room temperature. The measurement of microwave oscillator was measured by using a dielectric resonator from 0 to 25 GHz does not show any resonant peak.

Abstract: Bismuth ferrite (BiFeO₃) nanoparticles has been synthesized by coprecipitation method with various NaOH concentration (4, 6, 8, and 10 M) and temperature (RT, 60, 80, and 100 C). X-ray diffraction patterns showed the emergence of Bi(OH)₃ and Bi₂₅FeO₄₀ structures with crystallite size in the range of 15.1 nm to 35.6 nm. The particles sample was agglomerated. Hysterisis loop showed the linear M–H loops behaviour with no magnetization saturation in 15 kOe maximum field applied which indicates the antiferromagnetic properties. The coercivity field tends to increase by the increasing of the NaOH concentration and synthesis temperature. In addition, the annealing treatment could leads the increasing of coercivity fields while decreasing the magnetization of BFO sampel.

Abstract: Nanocrystalline bismuth ferrite BFO; BiFeO₃ and manganese sillenite, BMO; Bi₁₂MnO₂₀ (BMO) powders have been successfully elaborated using a facile co-precipitation approach. The formed materials were examined using X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM). Furthermore, the change in the optical properties was performed based on Fourier transform infrared spectroscopy (FT-IR) and UV-visible spectrophotometer. Typical, pure BiFeO₃ and Bi₁₂MnO₂₀ phases were detected for the precursors precipitated at pH 10 based on ammonium hydroxide as a base then annealed at 500°C for 2h. Eventually, the optical band gap energy of BFO and BMO using Kubelka–Munk function based on Tauc’s plot was found to be 2.12 and 2.79 eV, respectively.

Abstract: (Bi₂O₃Fe₂O₃)_0.8(Nb₂O₅)_0.2 was synthesized by solid state reaction method. (Bi₂O₃Fe₂O₃)_0.8(Nb₂O₅)_0.2 was made for the investigation of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Dielectric property. XRD pattern reveals that three phases were obtained with Bismuth Iron Niobium Oxide. SEM elicits that grain size increases with the enhancement of sintering temperature. Dielectric property decreases with the augmentation of frequency.

Abstract: NiO/BiFeO₃ thin film has been deposited on Pt/Ti/SiO₂/Si substrate by sol-gel method. The structure of thin film is analyzed by X-ray diffraction, and the result of X-ray diffraction shows that a perovskite crystal structure can be well-grown on Pt/Ti/SiO₂/Si substrate. In addition, the surface morphology is characterized by a scanning probe microscope, and the image of scanning probe microscope indicates a good crystalline quality of NiO/BFO thin film. Moreover, the current-voltage properties are also measured by a semiconductor characterization system, and the stable and reproducible nonvolatile resistive switching characteristic for the memory application have been clearly observed in Pt/NiO/BiFeO₃/Pt structure, which could be attributed to the formation and rupture of filament localized in NiO thin layer.

Abstract: Multiferroic films of BiFeO₃, (BiLa)FeO₃ and (BiNd)FeO₃ with various concentration of ions of Bi, La and Nd in dodecahedral sublattice utilising were fabricated on monocrystalline substrates of (001) SrTiO₃, (100) MgO and (100) Al₂O₃ by a number of technological methods: rf sputtering, vacuum laser ablation and metal-organic chemical vapor deposition (MOCVD). The film thickness varied in the range of 30-300 nm. The magnetic and magnetoelectric properties of the obtained films were investigated. The saturation magnetization of BiFeO₃ was about 9 emu/cm³ which is typical of strained films of this composition. Doping BiFeO₃ films by rear earth ions La (Nd) increases both the magnetisation saturation and Neel temperature, as well as magnetoelectric effects, which is explained by increase in magnetic crystal anisotropy and suppression of spatially modulated magnetic structure. It was demonstrated that the corona discharge treatment resulted in a substantial growth of the magnetisation saturation up to 35% whereas the changes in the Neel temperature were not noticible. This is explained by the induced electret state and giant magnetoelectric effect.

Abstract: Bismuth ferrite is an important material in ferroelectric photovoltaic field, because of its narrow band gap and large polarization. Doping is a common method to further improve the photovoltaic properties of bismuth ferrite. Mn-doped bismuth ferrite thin films were prepared by sol-gel method. The effects of manganese on the crystal structure, ferroelectric and photovoltaic properties have been investigated. The result indicates that Mn-doped bismuth ferrite thin films are single phase and the lattice constant increases with the increase of manganese content. As manganese content increases, the remnant polarization and coercive electric field increase, while the short circuit photocurrent density and power conversion efficiency decrease. The open circuit photovoltage increases first and reaches the maximum and then decreases as manganese content increases. The results indicate that enhanced ferroelectricity caused by addition of manganese doesn’t make improvement on the photovoltaic characteristic.