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multiferroic materials with unique properties of porous ceramics, such as high surface area, high strength and high chemical resistivity, could open up a new field of study in advanced materials [ 5 ]. Bismuth ferrite, BiFeO₃ (BFO), is perhaps the only multiferroic material with a coexistence of ferroelectric and magnetic ordering at room temperature [ 6 ]. BiFeO₃ possesses a rhombohedrally distorted perovskite structure with R3c space group, high ferroelectric Curie temperature (TC ~ 830 °C) and G-type antiferromagnetic Neel temperature (TN ~ 370 °C). Since BiFeO₃ is very

Abstract

The aim of this work was to prepare BiFeO3 by modified solid-state sintering and mechanical activation processes and to investigate the structure and hyperfine interactions of the material. X-ray diffraction and Mössbauer spectroscopy were applied as complementary methods. In the case of sintering, BiFeO3 phase was obtained from the mixture of precursors with 3 and 5 % excess of Bi2O3 during heating at 1023 K. Small amounts of impurities such as Bi2Fe4O9 and sillenite were recognized. In the case of mechanical activation, the milling of stoichiometric amounts of Bi2O3 and Fe2O3 followed by isothermal annealing at 973 K resulted in formation of the mixture of BiFeO3, Bi2Fe4O9, sillenite and hematite. After separate milling of individual Bi2O3 and Fe2O3 powders, mixing, further milling and thermal processing, the amount of desired BiFeO3 pure phase was significantly increased (from 70 to 90 %, as roughly estimated). From Mössbauer spectra, the hyperfine interaction parameters of the desired BiFeO3 compound, paramagnetic impurities of Bi2Fe4O9 and sillenite were determined. The main conclusion is that the lowest amount of impurities was obtained for BiFeO3 with 3 % excess of Bi2O3, which was sintered at 1023 K. However, in the case of mechanical activation, the pure phase formed at a temperature by 50 K lower as compared to solid-state sintering temperature. X-ray diffraction and Mössbauer spectroscopy revealed that for both sintered and mechanically activated BiFeO3 compounds, thermal treatment at elevated temperature led to a partial eliminating of the paramagnetic impurities.

Abstract

Nondoped BiFeO3 (BFO) and doped Bi0.9La0.1Fe0.9Mn0.1O3 (BLFMO) thin films (d = 200–350 nm) were grown at 650–750 °C by RF sputtering on Si and SrTiO3(100), coated by conductive LaNiO3 films and La2/3Ca1/3MnO3/SrRuO3 bilayers. The complex dielectric permittivity of the films was measured at room temperature in the frequency range from 10 MHz to 10 GHz using parallel plate capacitor structures. Dielectric properties of the polycrystalline BFO films were compared with those of the epitaxial quality BLFMO films, and it was seen that the latter has better microwave performance than the former. The dielectric losses were below 0.05 at 1 GHz frequency, which may be acceptable for microwave applications.

. Radiosensitization of Prostate Cancers In Vitro and In Vivo to Erbium-filtered Orthovoltage X-rays Using Actively Targeted Gold Nanoparticles. Scientific Reports. 2017;7:18044. [5] Sung W, Schuemann J. Energy optimization in gold nanoparticle enhanced radiation therapy. Phys Med Biol. 2018;63(13):135001. [6] Rajaee A, Wensheng X, Zhao L, et al. Multifunctional Bismuth Ferrite Nanoparticles as Magnetic Localized Dose Enhancement in Radiotherapy and Imaging. J Biomed Nanotechnol. 2018;14(6):1159-1168. [7] Kuncic Z, Lacombe S. Nanoparticle radio-enhancement: principles, progress and

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