Synthesis and structure of BiFeO3:RE (RE=Gd3+, Dy3+, Nd3+) ceramics

In the present work the influence of rare earth elements concentration (0-10at-%) on BiFeO3:RE (RE=Gd3+, Dy3+, Nd3+) ceramics were studied. All ceramic powders were synthesized by conventional ceramic method using high purity raw materials (>99,9%), and subsequently sintered by free sintering and cold pressing method. To analyze the powders and ceramics more the XRD, EDS, SEM, and DTA were performed

ZALEŻNOŚĆ CZĘSTOTLIWOŚCIOWA NAPIĘCIOWEGO WSPÓŁCZYNNIKA MAGNETOELEKTRYCZNEGO W CERAMIKACH (BiFeO3)x-(BaTiO3)1-x

Composition-dependent magnetoelectric properties of sintered (BiFeO3)x-(BaTiO3)1-x ceramics have been recently observed and reported in the literature. Measurements of the magnetoelectric effect (ME) for these materials have been performed by usage of the dynamic method. The samples with x = 0.9, 0.8 and 0.7 were placed in a static (DC) magnetic field created by an electromagnet on which a sinusoidal (AC) magnetic field with a frequency of 1 kHz produced by Helmholtz coils was superimposed. In this work the theory of the dynamic measurement was presented and the optimal frequency of the AC field was determined in order to minimize the processes causing undesired reduction of the measured voltage signal.Zależność właściwości magnetoelektrycznych od składu chemicznego w ceramikach (BiFeO3)x-(BaTiO3)1-x została w ostatnim czasie zaobserwowana i odnotowana w literaturze. Pomiary efektu magnetoelektrycznego (ME) w tych materiałach wykonywane były metodą dynamiczną. Próbki o x = 0,9, 0,8 i 0,7 umieszczano w stałym (DC) polu magnetycznym generowanym przez elektromagnes, na które nałożono zmienne (AC) pole magnetyczne o częstotliwości f = 1kHz wytwarzane przez cewki Helmholtza. W niniejszej pracy przedstawiono podstawy teoretyczne tego rodzaju pomiarów oraz wyznaczono optymalną częstotliwość pola AC, która minimalizuje procesy powodujące redukcję mierzonego sygnału napięciowego

Magnetoelectric Effect in Ceramics Based on Bismuth Ferrite

Solid-state sintering method was used to prepare ceramic materials based on bismuth ferrite, i.e., (BiFeO3)1 − x–(BaTiO3)x and Bi1 − xNdxFeO3 solid solutions and the Aurivillius Bi5Ti3FeO15 compound. The structure of the materials was examined using X-ray diffraction, and the Rietveld method was applied to phase analysis and structure refinement. Magnetoelectric coupling was registered in all the materials using dynamic lock-in technique. The highest value of magnetoelectric coupling coefficient αME was obtained for the Bi5Ti3FeO15 compound (αME ~ 10 mVcm−1 Oe−1). In the case of (BiFeO3)1 − x–(BaTiO3)x and Bi1 − xNdxFeO3 solid solutions, the maximum αME is of the order of 1 and 2.7 mVcm−1 Oe−1, respectively. The magnitude of magnetoelectric coupling is accompanied with structural transformation in the studied solid solutions. The relatively high magnetoelectric effect in the Aurivillius Bi5Ti3FeO15 compound is surprising, especially since the material is paramagnetic at room temperature. When the materials were subjected to a preliminary electrical poling, the magnitude of the magnetoelectric coupling increased 2–3 times

Microstructure, XRD and Mössbauer spectroscopy study of Gd doped BiFeO3

The results of fabrication process and characterization of Bi1-xGdxFeO3 (x = 0.05, 0.07, 0.10) ceramics are reported in the paper. The samples were prepared by standard solid state reaction method from the mixture of oxides: Bi2O3, Fe2O3 and Gd2O3. The influence of Gd substitution on the microstructure and density of Bi1-xGdxFeO3 was studied. Phase composition and structure of the obtained samples were investigated by Xray diffraction. It turns out that the Bi1-xGdxFeO3 solid solutions with x = 0.05 and 0.07 crystallize in trigonal structure characteristic of BiFeO3 compound. For the sample with x = 0.1, beside the major trigonal phase, 6% of orthorhombic phase typical for GdFeO3 was detected. Hyperfine interaction parameters were studied by Mössbauer spectroscopy. Mössbauer results proved that the spin cycloid characteristic of BiFeO3 compound gradually disappears when substituting Gd3+ ions at the Bi3+ sites

The Effect of Ho Doping Contents on the Structural, Microstructure and Dielectric Properties of Bi5Ti3FeO15 Aurivillius Ceramics

Aurivillius Bi5-xHoxTi3FeO15 (BHTFO) multiferroic ceramics with different holmium doping contents were synthesized by conventional solid state reaction. The effect of holmium doping on the microstructure, structural and dielectric behaviors of BHTFO ceramics were investigated in details. Microstructure and crystalline structure studies of ceramics were carried out at room temperature while dielectric properties were investigated in a wide range of temperature (T = 25ºC-550ºC) and frequency (20Hz-1MHz)

Atrial fibrillation genetic risk differentiates cardioembolic stroke from other stroke subtypes

AbstractObjectiveWe sought to assess whether genetic risk factors for atrial fibrillation can explain cardioembolic stroke risk.MethodsWe evaluated genetic correlations between a prior genetic study of AF and AF in the presence of cardioembolic stroke using genome-wide genotypes from the Stroke Genetics Network (N = 3,190 AF cases, 3,000 cardioembolic stroke cases, and 28,026 referents). We tested whether a previously-validated AF polygenic risk score (PRS) associated with cardioembolic and other stroke subtypes after accounting for AF clinical risk factors.ResultsWe observed strong correlation between previously reported genetic risk for AF, AF in the presence of stroke, and cardioembolic stroke (Pearson’s r=0.77 and 0.76, respectively, across SNPs with p &lt; 4.4 × 10−4 in the prior AF meta-analysis). An AF PRS, adjusted for clinical AF risk factors, was associated with cardioembolic stroke (odds ratio (OR) per standard deviation (sd) = 1.40, p = 1.45×10−48), explaining ∼20% of the heritable component of cardioembolic stroke risk. The AF PRS was also associated with stroke of undetermined cause (OR per sd = 1.07, p = 0.004), but no other primary stroke subtypes (all p &gt; 0.1).ConclusionsGenetic risk for AF is associated with cardioembolic stroke, independent of clinical risk factors. Studies are warranted to determine whether AF genetic risk can serve as a biomarker for strokes caused by AF.</jats:sec

Effect of BaTiO3 concentration on structural and magnetic properties of mechanically activated BiFeO3-BaTiO3 system

In this research, the mechanical activation method is proposed as an alternative process of preparation of the (BiFeO3)1-x-(BaTiO3)x solid solutions with various concentrations of barium titanate (x = 0.1÷0.9). However, mechanical milling itself does not allow obtaining the desired products and additional thermal treatment is needed to complete the solid-state reaction. In the present studies, X-ray diffraction and 57Fe Mössbauer spectroscopy were applied as complementary methods in order to study the structural and magnetic properties of materials. The investigations revealed that an increase of BaTiO3 concentration causes changes in the crystalline and hyperfine magnetic structure of the studied (BiFeO3)1-x-(BaTiO3)x system

Synthesis and characterization of AgFeO2 delafossite with non-stoichiometric silver concentration

The simple co-precipitation method was used to prepare AgxFeO2 delafossite with non-stoichiometric silver concentration in the range of x = 0.05-1. The obtained material was investigated using X-ray powder diffraction and 57Fe Mössbauer spectroscopy at room temperature. The structural and hyperfi ne interaction parameters were recognized in relation with decreasing silver concentration. The study revealed that the delafossite structure of AgxFeO2 was maintained up to x = 0.9; as the range of silver concentration was decreased to 0.05 ≤ x ≤ 0.8, a mixture of AgFeO2, Fe2O3 or/and FeOOH was formed

Superconductivity in high-entropy alloy system containing Th

Abstract Th-containing superconducting high entropy system with the nominal composition (NbTa) $$_{0.67}$$ 0.67 (MoWTh) $$_{0.33}$$ 0.33 was synthesized. Its structural and physical properties were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific heat, resistivity and magnetic measurements. Two main phases of alloy were observed: major bcc structure and minor fcc. The experimental results were supported by numerical simulation by the DFT Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA)

Structure and Mössbauer spectroscopy studies of mechanically activated (BiFeO3)1−x-(BaTiO3)x solid solutions

(BiFeO3)1-x-(BaTiO3)x solid solutions with x = 0.1–0.4 and 0.7 were investigated. The ceramics were prepared by mechanical activation technology and subsequent heat treatment. As was proved by X-ray diffraction, increase of BaTiO3 concentration causes a change in the crystalline structure from the rhombohedral structure characteristic of BiFeO3 to a cubic one. 57Fe Mössbauer spectroscopy allowed observation of a gradual transformation from an ordered spin structure of Fe3+ ions to the paramagnetic state with an increase of x