Mossbauer Spectroscopy Research Articles

NMR and Mossbauer studies of core–shell FeCo@C ferromagnetic nanoparticles near the superparamagnetic transition

A series of nanoparticles of the bimetallic core and carbon shell type FexCo1-x@C (x = 0.4 – 0.8) have been obtained by the gas condensation synthesis method. The microstructural peculiarities and magnetic behaviour of the nanoparticles is analysed depending on the composition and thermal treatment. Collateral phases, which are difficult to detect by traditional methods, are identified. The 59Co,57Fe NMR and 57Fe Mossbauer spectroscopies have shown that homogeneity of the composition and removal of carbon from the metallic core can be reached by annealing. The combination of methods has quantified the fraction of superparamagnetic particles, the proportion of paramagnetic inclusions. A simplified visual interpretation of the 59Co NMR spectra is proposed for binary FeCo alloys.

A Review on Measurement Techniques of Deformation‐Induced Transformation Kinetics in Transformation‐Induced Plasticity and Transformation‐Induced Plasticity‐Assisted Steels

Deformation‐induced austenite‐to‐martensite transformation is an important phenomenon that controls the flow behavior of transformation‐induced‐plasticity (TRIP) and TRIP‐assisted steels. Transformation kinetics and triggering strain are important parameters that need to be known during transformation. Both these parameters can be correctly determined by an accurate quantitative assessment of the austenite during deformation. Herein, both in situ and ex situ measurement techniques used for quantitative assessment of austenite during/after tensile deformation of the TRIP and TRIP‐assisted steels are reviewed. A comparison of various techniques such as X‐ray diffraction, neutron diffraction, Mossbauer spectroscopy, and DC/AC magnetic permeability is presented. Due to limited penetration power of the radiations, difficult access, and difficulty in setting up the measurement facility for the in situ measurements, X‐ray diffraction, neutron diffraction, and Mossbauer spectroscopy techniques do not yield accurate quantitative results and are time‐consuming. It is envisaged that an accurate quantitative assessment of austenite from the bulk of TRIP and TRIP‐assisted steel specimens is possible with magnetic permeability measurement techniques. Real‐time quantitative assessments can be made by measuring changes in the magnetic permeability due to changes in the ferromagnetic content during deformation. magnetic permeability measurements require extensive calibration for the accurate measurement of the phases during deformation of the steel.

Ultrathin Fe Films Sandwiched Between Au Layers: CEMS- study

The STM studies of Fe films with thickness above 0.6 ML do not contribute significantly to the solution of the structural problems, because of the Au surface layer, which hinders details of the Fe sub-surface layers. The Mossbauer spectroscopy appears in this case as an exceptional method, which has the ability to solve structural and magnetic problems. Our discussion is based on a simplified spectrum analysis, assuming a discrete character of the spectral components. In reality, a distribution of the hyperfine magnetic field, as well as isomer shift and the quadrupole splitting is an obvious and natural consequence of the finite size system 'presented by the monolayer film. The exact fitting of all hyperfine parameters distribution is too difficult. Most of the fitting procedures treat the distributions of IS vs. Bhf and QS vs. Bhf as linearly dependent as described using the well-known Voigt-based method.

Study of structure, cation distribution and magnetic properties of Ni substituted M-type barium hexaferrite

In the present work, BaFe12-xNixO19 (x = 0, 0.1, 0.3, 0.5) powders were prepared by the hydrothermal method with post annealing. The obtained samples were analyzed by several methods, including XRD, Mossbauer spectroscopy, EDX, VSM, and AFM. Structural and elemental analyses confirm that Ni enters the hexaferrite lattice. Since Ni2+ replaces Fe3+, some charge compensation mechanism must be involved. According to the data obtained, the most probable mechanism is the formation of oxygen vacancies. Based on the results of Mossbauer spectroscopy and magnetic measurements, the cation distribution was established. The Ni2+ ions prefer to occupy the 12k site, which leads to a decrease in the saturation magnetization. All magnetic parameters (saturation magnetization, coercivity, and remanence) correlate negatively with the Ni concentration.

Occupancies of tetra- and octahedral sites in CoFe2O4 nanoparticles: The effect of the sintering temperature

A temperature factor is one of the main parameters in the synthesis of nanoparticles and can affect considerably the arrangement of atoms in the lattice. In the system of magnetically hard CoFe2O4 spinel ferrite, the distribution of cations directly determines the magnetic properties of the sample. It was studied, on products of co-precipitation synthesis followed by a temperature dependent sinterization, by x-ray diffraction (XRD), x-ray absorption (XAS) using synchrotron radiation, vibrating sample magnetometry, and 57Fe Mössbauer spectroscopy (MS). From the Rietveld refinement of XRD patterns, the site occupancies reveal the following trend: with a decrease in the sintering temperature, the inversion degree parameter γ, which is a fraction of Co ions residing in the octahedral sites, decreases. For the highest sintering temperature explored in this work, 1000 °C, γ ≈ 0.83 giving rise to (Co0.17Fe0.83)A[Co0.83Fe1.27]BO4 formulation. For the lowest sintering temperature explored, 500 °C, the inversion degree is approximately 0.69 giving rise to (Co0.31Fe0.69)A[Co0.69Fe1.31]BO4 formulation. The propensity for the cationic arrangement was also confirmed by MS. Qualitative analysis of XAS at Co L3,2 edges strongly supports the tendency observed by XRD: the lower the sintering temperature, the more Co ions tend to occupy the tetrahedral sites. The magnetic behavior of the samples is consistent with the particle size which was determined by transmission/scanning electron microscopies. The particle size is the product of different sintering temperatures after the primary synthesis.

Development of a cell for in-situ/operando Mössbauer spectroscopy studies of Catalysts: Application to the characterization of iron nanoparticles used in Fischer-Tropsch reaction.

In this paper, we report the design of a stainless-steel cell with polyimide film windows for carrying out in situ Mossbauer spectroscopy studies with a horizontal x-ray beam. It allows recording spectra at pressures up to 0.2-0.3 MPa and temperatures up to 500 °C under a gas flow rate of up to 100 ml min-1. The catalyst is either directly deposited on the heating element or pressed into the form of a pellet for larger quantities. A wide range of heating or cooling rates can be used, and a very accurate sample temperature can be monitored for several days. An example of application to the study of a catalyst based on iron nanoparticles entrapped in silicalite-1 used for the Fischer-Tropsch reaction is presented to illustrate the use of the cell.

Structurally dependent electroconductivity properties of ultrafine composites α-FeOOH/α-Fe2O3

In articles first time to presents approach to obtaining of ultrafine defective composite α-FeOOH/α-Fe2O3 by hydrothermal synthesis and investigated the influence of post-processing on phase transformations, magnetic microstructure and elecroconductivity. The X-ray analysis, Mossbauer spectroscopy, IR spectroscopy and impedance spectroscopy used to analyzed the structural-morphological and elecroconductivity. It was established that the selection of the parameters of the synthesis to possible the control of the processes of nucleation, aggregation and restructuring of the formed defective composite. Theories of thermo-induced reorganization of different phase structures and the formation of the intrinsic semiconductorness as a result of internal activation are updated.

The Structure-Performance Relation for Alkaline OER Electrocatalyst Investigated Using Analytical Electron Microscopy

Water electrolysis technology plays a key role in reducing carbon emission by converting renewable energy to clean hydrogen. Among various types of electrolyzers, anion exchange membrane water electrolyzer (AEMWE) receives growing effort of research due to its potential of comparable power density as its counterpart, proton exchange membrane water electrolyzer (PEMWE), while offering less corrosive environment on the oxygen evolution electrode which permits the use of non-noble metal catalysts [1].Nickel-iron oxides/hydroxides are among the most active electrocatalysts for oxygen evolution reaction (OER) in alkaline environment [2]. Recently, aerogel-like Ni-Fe oxides developed at Los Alamos National Laboratory have shown promising performance in AEMWE. The modified sol-gel approach followed by drying under supercritical condition produces high-surface-area oxides which likely contributes to high OER activity with enhanced number of active sites compared to other synthesis methods [3].In this work, we aim to elucidate the structure-performance relation for aerogel-like Ni-Fe oxides. Analytical electron microscopy methods, namely, energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) are used to investigate the distribution of Fe in the oxides and the oxidation states of Ni and Fe. The effect of annealing temperature in air on the oxide structure and OER activity has been investigated. Moreover, the structural changes before and after catalyst activation and long-term operation at OER potentials have been studied. Finally, results from analytical electron microscopy have been correlated with X-ray absorption spectroscopy and 57Fe Mossbauer spectroscopy to obtain a comprehensive picture of the oxide composition, especially the chemical environment of Fe.

Universal Synthesis of Half-Metallic Diatomic Catalysts for Efficient Oxygen Reduction Electrocatalysis.

Developing efficient and low-cost noble-free metal electrocatalysts is an urgent requirement. Herein, a one-step, solid-state template-assisted method for fabricating isolated half-metallic diatomic M, Zn─N─C (M═Fe, Co, and Ni) catalysts is reported. In particular, the fabricated Fe, Zn─N─C structure exhibits superior oxygen reduction reaction capabilities with a half-wave potential of 0.867V versus RHE. The Mossbauer spectra reveal that the Fe, Zn─N─C half-metallic diatomic catalyst has a large proportion of the D2 site (ferrous iron with a medium spin state). Density functional theory (DFT) reveals that in Fe, Zn─N─C structures, the zinc sites play a unique role in accelerating the protonation process of O2 in ORR. In assembled zinc-air batteries, a maximum power density of 138mWcm-2 and a capacity of 748 mAhgzn-1 can be obtained. This work fabricates a series of efficient M, Zn─N─C diatomic electrocatalysts, and the developed solid-state reactionmethod can hopefully apply in other energy conversion and storage fields.

FeOOH and (Fe,Zn)OOH hybrid anion exchange adsorbents for phosphate recovery: A determination of Fe-phases and adsorption–desorption mechanisms

Hybrid anion exchange adsorbents (HAIX) seem promising to prevent eutrophication and recover phosphate (P). HAIX consist of an anion exchange resin (AIX) backbone, promoting anion physisorption (outer-sphere complex), impregnated with iron (hydr)oxide nanoparticles (NPs), for selective P chemisorption (inner-sphere complex). In this work, for the first time, as far as we know, Zn-doped iron (hydr)oxide NPs were embedded in AIX, and the performances compared with conventional HAIX, both commercial and synthesized. Zn-doped HAIX displayed improved P adsorption performances. Mössbauer spectroscopy (MS) revealed the goethite nature of the NPs, against the “amorphous hydrous ferric oxide” claimed in literature. The P adsorption comparisons, made in synthetic solution and real wastewater, underlined the crucial role of the NPs for selective P adsorption, while improving the understanding on the competition between physisorption and chemisorption. In pure P synthetic solutions, especially at high P concentrations, physisorption can “hide” chemisorption. This depends also on the anion form of the AIX, due to their higher affinity for multivalent anions, which affects HAIX adsorption selectivity and P desorption. In fact, a mild alkaline regeneration over three adsorption–desorption cycles revealed a complex interaction between the regenerant OH− and the adsorbed P. OH− molecules are consumed to transform phosphate speciation, causing (stronger) P re-adsorption and preventing desorption. Finally, Mössbauer spectroscopy revealed NPs agglomeration/growth after the three cycles plus final regeneration at pH 14. This study provides further understanding on the P adsorption–desorption mechanism in HAIX, drawing attention on the choice of experimental conditions for reliable performance assessment, and questioning HAIX consistent P removal and efficient P recovery in the long-term.

Comparative study between Ni–Co ferrite and multi rare earth element doped Ni–Co ferrite

This paper reports the synthesis and analysis of structural, spectral, dielectric and magnetic properties of nano sized multi rare earth (RE) element doped Ni0.5Co0.5Gd0.002Tb0.002Dy0.002Ho0.002Er0.002Fe1.99O4 (NCFR5). The structural and functional properties of this compound was compared with the parent Ni0.5Co0.5Fe2O4 (NCF). Ni0.5Co0.5Fe2O4 and Ni0.5Co0.5Gd0.002Tb0.002Dy0.002Ho0.002Er0.002Fe1.99O4 with five different heavy rare earth elements at octahedral B-site were successfully synthesized by sol–gel method. X-ray diffraction measurements supported the spinel ferrites' single-phase formation. With doping, the lattice parameter was increased from 8.218 Ao to 8.243 Ao. Evaluation of Rietveld refinement of NCF and NCFR5 samples was done. Scanning electron microscopy surface morphology studies revealed the existence of nanoscale grains for both compositions. The existence of five RE elements in NCFR5 was proved by ICP MS analysis. Room temperature UV Diffuse Reflectance Spectroscopy was performed on NCF and NCFR5, and it was discovered that NCFR5 had a greater direct bandgap than NCF. To comprehend the distribution of ions in A and B sites, Raman and Mossbauer spectroscopy were used. It was discovered that rare earth doping significantly affected the magnetic and dielectric characteristics. Multi RE element doping increased strain sensitivity in NCFR5.

Synthesis, structural and magnetic study of BaFe12O19/CoFe2O4@CoFe2 nanocomposites

Cooperative effects in hybrid nanocomposites are an interesting field of research. The behavior of magnetic nanocomposites is the result of spatial arrangements of phases and their magnetic correlations through exchange and dipolar forces. Understanding these influences is an important task in order to produce magnetic composites with improved properties. In this work, we present a study on the structural and magnetic properties of nanocomposites made of barium hexaferrite (BaFe12O19) coated either with cobalt ferrite spinel (CoFe2O4) or core-shell CoFe2O4@CoFe2 nanoparticles, i.e. BaFe12O19/CoFe2O4 or BaFe12O19/CoFe2O4@CoFe2. The BaFe12O19 (BFO) phase was produced using the ionic coordination reaction technique and then coated with CoFe2O4 (CFO) nanoparticles synthesized by the polyol method. Several concentrations of the BFO and CFO phases were considered. The BFO/CFO samples were reduced in hydrogen gas, where partial reductions of cobalt ferrite give rise to the alloy CoFe2 (CF). Thus, we produced a new nanocomposite of the type BFO/CFO@CF. These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Mössbauer spectroscopy (ME). The XRD and ME analyzes revealed the presence of the phases BFO and CFO, for the non-reduced nanocomposites, and for the partially reduced nanocomposites we found three phases BFO, CFO and CF. TEM images showed that these phases are structurally coupled. Isothermal remanent magnetization (IRM) and direct current remanent demagnetization (DCD) measurements were done and the analyzes through the Henkel and δm plots were performed, providing information about the nature of the interactions among the phases and their magnetic behavior. The samples BFO/CFO and BFO/CFO@CF with the lowest percentage of BFO (∼7 wt%) showed exchange coupling between the phases while the other samples exhibited predominantly magnetic dipolar interactions.

Specific Features of Grain Boundaries in Nickel Processed by High-Pressure Torsion

Publications on obtaining bulk nanostructured materials with special properties by various modes of severe plastic deformation, using nickel as an example, are briefly reviewed. Particular attention is paid to the state of grain boundaries, commonly referred to as nonequilibrium, or deformation-modified boundaries, revealed by electron microscopy, including scanning tunneling, Mossbauer spectroscopy, and diffusion studies. It is shown that contribution of specific state of grain boundaries to additional strengthening is often overestimated. In particular, in Ni processed by high pressure torsion, nonequilibrium grain boundaries are formed, which have increased energy and are ultrafast diffusion paths, but they contribute relatively little to the total strengthening.

Promotion effects of alkali metals on iron molybdate catalysts for CO2 catalytic hydrogenation

CO2 hydrogenation is an attractive way to store and utilize carbon dioxide generated by industrial processes, as well as to produce valuable chemicals from renewable and abundant resources. Iron catalysts are commonly used for the hydrogenation of carbon oxides to hydrocarbons. Iron-molybdenum catalysts have found numerous applications in catalysis, but have been never evaluated in the CO2 hydrogenation. In this work, the structural properties of iron-molybdenum catalysts without and with a promoting alkali metal (Li, Na, K, Rb, or Cs) were characterized using X-ray diffraction, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, in-situ 57Fe Mossbauer spectroscopy and operando X-ray adsorption spectroscopy. Their catalytic performance was evaluated in the CO2 hydrogenation. During the reaction conditions, the catalysts undergo the formation of an iron (II) molybdate structure, accompanied by a partial reduction of molybdenum and carbidization of iron. The rate of CO2 conversion and product selectivity strongly depend on the promoting alkali metals, and electronegativity was identified as an important factor affecting the catalytic performance. Higher CO2 conversion rates were observed with the promoters having higher electronegativity, while low electronegativity of alkali metals favors higher light olefin selectivity.

Defect structures and (ferro)magnetism in Zn1-xFexO nanoparticles with the iron concentration level in the dilute regime (x = 0.001 – 0.01) prepared from acetate precursors

Zn1-xFexO nanoparticles with the iron concentrations level in the dilute regime (x = 0.001–––0.01) were produced by a sol–gel route from acetate precursors along with an un-doped and 3 at.% Fe-doped reference. The X-ray diffraction of the un-doped and 0.1–1 at.% Fe-doped samples reveal the reflections for only the ZnO wurtzite structure. Fe doping enhances the a-axis lattice constant, the unit cell volume and the microstrain. Iron doping reduces the average crystallite/particle size (confirmed by Scanning Electron Microscopy), improving the surface-to-volume ratio or the concentration of defective surface sites. XPS identifies the iron in both Fe3+ and Fe2+ states. XPS and 57Fe Mossbauer spectroscopy indicate a broad distribution (distortion) of Fe3+ sites on the surface of ZnO nanoparticles. The blue shift and broadening of the UV emission, and quenching of defect-related photoluminescence in the Fe-doped samples verify the presence of iron in the ZnO lattice and surface intrinsic defects. 0.1–1 at.% Fe-doped ZnO show room temperature ferromagnetism, RTFM, characteristic of dilute magnetic semiconductors, DMS. The magnetization measurements with temperature evidence an antiferromagnetic alignment and an increase of ferromagnetic contribution with Fe doping up to 1 at.%. Zn0.97Fe0.3O reference is a superparamagnetic ZnO/ZnFe2O4 nanocomposite with a blocking temperature of 20 K; HRTEM shows (ultra)fine ZnFe2O4 particles at the surface of ZnO nanoparticles. The analysis of experimental data of 0.1–1 at.% Fe-doped ZnO was done in terms of iron coupling with intrinsic defects, which can generate surface Fe3+ states with geometries similar to the Fe3+ in inverse spinel ZnFe2O4. The superexchange interaction (resembling that in the inverse spinel ZnFe2O4) between the Fe3+ sites with distorted configuration resulting in ferrimagnetism was hypothesised as a possible mechanism of RTFM. Experimental (structural, local chemical, magnetic, optical) and interpretation results can be used to optimize the processing conditions for Fe-doped ZnO to serve as an effective DMS, e.g. for spintronic applications.

Evaluation of Slag Foaming Behavior Using Renewable Carbon Sources in Electric Arc Furnace-Based Steel Production

The influence of different carbon sources, including anthracite, calcined petroleum coke, three samples of high-temperature coke, biochar, and a mixture of 50 wt.% biochar and 50 wt.% coke, on slag foaming behavior was studied. The slag’s composition was set to FeO-CaO-Al2O3-MgO-SiO2, and the temperature for slag foaming was 1600 °C. The effect of the carbon sources was evaluated using foaming characteristics (foam height, foam volume, relative foaming height, and gas fraction), X-ray diffraction (XRD), chemical analysis of the slag foams, Mossbauer spectroscopy, observation by scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) mapping. Different foaming phenomena were found among conventional sources, biochar as a single source, and the mixture of coke and biochar. Biochar showed the most inferior foaming characteristics compared to the other studied carbon sources. Nevertheless, the slag foaming process was improved and showed slag foaming characteristics similar to results obtained using conventional carbon sources when the mixture of 50 wt.% coke and 50 wt.% biochar was used. The XRD analysis revealed a difference between the top and bottom of the slag foams. In almost all cases, a maghemite crystalline phase was detected at the top of the slag foams, indicating oxidation; metallic iron was found at the bottom. Furthermore, a difference in the slag foam (mixture of coke and biochar) was found in the presence of such crystalline phases as magnesium iron oxide (Fe2MgO4) and magnetite (Mg0.4Fe2.96O4). Notwithstanding the carbon source applied, a layer between the foam slag and the crucible wall was found in many samples. Based on the SEM/EDS and XRD results, it was assumed this layer consists of gehlenite (Ca2(Al(AlSi)O7) and two spinels: magnesium aluminate (MgAl2O4) and magnesium iron oxide (Fe2MgO4).

Gamma-resonance method for the diagnosis of leukemia

Background. The modern concept of acute leukemia therapy involves stratification of patients into prognostic risk groups and a differentiated approach to treatment based on prognostic factors. However, antitumor treatment, including cytostatics, targeted agents, immunotherapy, cellular technologies, is not always highly effective, especially in patients with a poor prognosis. The development of new high-tech diagnostic methods and the refinement of leukemia prediction models remain an urgent clinical task.Aim. To demonstrate the fundamental capabilities of the nuclear gamma resonance method in the early diagnosis of leukemia.Materials and methods. The blood of 1 healthy man and 5 patients of different genders and ages with leukemia was examined. Gamma-resonance (Mossbauer) spectra of iron nuclei in their blood were analyzed.Results. Significant differences in the parameters of the spectra of 57Fe nuclei in the blood of both healthy men and patients of different genders and ages were revealed.Conclusion. Nuclear gamma-resonance spectroscopy at the atomic-nuclear level reveals the influence of cancer cells on the state of iron nuclei and, consequently, on the state of blood. This method can be used both for early diagnosis of leukemia and for assessing the population of tumor cells after achieving cytological remission in leukemia.

Exfoliated graphite with γ-Fe2O3 for the removal of oil and organic pollutants from the water surface: Synthesis, Mossbauer study, sorption and magnetic properties

Exfoliated graphite (EG) is a promising sorbent for oil and organic pollutants, which has a high sorption capacity and hydrophobicity. Modifying the EG with ferrimagnetic compound allows EG with sorbed oil to be collected from the water surface with the use of a magnetic field. The aim of this work is to obtain a sorbent based on exfoliated graphite with ferrimagnetic maghemite (γ-Fe2O3) and investigate its structure and functional properties. The preparation of iron-containing EG includes the impregnation of expandable graphite with a FeCl3 water solution and the thermal treatment of impregnated expandable graphite at temperatures between 400 and 1000 °C. Mossbauer spectroscopy, X-ray diffraction analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy show the evolution of the iron-containing phase from FeOCl to the mixture of α-Fe2O3 and γ-Fe2O3, which grants magnetic properties to the samples. EG obtained at 1000 °C has a saturation magnetization of 22.7 emu g−1. High macropore and meso-/micropore volume investigated by mercury porosimetry and nitrogen adsorption-desorption method results in a high sorption rate and sorption capacity of EG up to 30 g g−1 toward oil and liquid hydrocarbons. At the same time, the EG sorption capacity toward water is ten times lower.

Impact of vanadium substitution on structural, magnetic, microwave absorption features and hyperfine interactions of SrCo hexaferrites

The Co-V co-substituted nano Sr-hexaferrite, Sr0.5Co0.5VxFe12−xO19 (0.00 ≤ x ≤ 0.08) (V→SrCo (0.00 ≤ x ≤ 0.08) NHFs), were manufactured by citrate combustion route. The microstructure, morphology, magnetic features, hyperfine interactions and oxidation state and chemical composition of products explained by XRD, SEM with EDX, HR-TEM, VSM, Mossbauer spectrometry, and XPS, respectively. The DXRD (Average crystallite size) of products were assessed via Scherrer formula as within the range of 37 and 83 nm. The hexagonal morphology and chemical composition of the products was presented by TEM, HR-TEM, SEM and EDX analyses. The XPS analysis provided both the composition and oxidation states of prepared NHFs. Mossbauer spectra showed that the s electron density around Fe3+ ions of all sites except 12k influenced V3+ content. The coercivity data indicates that all samples denote a magnetically hard material at both low and high temperatures. Ms, Mr and nB fluctuate with respect to dopant concentration and attain their highest magnitudes for the V→SrCo (x = 0.04) NHFs. A SQR of around 0.5 is achieved at each temperature, reflecting a relatively high large anisotropy field. The field-cooling (FC) curves of all samples yield a drop in magnetization with increasing temperature. Their irreversibility temperature is detected to be beyond 325 K. Both M-H and M-T imply the ferrimagnetic behavior of different samples. Microwave properties were measured between 2 and 18 GHz as S11-S21 parameters. It demonstrated non-linear behavior of the microwave properties vs. V concentration. The origin of the reflection losses in NHVs can be explained by the dipole polarization processes.

Bismuth ferrite-barium titanate system studies around morphotropic phase boundary

Nowadays, the electro-electronic industry and scientific community have a great interest in improving memory devices. A candidate is the bismuth ferrite owing to the coexistence of ferroelectricity and anti-ferromagnetism at room temperature, however, a high leakage current harms their ferroelectric properties. Thus, bismuth ferrite and barium titanate solutions improve the ferroelectric properties of bismuth ferrite and optimize the magnetoelectric coupling factor. This system is called multiferroic, materials exhibit the coexistence of ferromagnetic, ferroelectric, or ferro-elastic orders, which is of interest to the scientific physics community and electronic industry. In this paper, bismuth ferrite-barium titanate system around the morphotropic phase boundary was studied and analyzed. It was observed changes in the structural properties in function of barium titanate content. Calcination temperature was determined from thermogravimetric analysis curves to powders of bismuth ferrite-barium titanate system. Ceramic bodies were densified conventionally. Archimedes’ method was used for density measure. Ceramics with densities greater than 95% were obtained. 93% of the perovskite phase was obtained from structural results. Finally, structural properties were presented and analyzed using Mossbauer spectroscopy as complementary technique. These analyses are very important in solid state physics because to contribute to understanding the phenomenology and synthesis process of multiferroic materials.