Effect of Cu Substitution and Heat Treatment on Phase Formation and Magnetic Properties of Sm12Co88−xCux Melt-Spun Ribbons

The phase structure and microstructure of Sm₁₂Co_88−xCu_x (x = 0, 2, 4, 6, 8, 10; at.%) as-cast alloys and melt-spun ribbons prepared via the arc-melting method and melt-spun technology were studied experimentally by X-ray diffraction (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results reveal that the Sm₁₂Co_88−xCu_x (x = 0) as-cast alloy contains Sm₂Co₁₇ and Sm₅Co₁₉ phases, while the Sm₁₂Co_88−xCu_x (x = 2) as-cast alloy is composed of Sm₂Co₁₇, Sm₂Co₇ and Sm(Co, Cu)₅ phases. Sm₂Co₁₇ and Sm(Co, Cu)₅ phases are detected in Sm₁₂Co_88−xCu_x (x = 4, 6, 8, 10) as-cast alloys. Meanwhile, Sm₁₂Co_88−xCu_x ribbons show a single SmCo₇ phase, which is still formed in the ribbons annealed at 1023 K for one hour. After annealed at 1123 K for two hours, cooled slowly down to 673 K at 0.5 K/min and then kept for four hours, the ribbons are composed of Sm₂Co₁₇ and Sm(Co, Cu)₅ phases. The magnetic measurements of Sm₁₂Co_88−xCu_x ribbons were performed by vibrating sample magnetometer (VSM). The results exhibit that the maximum magnetic energy product ((BH)_max), the coercivity (H_cj) and the remanence (B_r) of the Sm₁₂Co_88−xCu_x ribbons increase generally with the increase in Cu substitution. In particular, the magnetic properties of the ribbons annealed at 1123 K and 673 K increase significantly with the increase in Cu substitution, resulting from the increase in the volume fraction of the formed Sm(Co, Cu)₅ phase after heat treatment.     

Impact of A-Site Cation Deficiency on Charge Transport in La0.5−xSr0.5FeO3−δ

The electrical conductivity of La_0.5−xSr_0.5FeO_3−δ, investigated as a function of the nominal cation deficiency in the A-sublattice, x, varying from 0 to 0.02, has demonstrated a nonlinear dependence. An increase in the x value from 0 to 0.01 resulted in a considerable increase in electrical conductivity, which was shown to be attributed mainly to an increase in the mobility of the charge carriers. A combined analysis of the defect equilibrium and the charge transport in La_0.5−xSr_0.5FeO_3−δ revealed the increase in the mobility of oxygen ions, electrons, and holes by factors of ~1.5, 1.3, and 1.7, respectively. The observed effect is assumed to be conditioned by a variation in the oxide structure under the action of the cationic vacancy formation. It was found that the cation deficiency limit in La_0.5−xSr_0.5FeO_3−δ did not exceed 0.01. A small overstep of this limit was shown to result in the formation of (Sr,La)Fe₁₂O₁₉ impurity, which even in undetectable amounts reduced the conductivity of the material. The presence of (Sr,La)Fe₁₂O₁₉ impurity was revealed by X-ray diffraction on the ceramic surface after heat treatment at 1300 °C. It is most likely that the formation of traces of the liquid phase under these conditions is responsible for the impurity migration to the ceramic surface. The introduction of a cation deficiency of 0.01 into the A-sublattice of La_0.5−xSr_0.5FeO_3−δ can be recommended as an effective means to enhance both the oxygen ion and the electron conductivity and improve ceramic sinterability.     

Effects of the Addition of Co or Ni Atoms on Structure and Magnetism of FeB Amorphous Alloy: Ab Initio Molecular Dynamics Simulation

The effects of the substitution of Fe by Co or Ni on both the structure and the magnetic properties of FeB amorphous alloy were investigated using first-principle molecular dynamics. The pair distribution function, Voronoi polyhedra, and density of states of Fe_80−xTM_xB₂₀ (x = 0, 10, 20, 30, and 40 at.%, TM(Transition Metal): Co, Ni) amorphous alloys were calculated. The results show that with the increase in Co content, the saturation magnetization of Fe_80−xCo_xB₂₀ (x = 0, 10, 20, 30, and 40 at.%) amorphous alloys initially increases and then decreases upon reaching the maximum at x = 10 at.%, while for Fe_80−xNi_xB₂₀ (x = 0, 10, 20, 30, and 40 at.%), the saturation magnetization decreases monotonously with the increase in Ni content. Accordingly, for the two kinds of amorphous alloys, the obtained simulation results on the variation trends of the saturation magnetization with the change in alloy composition are in good agreement with the experimental observation. Furthermore, the relative maximum magnetic moment was recorded for Fe₇₀Co₁₀B₂₀ amorphous alloy, due to the induced increased magnetic moments of the Fe atoms surrounding the Co atom in the case of low Co dopant, as well as the increase in the exchange splitting energy caused by the enhancement of local atomic symmetry.     

The Effects of La Doping on the Crystal Structure and Magnetic Properties of Ni2In-Type MnCoGe1−xLax (x = 0, 0.01, 0.03) Alloys

In this experiment, a series of MnCoGe_1−xLa_x (x = 0, 0.01, 0.03) alloy samples were prepared using a vacuum arc melting method. The crystal structure and magnetic properties of alloys were investigated using X-ray diffraction (XRD), Rietveld method, physical property measurement system (PPMS), and vibrating sample magnetometer (VSM) analyses. The results show that all samples were of high-temperature Ni₂In-type phases, belonging to space group P6₃/mmc (194) after 1373 K annealing. The results of Rietveld refinement revealed that the lattice constant and the volume of MnCoGe_1−xLa_x increased along with the values of La constants. The magnetic measurement results show that the Curie temperatures (T_C) of the MnCoGe_1−xLa_x series alloys were 294, 281, and 278 K, respectively. The maximum magnetic entropy changes at 1.5T were 1.64, 1.53, and 1.56 J·kg⁻¹·K⁻¹, respectively. The respective refrigeration capacities (RC) were 60.68, 59.28, and 57.72J·kg⁻¹, with a slight decrease along the series. The experimental results show that the doping of La results in decreased T_C, basically unchanged magnetic entropy, and slightly decreased RC.     

Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Manganites La(0.7−x)EuxBa0.3MnO3

Here, we report synthesis and investigations of bulk and nano-sized La_(0.7−x)Eu_xBa_0.3MnO₃ (x ≤ 0.4) compounds. The study presents a comparison between the structural and magnetic properties of the nano- and polycrystalline manganites La_(0.7−x)Eu_xBa_0.3MnO₃, which are potential magnetocaloric materials to be used in domestic magnetic refrigeration close to room temperature. The parent compound, La_0.7Ba_0.3MnO₃, has Curie temperature T_C = 340 K. The magnetocaloric effect is at its maximum around T_C. To reduce this temperature below 300 K, we partially replaced the La ions with Eu ions. A solid-state reaction was used to prepare bulk polycrystalline materials, and a sol-gel method was used for the nanoparticles. X-ray diffraction was used for the structural characterization of the compounds. Transmission electron spectroscopy (TEM) evidenced nanoparticle sizes in the range of 40–80 nm. Iodometry and inductively coupled plasma optical emission spectrometry (ICP-OES) was used to investigate the oxygen content of the studied compounds. Critical exponents were calculated for all samples, with bulk samples being governed by tricritical mean field model and nanocrystalline samples governed by the 3D Heisenberg model. The bulk sample with x = 0.05 shows room temperature phase transition T_C = 297 K, which decreases with increasing x for the other samples. All nano-sized compounds show lower T_C values compared to the same bulk samples. The magnetocaloric effect in bulk samples revealed a greater magnetic entropy change in a relatively narrow temperature range, while nanoparticles show lower values, but in a temperature range several times larger. The relative cooling power for bulk and nano-sized samples exhibit approximately equal values for the same substitution level, and this fact can substantially contribute to applications in magnetic refrigeration near room temperature. By combining the magnetic properties of the nano- and polycrystalline manganites, better magnetocaloric materials can be obtained.     

Microstructure and Magnetocaloric Effect by Doping C in La-Fe-Si Ribbons

The melt-spun ribbons of LaFe_11.5Si_1.5C_x (x = 0, 0.1, 0.2, 0.3) compounds are prepared by the melt fast-quenching method. The doping of C is beneficial to the nucleation and precipitation of the La (Fe, Si)₁₃ phase, which is indicated by the microstructure observation and the elemental analysis. Subsequently, the ribbons of LaFe_11.5Si_1.5C_0.2 are annealed at different times, and the phase composition, the microstructures, and the magnetic properties are investigated. The LaFe_11.5Si_1.5C_0.2 ribbons annealed at 1273 K for 2 h achieved the best magnetic properties, and the maximum isothermal magnetic entropy change with a value of 9.45 J/(kg·K) upon an applied field of 1.5 T at an increased Curie temperature 255 K.     

Compositional Dependence of Curie Temperature and Magnetic Entropy Change in the Amorphous Tb–Co Ribbons

The Curie temperature (T_c) and magnetic entropy change (−ΔS_m), and their relationship to the alloy composition of Tb–Co metallic glasses, were studied systematically in this paper. It was found that, in contrast to the situation in amorphous Gd–Co ribbons, the dependence of Tc on Tb content and the maximum −ΔS_m vs. T_c -2/3 plots in Tb–Co binary amorphous alloys do not follow a linear relationship, both of which are supposed to be closely related to the non-linear compositional dependence of Tb–Co interaction due to the existence of orbital momentum in Tb.     

Effect of Gd3+ Substitution on Thermoelectric Power Factor of Paramagnetic Co2+-Doped Calcium Molybdato-Tungstates

A series of Co²⁺-doped and Gd³⁺-co-doped calcium molybdato-tungstates, i.e., Ca_1−3x−yCo_{y x}Gd_2x(MoO₄)_1−3x(WO₄)_3x (CCGMWO), where 0 < x ≤ 0.2, y = 0.02 and represents vacancy, were successfully synthesized by high-temperature solid-state reaction method. XRD studies and diffuse reflectance UV–vis spectral analysis confirmed the formation of single, tetragonal scheelite-type phases with space group I4₁/a and a direct optical band gap above 3.5 eV. Magnetic and electrical measurements showed insulating behavior with n-type residual electrical conductivity, an almost perfect paramagnetic state with weak short-range ferromagnetic interactions, as well as an increase of spin contribution to the magnetic moment and an increase in the power factor with increasing gadolinium ions in the sample. Broadband dielectric spectroscopy measurements and dielectric analysis in the frequency representation showed a relatively high value of dielectric permittivity at low frequencies, characteristic of a space charge polarization and small values of both permittivity and loss tangent at higher frequencies.     

The Effect of Cobalt-Sublattice Disorder on Spin Polarisation in Co2FexMn1?xSi Heusler Alloys

In this work we present a theoretical study of the effect of disorder on spin polarisation at the Fermi level, and the disorder formation energies for Co₂Fe_xMn_1−xSi (CFMS) alloys. The electronic calculations are based on density functional theory with a Hubbard U term. Chemical disorders studied consist of swapping Co with Fe/Mn and Co with Si; in all cases we found these are detrimental for spin polarisation, i.e., the spin polarisation not only decreases in magnitude, but also can change sign depending on the particular disorder. Formation energy calculation shows that Co–Si disorder has higher energies of formation in CFMS compared to Co₂MnSi and Co₂FeSi, with maximum values occurring for x in the range 0.5–0.75. Cross-sectional structural studies of reference Co₂MnSi, Co₂Fe_0.5Mn_0.5Si, and Co₂FeSi by Z-contrast scanning transmission electron microscopy are in qualitative agreement with total energy calculations of the disordered structures.     

Magnetic Properties of the Ferromagnetic Shape Memory Alloys Ni50+xMn27?xGa23 in Magnetic Fields

Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloys Ni_50+xMn_27−xGa₂₃ (x = 2.0, 2.5, 2.7) were performed. For x = 2.7, in which the martensite transition and the ferromagnetic transition occur at the same temperature, the martensite transition starting temperature T_Ms shift in magnetic fields around a zero magnetic field was estimated to be dT_Ms/dB = 1.1 ± 0.2 K/T, thus indicating that magnetic fields influences martensite transition. We discussed the itinerant electron magnetism of x = 2.0 and 2.5. As for x = 2.5, the M⁴ vs. B/M plot crosses the origin of the coordinate axis at the Curie temperature, and the plot indicates a good linear relation behavior around the Curie temperature. The result is in agreement with the theory by Takahashi, concerning itinerant electron ferromagnets.     

Boost the Crystal Installation and Magnetic Features of Cobalt Ferrite/M-Type Strontium Ferrite Nanocomposites Double Substituted by La3+ and Sm3+ Ions (2CoFe2O4/SrFe12−2xSmxLaxO19)

Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉; x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La³⁺–Sm³⁺ double substitution on the formation, structure, and magnetic properties of CoFe₂O₄/SrFe_12−2xSm_xLa_xO₁₉ nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe³⁺ ion by Sm³–⁺La³⁺ions promoted the formation of pure 2CoFe₂O₄/SrFe₁₂O₁₉ nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm³⁺–La³⁺ substitution at ≤1100 °C. In addition, samples with an Sm³⁺–La³⁺ ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La₃Co₃O₈; dominant phase) and samarium ferrite (SmFeO₃). The crystallite size range at all constituent phases was in the nanocrystalline range, from 39.4 nm to 122.4 nm. The average crystallite size of SrFe₁₂O₁₉ phase increased with the number of Sm³⁺–La³⁺ substitutions, whereas that of CoFe₂O₄ phase decreased with an x of up to 0.5. La–Sm co-doped ion substitution increased the saturation magnetization (Ms) value and the subrogated ratio to 0.2, and the Ms value decreased with the increasing number of double substitutions. A high saturation magnetization value (Ms = 69.6 emu/g) was obtained using a La³⁺–Sm³⁺ co-doped ratio of 0.2 at 1200 for 2 h, and a high coercive force value (Hc = 1192.0 Oe) was acquired using the same ratio at 1000 °C.     

Large Low-Field Reversible Magnetocaloric Effect in Itinerant-Electron Hf1−xTaxFe2 Alloys

First-order isostructural magnetoelastic transition with large magnetization difference and controllable thermal hysteresis are highly desirable in the development of high-performance magnetocaloric materials used for energy-efficient and environmental-friendly magnetic refrigeration. Here, we demonstrate large magnetocaloric effect covering the temperature range from 325 K to 245 K in Laves phase Hf_1−xTa_xFe₂ (x = 0.13, 0.14, 0.15, 0.16) alloys undergoing the magnetoelastic transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state on decreasing the temperature. It is shown that with the increase of Ta content, the nature of AFM to FM transition is gradually changed from second-order to first-order. Based on the direct measurements, large reversible adiabatic temperature change (ΔT_ad) values of 2.7 K and 3.4 K have been achieved under a low magnetic field change of 1.5 T in the Hf_0.85Ta_0.15Fe₂ and Hf_0.84Ta_0.16Fe₂ alloys with the first-order magnetoelastic transition, respectively. Such remarkable magnetocaloric response is attributed to the rather low thermal hysteresis upon the transition as these two alloys are close to intermediate composition point of second-order transition converting to first-order transition.     

Structural,Magnetic, Dielectric and Piezoelectric Properties of Multiferroic PbTi1−xFexO3−δ Ceramics

PbTi_1−xFe_xO_3−δ (x = 0, 0.3, 0.5, and 0.7) ceramics were prepared using the classical solid-state reaction method. The investigated system presented properties that were derived from composition, microstructure, and oxygen deficiency. The phase investigations indicated that all of the samples were well crystallized, and the formation of a cubic structure with small traces of impurities was promoted, in addition to a tetragonal structure, as Fe³⁺ concentration increased. The scanning electron microscopy (SEM) images for PbTi_1−xFe_xO_3−δ ceramics revealed microstructures that were inhomogeneous with an intergranular porosity. The dielectric permittivity increased systematically with Fe³⁺ concentration, increasing up to x = 0.7. A complex impedance analysis revealed the presence of multiple semicircles in the spectra, demonstrating a local electrical inhomogeneity due the different microstructures and amounts of oxygen vacancies distributed within the sample. The increase of the substitution with Fe³⁺ ions onto Ti⁴⁺ sites led to the improvement of the magnetic properties due to the gradual increase in the interactions between Fe³⁺ ions, which were mediated by the presence of oxygen vacancies. The PbTi_1−xFe_xO_3−δ became a multifunctional system with reasonable dielectric, piezoelectric, and magnetic characteristics, making it suitable for application in magnetoelectric devices.     

Theoretical Prediction and Experimental Validation of the Glass-Forming Ability and Magnetic Properties of Fe-Si-B Metallic Glasses from Atomic Structures

Developing new soft magnetic amorphous alloys with a low cost and high saturation magnetization (B_s) in a simple alloy system has attracted substantial attention for industrialization and commercialization. Herein, the glass-forming ability (GFA), thermodynamic properties, soft magnetic properties, and atomic structures of Fe_80+xSi_5−xB₁₅ (x = 0–4) amorphous soft magnetic alloys were investigated by ab initio molecular dynamics (AIMD) simulations and experiments. The pair distribution function (PDF), Voronoi polyhedron (VP), coordination number (CN), and chemical short- range order (CSRO) were analyzed based on the AIMD simulations for elucidating the correlations between the atomic structures with the glass-forming ability and magnetic properties. For the studied compositions, the Fe₈₂Si₃B₁₅ amorphous alloy was found to exhibit the strongest solute–solute avoidance effect, the longest Fe-Fe bond, a relatively high partial CN for the Fe-Fe pair, and the most pronounced tendency to form more stable clusters. The simulation results indicated that Fe₈₂Si₃B₁₅ was the optimum composition balancing the saturation magnetization and the GFA. This prediction was confirmed by experimental observations. The presented work provides a reference for synthesizing new Fe-Si-B magnetic amorphous alloys.     

Magnetic and Magneto-Caloric Properties of the Amorphous Fe92−xZr8Bx Ribbons

Magnetic and magnetocaloric properties of the amorphous Fe_92−xZr₈B_x ribbons were studied in this work. Fully amorphous Fe₈₉Zr₈B₃, Fe₈₈Zr₈B₄, and Fe₈₇Zr₈B₅ ribbons were fabricated. The Curie temperature (T_c), saturation magnetization (M_s), and the maximum entropy change with the variation of a magnetic field (−ΔS_m^peak) of the glassy ribbons were significantly improved by the boron addition. The mechanism for the enhanced T_c and −ΔS_m^peak by boron addition was studied.     

Microstructural Design of Ba0.5La0.5Co0.5Fe0.5O3 Perovskite Ceramics

Ba_0.5La_0.5Co_0.5Fe_0.5O_3−δ was synthesized in the solid-state reaction route. The influence of ball milling parameters (such as milling media size, angular velocity, and time), pelletizing pressure, and annealing parameters on the microstructure was studied. The grain size distribution and density or specific surface area changes were investigated in each approach while the individual parameters were changed. The evaluation of BLCF synthesis parameters enables tailoring the microstructure to various applications. It was observed that with lowering the size of milling balls and increasing the angular velocity the material will be porous and thus more appropriate as electrode material in proton ceramic fuel cell or electrolyzer. An increase of time, balls diameter, and/or angular velocity of milling enables one to densify the material in case of membrane application in, e.g., as a gas sensor. The significant influence on densification has also annealing temperature increase. Applying 1200 °C during annealing leads to dense material, while at 1100 °C shows visible porosity of the product. In this work, we present the results of the BLCF synthesis parameters change allowing the selection of appropriate parameter values depending on the further application as PCCs.     

Influence of Cu Content on Structure,Thermal Stability and Magnetic Properties in Fe72−xNi8Nb4CuxSi2B14 Alloys

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe_72−xNi₈Nb₄Cu_xSi₂B₁₄ alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔG^amorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔG^mix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures T_x1onset and T_x1 of the alpha-iron phase together with the activation energy E_a for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P_10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P_10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P_10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P_10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 10⁴ Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).     

Influence of Dissolving Fe–Nb–B–Dy Alloys in Zirconium on Phase Structure,Microstructure and Magnetic Properties

This paper refers to the structural and magnetic properties of [(Fe₈₀Nb₆B₁₄)_0.88Dy_0.12]_1−xZr_x (x = 0; 0.01; 0.02; 0.05; 0.1; 0.2; 0.3; 0.5) alloys obtained by the vacuum mold suction casting method. The analysis of the phase contribution indicated a change in the compositions of the alloys. For x < 0.05, occurrence of the dominant Dy₂Fe₁₄B phase was observed, while a further increase in the Zr content led to the increasing contribution of the Fe–Zr compounds and, simultaneously, separation of crystalline Dy. The dilution of (Fe₈₀Nb₆B₁₄)_0.88Dy_0.12 in Zr strongly influenced the magnetization processes of the examined alloys. Generally, with the increasing x parameter, we observed a decrease in coercivity; however, the unexpected increase in magnetic saturation and remanence for x = 0.2 and x = 0.3 was shown and discussed.     

The Effect of Niobium Doping on the Electrical Properties of 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 Lead-Free Piezoelectric Ceramics

Ceramics in the system (Bi_0.5K_0.5)TiO₃-BiFeO₃ have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO₃-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium (Nb) is carried out to reduce the conductivity of (Bi_0.5K_0.5)TiO₃-BiFeO₃. Powders of composition 0.4(K_0.5Bi_0.5)Ti_1−xNb_xO₃-0.6BiFe_1−xNb_xO₃ (x = 0, 0.01 and 0.03) are prepared by the mixed oxide method and sintered at 1050 °C for 1 h. The effect of Nb doping on the structure is examined by X-ray diffraction. The microstructure is examined by scanning electron microscopy. The variation in relative permittivity with temperature is measured using an impedance analyzer. Ferroelectric properties are measured at room temperature using a Sawyer Tower circuit. Piezoelectric properties are measured using a d₃₃ meter and a contact type displacement sensor. All the samples have high density, a rhombohedral unit cell and equiaxed, micron-sized grains. All the samples show relaxor-like behavior. Nb doping causes a reduction in conductivity by one to two orders of magnitude at 200 °C. The samples have narrow P-E loops reminiscent of a linear dielectric. The samples all possess bipolar butterfly S-E loops characteristic of a classic ferroelectric material. Nb doping causes a decrease in d₃₃ and S_max/E_max.     

Investigation of Mechanical and Magnetic Properties of Co-Based Amorphous Powders Obtained by Atomization

Properties of Co-based alloys with high Glass Forming Ability (GFA) in the form of powder are still not widely known. However, powders of high GFA alloys are often used for the development of bulk metallic glasses by additive manufacturing. In this work Co_47.6B_21.9Fe_20.4Si_5.1Nb₅% at. and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁% at. were developed by gas-atomization. Obtained powders in size 50–80 µm were annealed at T_g and T_x of each alloy. Then SEM observation, EDS analyses, differential thermal analysis, X-ray diffraction, nanoindentation, Mössbauer, and magnetic properties research was carried out for as-atomized and annealed states. The gas atomization method proved to be an efficient method for manufacturing Co-based metallic glasses. The obtained powder particles were spherical and chemically homogeneous. Annealing resulted in an increase of mechanical properties such as hardness and the elastic module of Co_47.6B_21.9Fe_20.4Si_5.1Nb₅% at and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁%, which was caused by crystallization. The magnetic study shows that Co_47.6B_21.9Fe_20.4Si_5.1Nb₅ and Co₄₂B_26.5Fe₂₀Ta_5.5Si₅Cu₁ are soft magnetic and semi-hard magnetic materials, respectively.