Ferrite Ceramics Research Articles

Investigation on impedance spectroscopy and transport properties of co-doped bismuth ferrite ceramics

Investigation on impedance spectroscopy and transport properties of co-doped bismuth ferrite ceramics

Evolution of ferroelectric and piezoelectric properties of BiFeO3 ceramics doped with lanthanum and zirconium

In this study, we performed cation substitutions at Bi-site (La3+) and Fe-site (Zr4+) to investigate their possible benefit for the ferroelectric properties of BiFeO3 ceramics. The cations with higher valence (Zr4+) ought to suppress the formation of structural defects during syntheses, such as oxygen vacancies and Fe2+. These defects are responsible for high leakage currents and low breakdown voltages characteristic of the pure BiFeO3. However, doping only with Zr did not improve the ferroelectric properties of bismuth ferrite. These samples were unable to persist electric fields above 30 kV/cm. On the other hand, the increase in lanthanum concentration resulted in improved ferroelectric and piezoelectric properties of the samples, sustaining electric fields above 100 kV/cm. Among the investigated samples, the highest remnant polarization of 24 μC/cm2 and piezoelectric coefficient (d33) of 34 pC/N reached Bi0.85La0.15FeO3 sample at 160 kV/cm. The share of non-ferroelectric contribution to the total polarization of this sample was the lowest (∼ 11 %). When it comes to the co-doped samples, the addition of Zr transformed the behavior from leaky ferroelectric to predominantly leaky dielectric. It indicated that doping with La significantly improved the ferroelectric properties of bismuth ferrite ceramics. In contrast, even a low Zr concentration of 1 mol% could outbalance the influence of much larger La concentrations (10 and 15 mol%).

Structural and electromagnetic properties of 3D printed and electron beam sintered lithium ferrite ceramic

In this work, the structures and electromagnetic properties of lithium ferrite ceramics manufactured by the additive method, based on the extrusion deposition of ferrite samples with a binder and their subsequent heating with high-energy electron beam, were studied. Preliminary synthesis of ferrite powder was carried out by a solid-phase method using iron oxide and lithium carbonate. To prepare ferrite paste, a binder based on ethylcellulose and terpineol was used. The printed samples were sintered by heating with 1.4 MeV electron beam using an ELV-6 accelerator. Using X-ray phase analysis, it was established that the sintered ceramic consists mainly of an ordered α−Li0.5Fe2.5O4 phase and a certain amount of disordered β−Li0.5Fe2.5O4 phase. Ferrite ceramics are characterized by a relative density of 72.6–92.1%, specific saturation magnetization of 63–65 emu/g, Curie temperature of 628–630 °C, electrical resistivity of 108–106 Ω cm, depending on the thickness of the printed sample (200 and 400 μm) and sintering temperature (1100 and 1200 °С).

Improved gyromagnetic properties of LiZnTi ferrites co-fired with Bi2O3-La2O3 additives at low temperature

In this work, low temperature-sintered Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites mixed with x wt.% (x = 0.00–0.30 wt%) of La2O3 and 1.5 wt% of Bi2O3 were successfully prepared by the solid-state reaction method. The variations in phase composition, microstructure, and gyromagnetic properties of the as-prepared samples were studied in detail. XRD patterns and refinement results show that La2O3 didn't affect the formation of the spinel phase, but a small amount of La3+ might enter into the lattice structure. The micro-morphological analysis and grain size statistics demonstrate that the addition of La2O3 significantly suppressed the grain growth, and the average grain size decreased from 2.19 μm (x = 0.00 wt%) to 1.14 μm (x = 0.15 wt%). The uniformity of the grain size distribution was improved, and the degree of densification was significantly increased. Meanwhile, the saturation magnetization (4πMs) increased from 3921 Gs to 3989 Gs, the coercivity (Hc) decreased from 457.5 A/m to 312.5 A/m, and the ferromagnetic resonance linewidth (ΔH) decreased from 328.5 Oe to 220.7 Oe. Our study indicates that the Bi2O3-La2O3 mixture is an effective sintering additive for low-temperature sintering of LiZnTi ferrite ceramics, which will play an important role in the development of low-temperature co-fired ferrites.

Optimization of structural, optical, dielectric and magnetic properties of Gd3+ substituted Mg-Mn mixed spinel ferrite ceramics

Manganese magnesium ferrite (Mg0.5Mn0.5Fe2O4) and Gd doped Mg0.5Mn0.5Fe2O4 (Mg0.5Mn0.5Fe2-xGdxO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized using the solid-state method. The structural study was performed using the powder X-ray diffraction (XRD) technique. The XRD plot confirms the presence of a spinel cubic structure for pure MgMn ferrite and the existence of a secondary GdFeO3 phase in addition to the cubic spinel phase for Gd-doped MgMn ferrite. The average crystallite size estimated from the Williamson-Hall plot decreases from 42.75 nm to 18.97 nm with the increase in Gd content. The microstructural study confirms the clear grains with well-defined grain boundaries. The Fourier Transform Infrared (FTIR) spectra of the samples show the vibrational bands at 3440 cm−1, 1636 cm−1, 1385 cm−1, 1100 cm−1, and 560 cm−1 assigned to tetrahedral and octahedral sites. The improvement in dielectric property has been observed for Gd-doped samples. The saturation magnetization and remnant magnetization decrease from 0.7 to 0.3 emu and 0.035 to 0.0273 emu respectively. The coercivity increases from 31 to 75 Oe with the increase in Gd content. The fabricated spinel ferrites have significant electrical and magnetic properties which may be promising candidates for microwave devices.

Study on liquid-phase sintering and magnetic properties of SLA-printed Mn-Zn ferrite ceramics

To obtain Mn-Zn ferrite magnetic ceramic parts with good densification and magnetic properties, a study was conducted. Mn-Zn ferrite magnetic ceramic parts with a solid particle content of 58 vol% were prepared using stereolithography (SLA). The SLA-cured ceramic blanks were degreased and sintered. The degreasing process for Mn-Zn ferrite parts was optimized using a direct heat degreasing method, resulting in a suitable process for the ferrite magnetic ceramic paste system. The method of liquid phase sintering is proposed for sintering the degreased ferrite parts. The study investigated the impact of the content of accelerant, sintering temperature, and holding time on the density and magnetic properties of Mn-Zn ferrite parts. The optimal parameters were found to be a firing aid content of 3 wt%, a sintering temperature of 900 °C, and a holding time of 90 min. Under these conditions, the parts exhibited a density of 4.43 g/cm3, densification of 91.4 %, saturation magnetization strength of 64 emu/g, and coercivity of 10 Oe. Finally, the sintering control mechanism of SLA-printed ferrite magnetic ceramics was analyzed. The study revealed the grain growth process and magnetization principle of Mn-Zn ferrite during liquid phase sintering. This research provides guidance for the subsequent photocuring printing and degreasing sintering of Mn-Zn ferrite ceramics. Additionally, Mn-Zn ferrite magnetic ceramic parts prepared by the SLA method also hold a wide application prospect in various precision electronic components.

Enhanced magnetic, ferroelectric, and photocatalytic properties of Nd and Co doped bismuth ferrite (Bi1−xNdxFe1−yCoyO3) ceramics

This study investigates the structural, magnetic, ferroelectric, and photocatalytic properties of bismuth ferrite ceramics co-doped with Nd and Co. The ceramics were synthesized using a combination of solid-state and mechanical milling techniques, and their compositions were varied within the range of Bi1−xNdxFe1−yCoyO3, with x and y ranging from 0.05 to 0.20. The materials were characterized using XRD (Rietveld refinement), WDXRF, Raman spectroscopy, and impedance analysis. Magnetic measurements revealed that the saturation magnetization (Ms) and remanent magnetization (Mr) significantly increased as the concentrations of Nd and Co increased. The magnetic properties showed an improvement, with the Ms value increasing from 8.12 emu/g for x = y = 0.05 to 18.67 emu/g for x = y = 0.20. Similarly, the magnetic response increased from 1.49 emu/g to 5.63 emu/g. The ferroelectric properties also exhibited improvement, with polarization values increasing from 0.79 µC/cm2 to 2.02 µC/cm2 at a frequency of 50 Hz. Photocatalytic activity was evaluated by measuring the degradation of organic dyes under visible light exposure, which showed a notable increase of up to 70 % when the doping concentrations were at their highest. These results suggest that Bi1−xNdxFe1−yCoyO3 ceramics have a wide range of applications, making them promising materials for advanced devices and environmental cleanup. By doping with Nd and Co, the materials’ properties are enhanced, leading to significant improvements in their ability to convert light into energy.

Study of Dielectric Relaxation Dynamics and Transport Properties of Nd3+-Substituted Bismuth Ferrite Ceramics for Energy Storage Applications

Study of Dielectric Relaxation Dynamics and Transport Properties of Nd³⁺-Substituted Bismuth Ferrite Ceramics for Energy Storage Applications

Influence of sintering temperature on structural, electrical, dielectric, and magnetic properties of magnesium ferrite (MgFe2O4) ceramics prepared using powder derived via Sol-Gel auto-combustion

Influence of sintering temperature on structural, electrical, dielectric, and magnetic properties of magnesium ferrite (MgFe2O4) ceramics prepared using powder derived via Sol-Gel auto-combustion

Microstructures and magnetic properties of NiCuZn ferrite ceramics doped with MnO2–Bi2O3

Microstructures and magnetic properties of NiCuZn ferrite ceramics doped with MnO2–Bi2O3

Effect of Sm2O3 additive on the microstructure, magnetic and electrical properties of LiTiZn ferrite ceramics

LiTiZn ferrites were prepared by a conventional two-steps solid sintering method. According to X-ray diffraction (XRD) results, the primary phase of all specimens was ferrite spinel. It is shown that Sm2O3 additive 1 wt% slightly reduces the lattice parameter of the spinel phase and leads to the appearance of an additional phase SmFeO3. For the first time for LiTiZn ferrite received, that Sm2O3 additive leads to significant increase of the electrical resistivity and the Curie temperature by 25°. Thus, the problem with dielectric loss reduction in the microwave and thermal stability increasing of ferrite ceramics was solved. At the same time, there is a 6 % decrease in saturation magnetization and 11 % in density while coercive force increases by the 60 %. In addition, scanning electron microscope (SEM) data show significant influence of Sm2O3 additive on grain morphology. The energy dispersive spectroscopy (EDS) patterns confirm SmFeO3 phase formation. The results of the study can be used for improvement of sintering ferrite products in a factory.

Control of sintering characteristics and gyromagnetic properties of LiZn-based microwave ferrite ceramics by Nb2O5 doping

In this study, a new strategy of trace amounts of Nb2O5 doping was employed to control microwave loss of Ti-Mn-Bi co-substituted LiZn-based ferrite ceramics sintered at 890 °C. The results revealed the distribution of doped Nb in the spinel ferrites. Partial Nb5+ ions entered the lattices and induced the generation of Fe2+ ions, resulting in a decrease in the magnetocrystalline anisotropy linewidth (ΔHa). The rest of Nb2O5 remained at grain boundaries and formed high resistance layers, which contributed to lowering the dielectric loss (tanδε). Due to the particular distribution of Nb, a dual-structure and higher densification were observed, and thus the porosity-induced line broadening contributions (ΔHp) was reduced. Notably, by doping with 0.15 wt.% Nb2O5, the LiZn-based ferrites presented excellent magnetic properties (ΔH = 87 Oe, tanδε = 3.24 × 10-4, 4πMs = 3799 Gauss, Br/Bs = 0.9), which shows promising potential for low-loss microwave ferrite devices.

Cold sintering process for densification of Fe3O4 ceramic magnets with improved properties

Iron oxide-based ferrite ceramics, widely applied in high-frequency applications, are conventionally produced through high-temperature sintering processes, often resulting in grain growth and phase transformation. In this study, we used a cold sintering process (CSP) with oxalic acid (OA) as a solvent to consolidate iron oxide (Fe3O4) ceramics at a low temperature of 160 °C. The OA-assisted CSP technique has demonstrated a remarkable capacity to facilitate the dissolution and redeposition of iron oxide ions, leading to the interconnection of Fe3O4 particles, forming densely packed ceramics even at low-temperature sintering. Importantly, CSP maintained particle sizes and hindered phase transitions of Fe3O4. The OA concentrations in CSP had a minimal impact on crystal structure and magnetic properties, but it significantly enhanced microstructural features, density, hardness, and electrical resistance. Compared to reference samples prepared without an aqueous solution or with water alone, the CSP-prepared Fe3O4 ceramics with OA exhibited substantially improved density (a relative density of ∼80 %), mechanical properties (Vickers hardness of 3.5–4.0 GPa), magnetic properties (saturation magnetization >70 emu/g), and electrical resistance (electrical conductivity ∼10−3 S/cm at 102–106 Hz). These findings demonstrate a novel approach to fabricating Fe3O4 ceramics at significantly lower temperatures while still achieving properties comparable to those sintered at high temperatures.

Влияние механической обработки исходных реагентов на структурные и электрические свойства LiFeO2 керамики

This work investigates the effect of mechanical treatment of initial Fe2O3 and Li2CO3 powders on the structure and electrical properties of lithium ferrite ceramics of the chemical composition LiFeO2. Mechanical treatment was carried out in an AGO-2S ball mill for 60 minutes at a bowl rotation speed of 2220 rpm. Sintering of ceramic samples was carried out in a laboratory furnace at 1050 °C for 1 hour. Using X-ray phase analysis data, it was shown that the introduction of the mechanical treatment of powders leads to a decrease in the concentration of the α-LiFeO2 phase in ferrite ceramics from 97,9 to 93,9 wt.%, as well as an increase in the secondary LiFe5O8 phase from 2,1 to 6,1 wt.%. In this case, during sintering, a more homogeneous and finely porous structure of the samples was formed. Based on the temperature dependences of the electrical conductivity of the samples, it was established that changes in electrical resistance are associated both with the microstructure and with the processes of adsorption-desorption (depending on temperature) of gas from the surrounding atmosphere into ferrite ceramics. The ferrite ceramics obtained by mechanical treatment is of interest for its further use as an adsorption material for carbon oxides.

Investigation of the dielectric and optoelectronic properties of Nd3+-substituted bismuth ferrite ceramics in THz/far-infrared region

Investigation of the dielectric and optoelectronic properties of Nd3+-substituted bismuth ferrite ceramics in THz/far-infrared region

Effect of Pr and Mn co-substitution on Structural and Optical Properties of Bismuth Ferrite

One of the most recent developments in the area of modern optics arises due to perovskite materials. The ABO3 perovskite materials like bismuth ferrite is an appealing alternative for various optical devices. Hence, in the present study, Praseodymium (Pr) and Manganese (Mn) co-substituted bismuth ferrite ceramics are prepared by the modified sol-gel method and the correlation between structural and optical properties with the variation in co-substitution concentration has been investigated. Rietveld refinement of X-ray diffraction patterns demonstrates a structural phase change in crystal symmetry from rhombohedral to orthorhombic phase with the increase in concentration for x ≥ 0.025. Lattice deformation in the co-substituted samples is confirmed by Fourier Transform Infrared (FTIR) and Raman spectra. UV–vis diffuse reflectance spectra confirm the strong absorption of light in the visible region. Furthermore, optical energy band gap decreases from 1.95 eV to 1.50 eV with increase in concentration from x = 0.000 to x = 0.100. The refractive index attains the maximum value i.e. 6.16 for x = 0.025 whereas it drops to minimum value of 4.06 for x = 0.100. This demonstrates that the structural modification in bismuth ferrite can be used to tune its optical parameters for the device applications.

Lowered ferromagnetic resonance linewidth and enhanced spin wave linewidth of nickel-based ferrite ceramics using hot-pressing method

Previous investigations commonly employed solid-state sintering to fabricate Ni-based ferrite ceramics to improve magnetic performance. A few researchers used the hot-pressing method to prepare Ni-based ferrites, but their porosity remained relatively high values (>2%), resulting in high ferromagnetic resonance line widths (ΔH). To date, the influence of high-temperature and high-pressure forming processes on ΔH and spin wave line width (ΔHk) in Ni-based ferrite ceramics has been rarely reported using hot pressing. This study utilized a uniaxial hot-pressing method and systematically investigated the effect of porosity, grain size and grain uniformity on the magnetic properties of Ni-based ferrite ceramics. Porosity played a crucial role in determining ΔH at different sintering temperatures. As the sintering temperature increased, the reduced porosity resulted in a decrease in ΔH. Under varying sintering pressures, the grain uniformity primarily affected ΔH. Increasing pressures led to more uniform grains, causing a decrease in ΔH. The ΔHk was directly associated with the grain sizes. With the increase of sintering temperatures, the grain sizes increased, leading to a decrease in ΔHk. Conversely, as the pressure increased, the decreased grain sizes brought the increased ΔHk. Compared to other hot-pressing results on the Ni-based ferrite ceramics, the optimized high-temperature and high-pressure processing with annealing significantly reduced the porosity of Ni-based ferrite ceramics (0.11%). In comparison with the solid-state sintering without pressures, the optimized hot-pressed Ni-based ferrite ceramics exhibited a 7% increase in saturation magnetization, a 63% reduction in ΔH and a 6.5% increase in ΔHk. The striking reduction of ΔH suggests that microwave devices assembled from Ni-based ferrite ceramics could withstand high power levels while minimizing lower electromagnetic losses, predicting promising applications for Ni-based ferrite materials in high-power microwave ferrite devices.

An alternative approach to obtaining low coercivity ZnMn ferrite ceramics with the use of solution combustion method: effect of sintering conditions on structural, morphological and magnetic parameters

An alternative approach to obtaining low coercivity ZnMn ferrite ceramics with the use of solution combustion method: effect of sintering conditions on structural, morphological and magnetic parameters

Effects of Bi2O3–CuO additives on microstructure and microwave properties of low-temperature-sintered NiCuZn ferrite ceramics

In this study, (Ni0.2Cu0.2Zn0.6O)1.03(Fe2O3)0.97 ferrite ceramics with low microwave loss were synthesized through low-temperature sintering and doped with low eutectic mixture Bi2O3–CuO. Additionally, the influence of Bi2O3–CuO doping amount on phase composition, microstructure, and microwave performance of NiCuZn ferrite ceramics was systematically explored. It was found that all samples exhibited pure spinel phase. Moreover, scanning electron microscopy analysis revealed that appropriate doping amount of the Bi2O3–CuO mixture promoted grain growth and densification, leading to dense dual microstructure in NiCuZn ferrite ceramics. Notably, this microstructure significantly enhanced microwave properties of the material. For Bi2O3–CuO doping amount of 0.5 wt % and at sintering temperature of 910 °C, the NiCuZn ferrite ceramics exhibited low ferromagnetic resonance linewidth (ΔH ≈ 90 Oe), minimal dielectric loss (tanδε ≈ 2.73 × 10−4) at 9.3 GHz, and high saturation magnetization (4πMs ≈ 3644 Gauss). These results highlight the potential of Bi2O3–CuO as promising sintering aid, which could support the application of NiCuZn ferrite ceramics to microwave devices.

Investigation and treatment of carbon pollution in LiZn ferrite ceramics prepared by spark plasma sintering

In this study, lithium–zinc ferrite (LZF) ceramics were prepared by spark plasma sintering. Problem of carbon pollution was effectively resolved by annealing decarburization, formation of BN-coated carbon paper, and formation of protective layer of different metal foils (Ti, Mo, W, and Ta). The effects of carbon pollution and different protective layers on microstructure and dielectric and magnetic properties of LZF ceramics were studied comprehensively. Results reveal that annealing decarburization and BN-coated carbon paper could significantly improve resistance and saturation magnetization (Ms) of LZF, while real part of dielectric constant (ε′) and dielectric loss (tanδ) were significantly reduced. X-ray diffraction patterns indicate that all selected protective layers can provide good spinel-phase LZF ceramics. The utilization of metallic foil as protective layer can effectively reduce carburization, improve the resistance of LZF ceramics, and reduce ε′ and tanδ values. X-ray photoemission spectroscopy and Raman spectroscopy results reveal that cations with the highest valence state replace Fe3+ at B-site. The use of metal foil protective layer leads to the infiltration of metal ions into LZF lattice, leading to the increase in the lattice constant and decrease in the Ms value. This study deepens the understanding of carburization during SPS, providing a reference scheme for future applications.