Research

13 pages, 6242 KiB

Open AccessEditor’s ChoiceArticle

Improved Energy Storage Density and Efficiency of Nd and Mn Co-Doped Ba_0.7Sr_0.3TiO₃ Ceramic Capacitors Via Defect Dipole Engineering

by Hyunsu Choi, Srinivas Pattipaka, Yong Hoon Son, Young Min Bae, Jung Hwan Park, Chang Kyu Jeong, Han Eol Lee, Sung-Dae Kim, Jungho Ryu and Geon-Tae Hwang

Materials 2023, 16(20), 6753; https://doi.org/10.3390/ma16206753 - 18 Oct 2023

Viewed by 1035

Abstract

In this paper, we investigate the structural, microstructural, dielectric, and energy storage properties of Nd and Mn co-doped Ba_0.7Sr_0.3TiO₃ [(Ba_0.7Sr_0.3)_1−xNd_xTi_1−yMn_yO₃ (BSNTM) ceramics ( [...] Read more.

In this paper, we investigate the structural, microstructural, dielectric, and energy storage properties of Nd and Mn co-doped Ba_0.7Sr_0.3TiO₃ [(Ba_0.7Sr_0.3)_1−xNd_xTi_1−yMn_yO₃ (BSNTM) ceramics (x = 0, 0.005, and y = 0, 0.0025, 0.005, and 0.01)] via a defect dipole engineering method. The complex defect dipoles

{(M n}_{T i}^{”} - V_{O}^{∙ ∙})^{∙}

and

{(M n}_{T i}^{”} - V_{O}^{∙ ∙})

between acceptor ions and oxygen vacancies capture electrons, enhancing the breakdown electric field and energy storage performances. XRD, Raman, spectroscopy, XPS, and microscopic investigations of BSNTM ceramics revealed the formation of a tetragonal phase, oxygen vacancies, and a reduction in grain size with Mn dopant. The BSNTM ceramics with x = 0.005 and y = 0 exhibit a relative dielectric constant of 2058 and a loss tangent of 0.026 at 1 kHz. These values gradually decreased to 1876 and 0.019 for x = 0.005 and y = 0.01 due to the Mn²⁺ ions at the Ti⁴⁺- site, which facilitates the formation of oxygen vacancies, and prevents a decrease in Ti⁴⁺. In addition, the defect dipoles act as a driving force for depolarization to tailor the domain formation energy and domain wall energy, which provides a high difference between the maximum polarization of P_max and remnant polarization of P_r (ΔP = 10.39 µC/cm²). Moreover, the complex defect dipoles with optimum oxygen vacancies in BSNTM ceramics can provide not only a high ΔP but also reduce grain size, which together improve the breakdown strength from 60.4 to 110.6 kV/cm, giving rise to a high energy storage density of 0.41 J/cm³ and high efficiency of 84.6% for x = 0.005 and y = 0.01. These findings demonstrate that defect dipole engineering is an effective method to enhance the energy storage performance of dielectrics for capacitor applications. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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12 pages, 4251 KiB

Open AccessArticle

Advantages of Ferroelectrics as a Component of Heterostructures for Electronic Purposes: A DFT Insight

by Irina Piyanzina, Alexander Evseev, Kirill Evseev, Rinat Mamin, Oleg Nedopekin, Dmitrii Tayurskii and Viktor Kabanov

Materials 2023, 16(20), 6672; https://doi.org/10.3390/ma16206672 - 13 Oct 2023

Viewed by 713

Abstract

The main advantage of using ferroelectric materials as a component of complex heterostructures is the ability to tune various properties of the whole system by means of an external electric field. In particular, the electric field may change the polarization direction within the [...] Read more.

The main advantage of using ferroelectric materials as a component of complex heterostructures is the ability to tune various properties of the whole system by means of an external electric field. In particular, the electric field may change the polarization direction within the ferroelectric material and consequently affect the structural properties, which in turn affects the electronic and magnetic properties of the neighboring material. In addition, ferroelectrics allow the electrostriction phenomenon to proceed, which is promising and can be used to affect the magnetic states of the interface state in the heterostructure through a magnetic component. The interfacial phenomena are of great interest, as they provide extended functionality useful for next-generation electronic devices. Following the idea of utilizing ferroelectrics in heterostructural components in the present works, we consider 2DEG, the Rashba effect, the effect of magnetoelectric coupling, and magnetostriction in order to emphasize the advantages of such heterostructures as components of devices. For this purpose, model systems of LaMnO

_{3}

/BaTiO

_{3}

, La

_{2}

CuO

_{4}

/BaTiO

_{3}

, Bi/BaTiO

_{3}

, and Bi/PbTiO

_{3}

, Fe/BaTiO

_{3}

heterostructures are investigated using density functional theory calculations. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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12 pages, 2179 KiB

Open AccessEditor’s ChoiceArticle

Anisotropic Properties of Epitaxial Ferroelectric Lead-Free 0.5[Ba(Ti_0.8Zr_0.2)O₃]-0.5(Ba_0.7Ca_0.3)TiO₃ Films

by Nicholas Cucciniello, Alessandro R. Mazza, Pinku Roy, Sundar Kunwar, Di Zhang, Henry Y. Feng, Katrina Arsky, Aiping Chen and Quanxi Jia

Materials 2023, 16(20), 6671; https://doi.org/10.3390/ma16206671 - 13 Oct 2023

Viewed by 889

Abstract

As the energy demand is expected to double over the next 30 years, there has been a major initiative towards advancing the technology of both energy harvesting and storage for renewable energy. In this work, we explore a subset class of dielectrics for [...] Read more.

As the energy demand is expected to double over the next 30 years, there has been a major initiative towards advancing the technology of both energy harvesting and storage for renewable energy. In this work, we explore a subset class of dielectrics for energy storage since ferroelectrics offer a unique combination of characteristics needed for energy storage devices. We investigate ferroelectric lead-free 0.5[Ba(Ti_0.8Zr_0.2)O₃]-0.5(Ba_0.7Ca_0.3)TiO₃ epitaxial thin films with different crystallographic orientations grown by pulsed laser deposition. We focus our attention on the influence of the crystallographic orientation on the microstructure, ferroelectric, and dielectric properties. Our results indicate an enhancement of the polarization and strong anisotropy in the dielectric response for the (001)-oriented film. The enhanced ferroelectric, energy storage, and dielectric properties of the (001)-oriented film is explained by the coexistence of orthorhombic-tetragonal phase, where the disordered local structure is in its free energy minimum. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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12 pages, 17002 KiB

Open AccessEditor’s ChoiceArticle

Influence of Lattice Mismatch on Structural and Functional Properties of Epitaxial Ba_0.7Sr_0.3TiO₃ Thin Films

by Jonas Wawra, Kornelius Nielsch and Ruben Hühne

Materials 2023, 16(17), 6036; https://doi.org/10.3390/ma16176036 - 02 Sep 2023

Viewed by 778

Abstract

Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba

_{0.7}

Sr [...] Read more.

Substrate-induced strains can significantly influence the structural properties of epitaxial thin films. In ferroelectrics, this might lead to significant changes in the functional properties due to the strong electromechanical coupling in those materials. To study this in more detail, epitaxial Ba

_{0.7}

Sr

_{0.3}

TiO

_{3}

films, which have a perovskite structure and a structural phase transition close to room temperature, were grown with different thicknesses on REScO

_{3}

(RE–rare earth element) substrates having a smaller lattice mismatch compared to SrTiO

_{3}

. A fully strained SrRuO

_{3}

bottom electrode and Pt top contacts were used to achieve a capacitor-like architecture. Different X-ray diffraction techniques were applied to study the microstructure of the films. Epitaxial films with a higher crystalline quality were obtained on scandates in comparison to SrTiO

_{3}

, whereas the strain state of the functional layer was strongly dependent on the chosen substrate and the thickness. Differences in permittivity and a non-linear polarization behavior were observed at higher temperatures, suggesting that ferroelectricity is supressed under tensile strain conditions in contrast to compressive strain for our measurement configuration, while a similar reentrant relaxor-like behavior was found in all studied layers below 0

° C

. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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23 pages, 11660 KiB

Open AccessArticle

Structural, Magnetic, and Magneto-Optical Properties of Thin Films of BaM Hexaferrite Grown by Laser Molecular Beam Epitaxy

by Boris Krichevtsov, Alexander Korovin, Sergey Suturin, Aleksandr A. Levin, Ivan Lobov, Andrey Telegin, Andrey Badalyan, Vladimir Sakharov, Igor Serenkov, Maxim Dorogov and Nikolai Sokolov

Materials 2023, 16(12), 4417; https://doi.org/10.3390/ma16124417 - 15 Jun 2023

Viewed by 872

Abstract

Thin films of BaM hexaferrite (BaFe₁₂O₁₉) were grown on α-Al₂O₃(0001) substrates by laser molecular beam epitaxy. Structural, magnetic, and magneto-optical properties were studied using medium-energy ion scattering, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray [...] Read more.

Thin films of BaM hexaferrite (BaFe₁₂O₁₉) were grown on α-Al₂O₃(0001) substrates by laser molecular beam epitaxy. Structural, magnetic, and magneto-optical properties were studied using medium-energy ion scattering, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray diffraction, magneto-optical spectroscopy, and magnetometric techniques, and the dynamics of magnetization by ferromagnetic resonance method. It was shown that even a short time annealing drastically changes the structural and magnetic properties of films. Only annealed films demonstrate magnetic hysteresis loops in PMOKE and VSM experiments. The shape of hysteresis loops depends on thickness of films showing practically rectangular loops and high value of remnant magnetization (M_r/M_s~99%) for thin films (50 nm) and much broader and sloped loops in thick (350–500 nm) films. The magnitude of magnetization 4πM_s ≈ 4.3 kG in thin films corresponds to that in bulk BaM hexaferrite. Photon energy and sign of bands in magneto-optical spectra of thin films correspond to ones observed earlier in bulk samples and films of BaM hexaferrite. FMR spectra of 50 nm films at 50 GHz consist of a number of narrow lines. The width of main line ΔH~20 Oe is lower than has been reported up to now. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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18 pages, 5933 KiB

Open AccessArticle

Magnetic Charge Model for Leakage Signals from Surface Defects in Ferromagnetic Material

by Xinyu Li, Guangming Sheng, Zimin Meng, Fan Qin and Zhifeng Liu

Materials 2023, 16(10), 3750; https://doi.org/10.3390/ma16103750 - 15 May 2023

Viewed by 804

Abstract

A novel three-dimensional theoretical model of magnetic flux leakage (MFL) is proposed in this paper based on the magnetic dipole model. The magnetic dipole model assumes that a ferromagnetic specimen with defects is exposed to a uniform external magnetic field that causes a [...] Read more.

A novel three-dimensional theoretical model of magnetic flux leakage (MFL) is proposed in this paper based on the magnetic dipole model. The magnetic dipole model assumes that a ferromagnetic specimen with defects is exposed to a uniform external magnetic field that causes a uniform magnetization around the defect surface. Under this assumption, the MFL can be regarded as arising from magnetic charges on the defect surface. Previous theoretical models were mostly used to analyze simple crack defects such as cylindrical and rectangular cracks. In this paper, we developed a magnetic dipole model for more complex defect shapes such as circular truncated holes, conical holes, elliptical holes, and double-curve-shaped crack holes to complement the existing defect shapes. Experimental results and comparisons with previous models demonstrate that the proposed model provides a better approximation of complex defect shapes. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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18 pages, 16757 KiB

Open AccessArticle

Relationship between the Synthesis Method and the Magnetoelectric Properties of Bismuth Sodium-Potassium Titanate/Nickel Cobalt Ferrite Lead-Free Composites

by Javier Camargo, Leandro Ramajo and Miriam Castro

Materials 2023, 16(7), 2759; https://doi.org/10.3390/ma16072759 - 30 Mar 2023

Viewed by 1088

Abstract

In this work, the influence of the synthesis methods of piezoelectric and magnetostrictive phases on the final properties of the Bi_0.5(Na_0.8K_0.2)_0.5TiO₃-Ni_0.5Co_0.5Fe₂O₄ composites was studied. Different routes [...] Read more.

In this work, the influence of the synthesis methods of piezoelectric and magnetostrictive phases on the final properties of the Bi_0.5(Na_0.8K_0.2)_0.5TiO₃-Ni_0.5Co_0.5Fe₂O₄ composites was studied. Different routes were used to individually synthesize each phase, and the composites were prepared using different fractions for each phase. Composites were sintered, and the structural, microstructural, dielectric, and magnetoelectric properties were evaluated. According to the selected synthesis method employed for each phase, different particle sizes and reactivities of the individual phases were obtained. These differences determined the suitable sintering temperature for each set of composites and were responsible for the final properties. In fact, magnetoelectric properties were modulated by the combination of composition and synthesis routes. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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11 pages, 1531 KiB

Open AccessArticle

Nonlinear Optical Properties in an Epitaxial YbFe₂O₄ Film Probed by Second Harmonic and Terahertz Generation

by Hongwu Yu, Yoichi Okimoto, Atsuya Morita, Shuhei Shimanuki, Kou Takubo, Tadahiko Ishikawa, Shin-ya Koshihara, Ryusei Minakami, Hirotake Itoh, Shinichiro Iwai, Naoshi Ikeda, Takumi Sakagami, Mayu Nozaki and Tatsuo Fujii

Materials 2023, 16(5), 1989; https://doi.org/10.3390/ma16051989 - 28 Feb 2023

Cited by 1 | Viewed by 1559

Abstract

An epitaxial film of YbFe₂O₄, a candidate for oxide electronic ferroelectrics, was fabricated on yttrium-stabilized zirconia (YSZ) substrate by magnetron sputtering technique. For the film, second harmonic generation (SHG), and a terahertz radiation signal were observed at room temperature, [...] Read more.

An epitaxial film of YbFe₂O₄, a candidate for oxide electronic ferroelectrics, was fabricated on yttrium-stabilized zirconia (YSZ) substrate by magnetron sputtering technique. For the film, second harmonic generation (SHG), and a terahertz radiation signal were observed at room temperature, confirming a polar structure of the film. The azimuth angle dependence of SHG shows four leaves-like profiles and is almost identical to that in a bulk single crystal. Based on tensor analyses of the SHG profiles, we could reveal the polarization structure and the relationship between the film structure of YbFe₂O₄ and the crystal axes of the YSZ substrate. The observed terahertz pulse showed anisotropic polarization dependence consistent with the SHG measurement, and the intensity of the emitted terahertz pulse reached about 9.2% of that emitted from ZnTe, a typical nonlinear crystal, implying that YbFe₂O₄ can be applied as a terahertz wave generator in which the direction of the electric field can be easily switched. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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15 pages, 4913 KiB

Open AccessEditor’s ChoiceArticle

Effect of Poling on Multicatalytic Performance of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Sr_0.3)TiO₃ Ferroelectric Ceramic for Dye Degradation

by Akshay Gaur, Shivam Dubey, Zainab Mufarreh Elqahtani, Samia ben Ahmed, Mohammed Sultan Abdulghaffar Al-Buriahi, Rahul Vaish and Vishal Singh Chauhan

Materials 2022, 15(22), 8217; https://doi.org/10.3390/ma15228217 - 18 Nov 2022

Cited by 19 | Viewed by 1752

Abstract

Ferroelectric materials with a spontaneous polarization are proven to be potential multicatalysts in water remediation applications. The composition of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Sr_0.3)TiO₃ (BST-BZT) was examined for photocatalysis, piezocatalysis, and piezo-photocatalysis processes by degrading an [...] Read more.

Ferroelectric materials with a spontaneous polarization are proven to be potential multicatalysts in water remediation applications. The composition of 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Sr_0.3)TiO₃ (BST-BZT) was examined for photocatalysis, piezocatalysis, and piezo-photocatalysis processes by degrading an azo dye named methylene blue (MB). Generally, dis-aligned dipoles restrict the catalytic activities due to which the BST-BZT powder sample was poled by the corona poling technique. Coupled piezocatalysis and photocatalysis process, i.e., the piezo-photocatalysis process has shown maximum dye degradation. There was a significant improvement in degradation efficiency by using a poled BST-BZT sample compared to the unpoled sample in all processes, thus the results suggest an extensive scope of poled ferroelectric ceramic powder in the catalysis field. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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12 pages, 2210 KiB

Open AccessEditor’s ChoiceArticle

Antiferromagnet–Ferromagnet Transition in Fe_1−xCu_xNbO₄

by Diego S. Evaristo, Raí F. Jucá, João M. Soares, Rodolfo B. Silva, Gilberto D. Saraiva, Robert S. Matos, Nilson S. Ferreira, Marco Salerno and Marcelo A. Macêdo

Materials 2022, 15(21), 7424; https://doi.org/10.3390/ma15217424 - 22 Oct 2022

Viewed by 1157

Abstract

Iron niobates, pure and substituted with copper (Fe_1−xCu_xNbO₄ with x = 0–0.15), were prepared by the solid-state method and characterized by X-ray diffraction, Raman spectroscopy, and magnetic measurements. The results of the structural characterizations revealed the high solubility [...] Read more.

Iron niobates, pure and substituted with copper (Fe_1−xCu_xNbO₄ with x = 0–0.15), were prepared by the solid-state method and characterized by X-ray diffraction, Raman spectroscopy, and magnetic measurements. The results of the structural characterizations revealed the high solubility of Cu ions in the structure and better structural stability compared to the pure sample. The analysis of the magnetic properties showed that the antiferromagnetic–ferromagnetic transition was caused by the insertion of Cu²⁺ ions into the FeNbO₄ structure. The pure FeNbO₄ structure presented an antiferromagnetic ordering state, with a Néel temperature of approximately 36.81K. The increase in substitution promoted a change in the magnetic ordering, with the state passing to a weak ferromagnetic order with a transition temperature (T_c) higher than the ambient temperature. The origin of the ferromagnetic ordering could be attributed to the increase in super-exchange interactions between Fe/Cu ions in the Cu²⁺-O-Fe³⁺ chains and the formation of bound magnetic polarons in the oxygen vacancies. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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12 pages, 2741 KiB

Open AccessArticle

Stress Evaluation of Welded Joints with Metal Magnetic Memory Testing Based on Tension–Compression Fatigue Test

by Huipeng Wang, Zhiwei Xu, Dongwei Cai, Lihong Dong, Guozheng Ma, Haidou Wang and Bin Liu

Materials 2022, 15(9), 3103; https://doi.org/10.3390/ma15093103 - 25 Apr 2022

Cited by 1 | Viewed by 1409

Abstract

Metal magnetic memory testing (MMMT) is an effective nondestructive technique for fatigue damage monitoring of weldments because of its capacity for stress evaluation. An experimental investigation of the effect of the applied fatigue stress on MMMT signals, including the tangential component B_x [...] Read more.

Metal magnetic memory testing (MMMT) is an effective nondestructive technique for fatigue damage monitoring of weldments because of its capacity for stress evaluation. An experimental investigation of the effect of the applied fatigue stress on MMMT signals, including the tangential component B_x and the normal component B_z, during tension–compression fatigue tests in welded joints was carried out systematically. The B_x and B_z signals at different fatigue cycles and fatigue stresses were collected and analyzed, and the results showed that there was a peak of B_x and abnormal peaks of B_z that existed at the welded joint before loading. After loading, the peak of B_x and the abnormal peaks of B_z reversed, and the B_x signals moved upward and the B_z signals rotated anticlockwise dramatically in the first few fatigue cycles. After the fatigue cycle number was larger than 1000, B_x and B_z were stable, with very little fluctuation. In addition, the characteristics of B_x signals, the mean value, and the peak value of the average of B_x had an extremely significant linear relationship with the applied fatigue stress during the stable stage of the fatigue test, which indicates that MMMT is a feasible method for fatigue stress evaluation and even residual fatigue life estimation for weldments in service. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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10 pages, 2191 KiB

Open AccessArticle

Switching Diagram of Core-Shell FePt/Fe Nanocomposites for Bit Patterned Media

by Yuhui Wang, Ying Zheng, Ziyi Zhong, Zijun Wang, Yongfeng Liang and Pingping Wu

Materials 2022, 15(7), 2581; https://doi.org/10.3390/ma15072581 - 31 Mar 2022

Cited by 2 | Viewed by 1233

Abstract

In the current work, a core-shell type exchange coupled composite structure was constructed by micromagnetic simulation with a phase FePt core and an iron shell. Four types of switching loops with magnetic domain structure evolution were demonstrated. Based on the simulation results, a [...] Read more.

In the current work, a core-shell type exchange coupled composite structure was constructed by micromagnetic simulation with a phase FePt core and an iron shell. Four types of switching loops with magnetic domain structure evolution were demonstrated. Based on the simulation results, a switching type diagram was constructed, which displays various hysteresis loops as a function of core radius and shell thickness. Furthermore, the effects of switching type and composite structure on the coercivity and remanent magnetization were predicted and discussed. This finding indicates that core-shell type FePt/Fe composite structure film has a large advantage in designing exchange-coupled bit patterned media to realize high-density storage devices at the nanoscale. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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10 pages, 3010 KiB

Open AccessArticle

Investigation of Phase Transitions in Ferromagnetic Nanofilms on a Non-Magnetic Substrate by Computer Simulation

by Sergey V. Belim

Materials 2022, 15(7), 2390; https://doi.org/10.3390/ma15072390 - 24 Mar 2022

Cited by 1 | Viewed by 1330

Abstract

Magnetic properties of ferromagnetic nanofilms on non-magnetic substrate are examined by computer simulation. The substrate influence is modeled using the two-dimensional Frenkel-Kontorova potential. The film has a cubic crystal lattice. Cases of different ratio for substrate period and ferromagnetic film period are considered. [...] Read more.

Magnetic properties of ferromagnetic nanofilms on non-magnetic substrate are examined by computer simulation. The substrate influence is modeled using the two-dimensional Frenkel-Kontorova potential. The film has a cubic crystal lattice. Cases of different ratio for substrate period and ferromagnetic film period are considered. The difference in film and substrate periods results in film deformations. These deformations result in a change in the magnetic properties of the film. The Ising model and the Metropolis algorithm are used for the study of magnetic properties. The dependence of Curie temperature on film thickness and substrate potential parameters is calculated. Cases of different values for the coverage factor are considered. The deformation of the film layers is reduced away from the substrate when it is compressed or stretched. The Curie temperature increases when the substrate is compressed and decreases when the substrate is stretched. This pattern is performed for films with different thicknesses. If the coating coefficient for the film is different from one, periodic structures with an increased or reduced concentration of atoms are formed in the film first layer. These structures are absent in higher layers. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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11 pages, 35271 KiB

Open AccessEditor’s ChoiceArticle

Grain Growth Behavior and Electrical Properties of 0.96(K_0.46−xNa_0.54−x)Nb_0.95Sb_0.05O₃–0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ Ceramics

by Yeon-Ju Park, Il-Ryeol Yoo, Seong-Hui Choi, Jiung Cho and Kyung-Hoon Cho

Materials 2022, 15(7), 2357; https://doi.org/10.3390/ma15072357 - 22 Mar 2022

Cited by 1 | Viewed by 1362

Abstract

This study investigated the causes of microstructural changes and the resultant electrical properties according to the sintering temperature of 0.96(K_0.46−xNa_0.54−x)Nb_0.95Sb_0.05O₃-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ lead-free ceramics by analyzing [...] Read more.

This study investigated the causes of microstructural changes and the resultant electrical properties according to the sintering temperature of 0.96(K_0.46−xNa_0.54−x)Nb_0.95Sb_0.05O₃-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ lead-free ceramics by analyzing the correlation between vacancy concentrations and 2D nucleation. When sintered for 4 h, no grain growth occurred for the x = 0.000 composition over a wide temperature range, demonstrating that the existence of initial vacancies is essential for grain growth. As x increased, that is, as the vacancy concentration increased, the critical driving force (ΔG_C) for 2D nucleation decreased, and abnormal grain growth was promoted. The number and size of these abnormal grains increased as the sintering temperature increased, but at sintering temperatures above 1100 °C, they decreased again owing to a large drop in ΔG_C. The x = 0.005 specimen sintered at 1085 °C exhibited excellent piezoelectric properties of d₃₃ = 498 pC/N and k_p = 0.45 due to the large number of large abnormal grains with an 83% tetragonal phase fraction. The x = 0.000 specimen sintered at 1130 °C with suppressed grain growth exhibited good energy storage properties because of its very high relative density and small grain size of 300 to 400 nm. Full article

(This article belongs to the Special Issue Ferromagnetic and Ferroelectric Materials: Synthesis, Applications, and Techniques)

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