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Keywords = BNT–BT

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14 pages, 6801 KiB  
Article
Effect of Zr Doping on BNT–5BT Lead-Free Ceramics: Substitutional and Excess Incorporation Analysis
by Mauro Difeo, Miriam Castro and Leandro Ramajo
Micro 2025, 5(3), 35; https://doi.org/10.3390/micro5030035 - 28 Jul 2025
Viewed by 126
Abstract
This study evaluates the effect of zirconium (Zr) incorporation on the structural, microstructural, and functional properties of lead-free ceramics based on the 0.95(Bi0.5Na0.5)TiO3–0.05BaTiO3 (BNT–5BT) system. Two distinct doping strategies were investigated: (i) the substitutional incorporation of [...] Read more.
This study evaluates the effect of zirconium (Zr) incorporation on the structural, microstructural, and functional properties of lead-free ceramics based on the 0.95(Bi0.5Na0.5)TiO3–0.05BaTiO3 (BNT–5BT) system. Two distinct doping strategies were investigated: (i) the substitutional incorporation of Zr4+ at the Ti4+ site (BNT–5BT–xZrsub), and (ii) the addition of ZrO2 in excess (BNT–5BT–xZrexc). The samples were synthesized via conventional solid-state reaction and characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM/EDS), and electrical measurements, including dielectric, ferroelectric, and piezoelectric responses. Both doping routes were found to influence phase stability and electromechanical performance. Substitutional doping notably reduced the coercive field while preserving high remanent polarization, resulting in an enhanced piezoelectric coefficient (d33). These results highlight the potential of Zr-modified BNT–5BT ceramics for lead-free energy harvesting applications. Full article
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11 pages, 1806 KiB  
Article
Enhanced Electrical Property and Thermal Stability in Lead-Free BNT–BT–BF Ceramics
by Kangle Zhou, Enxiang Hou, Yanfeng Qu, Yan Mu and Junjun Wang
Ceramics 2025, 8(2), 70; https://doi.org/10.3390/ceramics8020070 - 7 Jun 2025
Viewed by 985
Abstract
The synergistic combination of outstanding electrical properties and exceptional thermal stability holds significant implications for advancing piezoelectric ceramic applications. In this work, lead-free ((1−x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBiFeO3 (x = 0.08, 0.10, 0.12)) ceramics were synthesized using a [...] Read more.
The synergistic combination of outstanding electrical properties and exceptional thermal stability holds significant implications for advancing piezoelectric ceramic applications. In this work, lead-free ((1−x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBiFeO3 (x = 0.08, 0.10, 0.12)) ceramics were synthesized using a conventional solid-state method, with systematic investigation of phase evolution, microstructural characteristics, and their coupled effects on electromechanical performance and thermal stability. Rietveld refinement analysis revealed a rhombohedral–tetragonal (R–T) phase coexistence, where the tetragonal phase fraction maximized at x = 0.10. This structural optimization enabled the simultaneous enhancement of piezoelectricity and thermal resilience. The x = 0.10 composition achieved recorded values of d33 = 132 pC/N, g33 = 26.11 × 10−3 Vm/N, and a depolarization temperature Td = 105 °C. These findings establish BiFeO3 doping as a dual-functional strategy for developing high-performance lead-free ceramics. Full article
(This article belongs to the Special Issue Advances in Electronic Ceramics, 2nd Edition)
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11 pages, 7570 KiB  
Article
Enhancing the Energy Storage Properties and Breakdown Strength of Lead-Free Bismuth-Sodium Titanate-Based Ceramics Through NaNbO3 Doping
by Jingxia Gao, Haizhou Guo, Hongxia Li, Hui Li, Liqin Yue, Rui Wang, Jiangyan Si, Qiaoqiao Zhao and Yangyang Zhang
Crystals 2025, 15(3), 287; https://doi.org/10.3390/cryst15030287 - 20 Mar 2025
Viewed by 596
Abstract
Dielectric capacitors with a high density of recoverable energy storage are extremely desirable for a variety of uses. However, these capacitors often exhibit lower breakdown strengths and energy efficiency compared to other materials, which poses significant challenges for their practical use. We report [...] Read more.
Dielectric capacitors with a high density of recoverable energy storage are extremely desirable for a variety of uses. However, these capacitors often exhibit lower breakdown strengths and energy efficiency compared to other materials, which poses significant challenges for their practical use. We report on a novel antiferroelectric ceramic system in the present study, (1 − x){0.97[0.985(0.93Bi0.5Na0.5TiO3–0.07BaTiO3)–0.015Er)]–0.03AlN}–xNaNbO3 (x = 0, 10 wt%, 20 wt%, 30 wt%, and 40 wt%), synthesized via a conventional solid-state reaction approach. Here, (Bi0.5Na0.5TiO3–BaTiO3) is denoted as BNT–BT. We observed that varying the NaNbO3 (NN) content gradually refined the grain size of the ceramics, narrowed their hysteresis loops, and transformed their phase structure from antiferroelectric to relaxor ferroelectric. These changes enhanced breakdown strength (Eb), thus increasing the performance of energy storage. Specifically, the recoverable energy density (Wrec) and energy storage efficiency ), respectively, reached 0.67–1.06 J/cm3 and 44–88% at electric fields of 110–155 kV/cm, with the highest performance observed at 30 wt% NN doping. Additionally, over a broad range of temperature and frequency, the 70 wt% {0.97[0.985(BNT–BT)–0.015Er]–0.03AlN}–30 wt% NN ceramic demonstrated exceptional stability in energy storage. These results demonstrate the significant potential of lead-free(1 − x)({0.97[0.985(BNT–BT)–0.015Er]–0.03AlN}–xNN ceramics for the applications of high-performance energy storage. Full article
(This article belongs to the Section Materials for Energy Applications)
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26 pages, 7707 KiB  
Review
Textured Lead-Free Piezoelectric Ceramics: A Review of Template Effects
by Temesgen Tadeyos Zate, Cenk Abdurrahmanoglu, Vincenzo Esposito and Astri Bjørnetun Haugen
Materials 2025, 18(3), 477; https://doi.org/10.3390/ma18030477 - 21 Jan 2025
Cited by 4 | Viewed by 1718
Abstract
Crystallographic texture engineering through templated grain growth (TGG) has gained prominence as a highly effective strategy for optimizing the electromechanical performance of lead-free piezoelectric ceramics, offering a pathway toward sustainable alternatives to lead-based systems like lead zirconate titanate (PZT). By achieving high degrees [...] Read more.
Crystallographic texture engineering through templated grain growth (TGG) has gained prominence as a highly effective strategy for optimizing the electromechanical performance of lead-free piezoelectric ceramics, offering a pathway toward sustainable alternatives to lead-based systems like lead zirconate titanate (PZT). By achieving high degrees of texture, with Lotgering factors (LFs) often exceeding 90%, these systems have demonstrated piezoelectric properties that rival or even surpass their lead-based counterparts. Despite these advancements, the field lacks a comprehensive understanding of how specific template parameters influence the texture quality and functional properties across different material systems. This review provides an in-depth analysis of the influence of the template morphology, composition, and crystallographic orientation on the texturing of key lead-free systems, including BaTiO3 (BT), (K0.5Na0.5)NbO3 (KNN), and Bi0.5Na0.5TiO3 (BNT). Furthermore, it explores how the template selection affects the induced crystallographic direction, and how this impacts the material’s phase structure and domain configurations, ultimately influencing the piezoelectric and dielectric properties. By consolidating the existing knowledge and identifying current challenges, this work highlights key strategies for optimizing the texture and electromechanical performance in lead-free ceramics, providing essential insights for future research aimed at advancing high-performance, environmentally friendly piezoelectric materials for applications such as sensors, actuators, and energy-harvesting devices. Full article
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12 pages, 4379 KiB  
Article
Improving the Energy Storage Performance in Bi0.5Na0.5TiO3-Based Ceramics by Combining Relaxor and Antiferroelectric Properties
by Srinivas Pattipaka, Yeseul Lim, Yundong Jeong, Mahesh Peddigari, Yuho Min, Jae Won Jeong, Jongmoon Jang, Sung-Dae Kim and Geon-Tae Hwang
Materials 2024, 17(20), 5044; https://doi.org/10.3390/ma17205044 - 15 Oct 2024
Viewed by 1371
Abstract
Ceramic capacitors have received great attention for use in pulse power systems owing to their ultra-fast charge–discharge rate, good temperature stability, and excellent fatigue resistance. However, the low energy storage density and low breakdown strength (BDS) of ceramic capacitors limit the practical applications [...] Read more.
Ceramic capacitors have received great attention for use in pulse power systems owing to their ultra-fast charge–discharge rate, good temperature stability, and excellent fatigue resistance. However, the low energy storage density and low breakdown strength (BDS) of ceramic capacitors limit the practical applications of energy storage technologies. In this work, we present a series of relaxor ferroelectric ceramics (1−x) [0.94 Bi0.5Na0.5TiO3 –0.06BaTiO3]– x Sr0.7Bi0.2TiO3 (1-x BNT-BT- x SBT; x = 0, 0.20, 0.225, 0.25, 0.275 and 0.30) with improved energy storage performances by combining relaxor and antiferroelectric properties. XRD, Raman spectra, and SEM characterizations of BNT-BT-SBT ceramics revealed a rhombohedral–tetragonal phase, highly dynamic polar nanoregions, and a reduction in grain size with a homogeneous and dense microstructure, respectively. A high dielectric constant of 1654 at 1 kHz and low remnant polarization of 1.39 µC/cm2 were obtained with the addition of SBT for x = 0.275; these are beneficial for improving energy storage performance. The diffuse phase transition of these ceramics displays relaxor behavior, which is improved with SBT and confirmed by modified the Curie–Weiss law. The combining relaxor and antiferroelectric properties with fine grain size by the incorporation of SBT enables an enhanced maximum polarization of a minimized P-E loop, leading to an improved BDS. As a result, a high recoverable energy density Wrec of 1.02 J/cm3 and a high energy efficiency η of 75.98% at 89 kV/cm were achieved for an optimum composition of 0.725 [0.94BNT-0.06BT]-0.275 SBT. These results demonstrate that BNT-based relaxor ferroelectric ceramics are good candidates for next-generation ceramic capacitors and offer a potential strategy for exploiting novel high-performance ceramic materials. Full article
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19 pages, 6897 KiB  
Article
On the Lanthanide Effect on Functional Properties of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 Ceramic
by Jacem Zidani, Ilham Hamdi Alaoui, Moneim Zannen, Eriks Birks, Zakaria Chchiyai, Mustapha Majdoub, Bouchaib Manoun, Mimoun El Marssi and Abdelilah Lahmar
Materials 2024, 17(8), 1783; https://doi.org/10.3390/ma17081783 - 12 Apr 2024
Cited by 6 | Viewed by 1780
Abstract
The beneficial effects of lanthanide incorporation into 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (BNT-BT) matrix on its functional properties were investigated. The conventional solid-state method was used for synthesizing samples. The structural refinement revealed that all samples crystallized in R3c rhombohedral [...] Read more.
The beneficial effects of lanthanide incorporation into 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (BNT-BT) matrix on its functional properties were investigated. The conventional solid-state method was used for synthesizing samples. The structural refinement revealed that all samples crystallized in R3c rhombohedral symmetry. Raman spectroscopy study was carried out using green laser excitation and revealed that no clear perceptible variation in frequency is observed. Dielectric measurements unveiled that the introduction of rare earth obstructed the depolarization temperature promoted in BNT-BT, the diffusive phase transition decreasing with increasing lanthanide size. Only dysprosium addition showed comparable diffusion constant and dielectric behavior as the unmodified composition. Further, the comparison of the obtained ferroelectric hysteresis and strain-electric field loops revealed that only Dy-phase exhibited interesting properties comparing parent composition. In addition, the incorporation of lanthanides Ln3+ into the BNT-BT matrix led to the development of luminescence characteristics in the visible and near infrared regions, depending on the excitation wavelengths. The simultaneous occurrence of photoluminescence and ferroelectric/piezoelectric properties opens up possibilities for BNT-BT-Ln to exhibit multifunctionality in a wide range of applications. Full article
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12 pages, 3555 KiB  
Article
High-Temperature Energy Storage Properties of Bi0.5Na0.5TiO3-0.06BaTiO3 Thin Films
by Ilham Hamdi Alaoui, Nathalie Lemée, Jamal Belhadi, Françoise Le Marrec, Anna Cantaluppi and Abdelilah Lahmar
Crystals 2023, 13(8), 1244; https://doi.org/10.3390/cryst13081244 - 12 Aug 2023
Cited by 4 | Viewed by 1637
Abstract
Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-BT) thin films were prepared via both chemical solution (CSD) and pulsed laser deposition (PLD). The structural, dielectric, and ferroelectric properties were investigated. High stability of the dielectric permittivity or TCC (∆ε/ε (150 °C) ≤ [...] Read more.
Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-BT) thin films were prepared via both chemical solution (CSD) and pulsed laser deposition (PLD). The structural, dielectric, and ferroelectric properties were investigated. High stability of the dielectric permittivity or TCC (∆ε/ε (150 °C) ≤ ±15%) over a wide temperature range from room temperature to 300 °C was obtained. Distinctly, the CSD film showed high TCC stability with variation of ±5% up to 250 °C. Furthermore, the CSD film showed an unsaturated ferroelectric hysteresis loop characteristic of the ergodic relaxor phase. However, the PLD one exhibited an almost saturated loop characteristic of the coexistence of both ergodic and non-ergodic states. The energy storage properties of the prepared films were determined using P–E loops obtained at different temperatures. The results show that these films exhibited a stable and improved energy storage density comparable to ceramic capacitors. Moreover, the CSD film exhibited more rigidity and better energy storage density, which exceeded 1.3 J/cm3 under a weak applied field of 317 kV/cm, as well as interesting efficiency in a large temperature range. The obtained results are very promising for energy storage capacitors operating at high temperatures. Full article
(This article belongs to the Special Issue Research Progress of Perovskite Ferroelectric Materials)
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11 pages, 4796 KiB  
Article
The Influence of BaTiO3 Content on the Energy Storage Properties of Bi0.5Na0.5TiO3-Bi(Mg2/3Nb1/3)O3 Lead-Free Ceramics
by Zhuo Li, Dandan Zhang, Chenbo Wang, Jiayong Zhang, Zixuan Wang, Zhuo Wang, Xin Yan, Tao Ai, Dawei Wang, Zhilun Lu and Yanhui Niu
Crystals 2023, 13(5), 733; https://doi.org/10.3390/cryst13050733 - 27 Apr 2023
Cited by 6 | Viewed by 2365
Abstract
Na0.5Bi0.5TiO3 (NBT)-based ceramics are promising lead-free candidates for energy-storage applications due to their outstanding dielectric and ferroelectric properties derived from large polarization. However, the high coercive field and large remnant polarization are unfavorable for practical applications, and thus [...] Read more.
Na0.5Bi0.5TiO3 (NBT)-based ceramics are promising lead-free candidates for energy-storage applications due to their outstanding dielectric and ferroelectric properties derived from large polarization. However, the high coercive field and large remnant polarization are unfavorable for practical applications, and thus NBT-based ceramics with relaxation behavior via doping/forming solid solutions with other elements/components have been widely studied. In this work, BaTiO3 (BT) was introduced to the 0.94Na0.5Bi0.5TiO3-0.06Bi(Mg2/3Nb1/3)O3 system by a conventional solid-state reaction to form a homogeneous solid solution of 0.94[(1−x)Na0.5Bi0.51TiO3-xBaTiO3]-0.06Bi(Mg2/3Nb1/3)O3 (BNT-100xBT-BMN). As the BT content increased, the proportion of the rhombohedral R3c phase increased while that of the tetragonal P4bm phase decreased, leading to the maximum Pmax (38.29 μC/cm2) and Eb (80 kV/cm) obtained in BNT-7BT-BMN (x = 0.07) composition. Specifically, the optimal energy storage properties of Wrec ~ 1.02 J/cm3 and η ~ 62.91% under 80 kV/cm were obtained in BNT-7BT-BMN ceramics, along with good temperature stability up to 200 °C, which are promising factors for future pulse power applications. Full article
(This article belongs to the Special Issue Advanced Dielectric Materials for Capacitor Application)
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13 pages, 2582 KiB  
Article
Fabrication of Lead-Free Bismuth Based Electroceramic Compositions for High-Energy Storage Density Applications in Electroceramic Capacitors
by Azam Khan, Taj Malook Khan, Jianbo Wu, Hazrat Bilal, Shahan Zeb Khan, Abdul Manan, Xiujian Wang and Noor Shad Gul
Catalysts 2023, 13(4), 779; https://doi.org/10.3390/catal13040779 - 21 Apr 2023
Cited by 3 | Viewed by 2520
Abstract
Lead-based electro-ceramic compositions are excellent energy storage materials used for high-energy storage density applications in dielectric ceramic capacitors. However, these materials have lead contents in their compositions, making them toxic, with a negative impact on human health and the environment. For this reason, [...] Read more.
Lead-based electro-ceramic compositions are excellent energy storage materials used for high-energy storage density applications in dielectric ceramic capacitors. However, these materials have lead contents in their compositions, making them toxic, with a negative impact on human health and the environment. For this reason, we synthesized a lead-free bismuth-based electro-ceramic perovskite, 0.80(0.92Bi1/5Na1/5TiO3-0.08BaTiO3)-0.20(Na0.73Bi0.09NbO3−xTa2O5), abbreviated (BNT-BT-NBN1−xTx), from mixed oxides with doping of tantalum (Ta) at different concentrations, using a conventional solid-state reaction method. The effects of Ta doping on the phase evolution, microstructure development, and energy storage applications were investigated. Detailed powder X-ray diffraction analysis revealed a pure perovskite phase with Ta doping at ≤0.05. Furthermore, it was observed that excessive addition of Ta has been resulted in secondary phase generation. Scanning electron microscopy validated the development of dense microstructures with a reduced grain size for the Ta concentration of ≤0.01. Electrochemical analysis revealed a maximum polarization (Pm) of ~22 µC/cm2 and a recoverable energy density of 1.57 J/cm3 with 80% efficiency for Ta doping at 0.05 with an applied field of 175 kV/cm. These results demonstrate the development of enhanced ferroelectric characteristics in an as-synthesized electro-ceramic perovskite for high-energy storage density applications in electro-ceramic capacitors. Full article
(This article belongs to the Special Issue Metal-Organic Frameworks in Electro and Photocatalysis)
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12 pages, 4355 KiB  
Article
Influence of the Addition of Rare Earth Elements on the Energy Storage and Optical Properties of Bi0.5Na0.5TiO3–0.06BaTiO3 Polycrystalline Thin Films
by Ilham Hamdi Alaoui, Mebarki Moussa, Nathalie Lemée, Françoise Le Marrec, Anna Cantaluppi, Delphine Favry and Abdelilah Lahmar
Materials 2023, 16(6), 2197; https://doi.org/10.3390/ma16062197 - 9 Mar 2023
Cited by 3 | Viewed by 2074
Abstract
Rare earth element-doped Bi0.5Na0.5TiO3–BaTiO3 (BNT–BT–RE) polycrystalline thin films were processed on a platinized substrate by chemical solution deposition. The microstructure, dielectric, and ferroelectric properties were investigated for all prepared films. It was found that the incorporation [...] Read more.
Rare earth element-doped Bi0.5Na0.5TiO3–BaTiO3 (BNT–BT–RE) polycrystalline thin films were processed on a platinized substrate by chemical solution deposition. The microstructure, dielectric, and ferroelectric properties were investigated for all prepared films. It was found that the incorporation of rare earth elements into the BNT–BT matrix increases both the dielectric constant and the breakdown strength while maintaining low dielectric losses, leading to an enhancement of the energy storage density to Wrec = 12 and 16 J/cm3 under an effective field of E = 2500 kV/cm, for Nd- and Dy-based films, respectively. The optical properties of films containing the lanthanide element were investigated and the obtained results bear interest for luminescence applications. The simultaneous appearance of ferroelectric and optical properties in the system under investigation is very promising for advanced optoelectronic devices. Full article
(This article belongs to the Special Issue Preparation and Properties of Novel Energy Storage Materials)
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11 pages, 4770 KiB  
Article
Fabrication and Characterization of Lead-Free BNT-6BT Ultrasonic Transducers Designed by an Intelligent Optimization Algorithm
by Junshan Zhang, Jianxin Zhao, Yi Quan, Jingrong He, Yi Li, Zhe Wang, Kun Zheng, Jian Zhuang, Zhishui Jiang, Li Wen and Wei Ren
Crystals 2022, 12(8), 1181; https://doi.org/10.3390/cryst12081181 - 22 Aug 2022
Cited by 2 | Viewed by 2751
Abstract
Lead-free piezoelectric material-based ultrasonic transducers have been researched for several years, but the inefficient properties and design difficulties have troubled lead-free ultrasonic transducers for a long time. To improve the performance and design efficiency of lead-free ultrasonic transducers, in this work, an equivalent [...] Read more.
Lead-free piezoelectric material-based ultrasonic transducers have been researched for several years, but the inefficient properties and design difficulties have troubled lead-free ultrasonic transducers for a long time. To improve the performance and design efficiency of lead-free ultrasonic transducers, in this work, an equivalent circuit model and intelligent optimization algorithm were combined for use in a transducer design. Firstly, 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3(BNT-6BT) lead-free piezoelectric ceramics were prepared and characterized. Then, BNT-6BT ceramics were used to fabricate the ultrasonic transducers. An equivalent circuit model-based software, PiezoCAD, and a genetic algorithm-based back-propagation neural network were used to optimize the design of the transducers. A 3.03 MHz center frequency and 60.3% −6 dB bandwidth of the optimized transducers were achieved, which were consistent with the neural networks optimization results. To verify the application potential of the lead-free transducers, tungsten rods phantom imaging and polystyrene spheres with 300 μm diameter manipulation were completed by the transducers, and the experiment results indicate that the BNT-6BT lead-free transducers have great potential in further biological and biomedical applications. Full article
(This article belongs to the Special Issue Lead-free Ferro-/Piezoelectric Ceramics and Thin Films)
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23 pages, 6993 KiB  
Article
Consistent Comparison of Remotely Sensed Sea Ice Concentration Products with ERA-Interim Reanalysis Data in Polar Regions
by Shuang Liang, Jiangyuan Zeng, Zhen Li, Dejing Qiao, Ping Zhang and Haiyun Bi
Remote Sens. 2020, 12(18), 2880; https://doi.org/10.3390/rs12182880 - 5 Sep 2020
Cited by 4 | Viewed by 3539
Abstract
Sea ice concentration (SIC) plays a significant role in climate change research and ship’s navigation in polar regions. Satellite-based SIC products have become increasingly abundant in recent years; however, the uncertainty of these products still exists and needs to be further investigated. To [...] Read more.
Sea ice concentration (SIC) plays a significant role in climate change research and ship’s navigation in polar regions. Satellite-based SIC products have become increasingly abundant in recent years; however, the uncertainty of these products still exists and needs to be further investigated. To comprehensively evaluate the consistency of the SIC derived from different SIC algorithms in long time series and the whole polar regions, we compared four passive microwave (PM) satellite SIC products with the ERA-Interim sea ice fraction dataset during the period of 2015–2018. The PM SIC products include the SSMIS/ASI, AMSR2/BT, the Chinese FY3B/NT2, and FY3C/NT2. The results show that the remotely sensed SIC products derived from different SIC algorithms are generally in good consistency. The spatial and temporal distribution of discrepancy among satellite SIC products for both Arctic and Antarctic regions are also observed. The most noticeable difference for all the four SIC products mostly occurs in summer and at the marginal ice zone, indicating that large uncertainties exist in satellite SIC products in such period and areas. The SSMIS/ASI and AMSR2/BT show relatively better consistency with ERA-Interim in the Arctic and Antarctic, respectively, but they exhibit opposite bias (dry/wet) relative to the ERA-Interim data. The sea ice extent (SIE) and sea ice area (SIA) derived from PM and ERA-Interim SIC were also compared. It is found that the difference of PM SIE and SIA varies seasonally, which is in line with that of PM SIC, and the discrepancy between PM and ERA-Interim data is larger in Arctic than in Antarctic. We also noticed that different algorithms have different performances in different regions and periods; therefore, the hybrid of multiple algorithms is a promising way to improve the accuracy of SIC retrievals. It is expected that our findings can contribute to improving the satellite SIC algorithms and thus promote the application of these useful products in global climate change studies. Full article
(This article belongs to the Special Issue Recent Advances in Cryospheric Sciences)
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19 pages, 5951 KiB  
Article
Lead-Free BNT–BT0.08/CoFe2O4 Core–Shell Nanostructures with Potential Multifunctional Applications
by Marin Cernea, Roxana Radu, Harvey Amorín, Simona Gabriela Greculeasa, Bogdan Stefan Vasile, Vasile Adrian Surdu, Paul Ganea, Roxana Trusca, Marwa Hattab and Carmen Galassi
Nanomaterials 2020, 10(4), 672; https://doi.org/10.3390/nano10040672 - 3 Apr 2020
Cited by 15 | Viewed by 4308
Abstract
Herein we report on novel multiferroic core–shell nanostructures of cobalt ferrite (CoFe2O4)–bismuth, sodium titanate doped with barium titanate (BNT–BT0.08), prepared by a two–step wet chemical procedure, using the sol–gel technique. The fraction of CoFe2O4 [...] Read more.
Herein we report on novel multiferroic core–shell nanostructures of cobalt ferrite (CoFe2O4)–bismuth, sodium titanate doped with barium titanate (BNT–BT0.08), prepared by a two–step wet chemical procedure, using the sol–gel technique. The fraction of CoFe2O4 was varied from 1:0.5 to 1:1.5 = BNT–BT0.08/CoFe2O4 (molar ratio). X–ray diffraction confirmed the presence of both the spinel CoFe2O4 and the perovskite Bi0.5Na0.5TiO3 phases. Scanning electron microscopy analysis indicated that the diameter of the core–shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two–phase composite nanostructures consisting of a BNT–BT0.08 core surrounded by a CoFe2O4 shell with an average thickness of 4–7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT–BT0.08/CoFe2O4 composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe2O4 semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mössbauer measurements have shown no change in the valence of the Fe3+, Co2+, Bi3+ and Ti4+ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT–BT0.08/CoFe2O4 core–shell composite potentially suitable for magnetoelectric applications. Full article
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14 pages, 3535 KiB  
Article
Electric-Field-Induced Phase Transformation and Frequency-Dependent Behavior of Bismuth Sodium Titanate–Barium Titanate
by Kai-Yang Lee, Xi Shi, Nitish Kumar, Mark Hoffman, Martin Etter, Stefano Checchia, Jens Winter, Lucas Lemos da Silva, Daniela Seifert and Manuel Hinterstein
Materials 2020, 13(5), 1054; https://doi.org/10.3390/ma13051054 - 27 Feb 2020
Cited by 15 | Viewed by 4215
Abstract
The electric field response of the lead-free solid solution (1−x)Bi0.53Na0.47TiO3xBaTiO3 (BNT–BT) in the higher BT composition range with x = 0.12 was investigated using in situ synchrotron X-ray powder diffraction. An introduced [...] Read more.
The electric field response of the lead-free solid solution (1−x)Bi0.53Na0.47TiO3xBaTiO3 (BNT–BT) in the higher BT composition range with x = 0.12 was investigated using in situ synchrotron X-ray powder diffraction. An introduced Bi-excess non-stoichiometry caused an extended morphotropic phase boundary, leading to an unexpected fully reversible relaxor to ferroelectric (R–FE) phase transformation behavior. By varying the field frequency in a broad range from 10−4 up to 102 Hz, BNT–12BT showed a frequency-dependent gradual suppression of the field induced ferroelectric phase transformation in favor of the relaxor state. A frequency triggered self-heating within the sample was found and the temperature increase exponentially correlated with the field frequency. The effects of a lowered phase transformation temperature TR–FE, caused by the non-stoichiometric composition, were observed in the experimental setup of the freestanding sample. This frequency-dependent investigation of an R–FE phase transformation is unlike previous macroscopic studies, in which heat dissipating metal contacts are used. Full article
(This article belongs to the Special Issue Functional Electroceramics)
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9 pages, 3355 KiB  
Article
Fabrication and Characterization of High-Frequency Ultrasound Transducers Based on Lead-Free BNT-BT Tape-Casting Thick Film
by Junshan Zhang, Wei Ren, Yantao Liu, Xiaoqing Wu, Chunlong Fei, Yi Quan and Qifa Zhou
Sensors 2018, 18(9), 3166; https://doi.org/10.3390/s18093166 - 19 Sep 2018
Cited by 9 | Viewed by 5535
Abstract
A lead-free 0.94(Na0.5Bi0.5) TiO3-0.06 BaTiO3 (BNT-BT) thick film, with a thickness of 60 μm, has been fabricated using a tape-casting method. The longitudinal piezoelectric constant, clamped dielectric permittivity constant, remnant polarization and coercive field of the [...] Read more.
A lead-free 0.94(Na0.5Bi0.5) TiO3-0.06 BaTiO3 (BNT-BT) thick film, with a thickness of 60 μm, has been fabricated using a tape-casting method. The longitudinal piezoelectric constant, clamped dielectric permittivity constant, remnant polarization and coercive field of the BNT-BT thick film were measured to be 150 pC/N, 1928, 13.6 μC/cm2, and 33.6 kV/cm, respectively. The electromechanical coupling coefficient kt was calculated to be 0.55 according to the measured electrical impedance spectrum. A high-frequency plane ultrasound transducer was successfully fabricated using a BNT-BT thick film. The performance of the transducer was characterized and evaluated by the pulse-echo testing and wire phantom imaging operations. The BNT-BT thick film transducer exhibits a center frequency of 34 MHz, a −6 dB bandwidth of 26%, an axial resolution of 77 μm and a lateral resolution of 484 μm. The results suggest that lead-free BNT-BT thick film fabricated by tape-casting method is a promising lead-free candidate for high-frequency ultrasonic transducer applications. Full article
(This article belongs to the Special Issue Ultrasound Transducers)
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