Browsing by Author "Emmanuel, Marwa"

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    0.98[(Na(1–x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 Lead-free Ceramic System Design; An antiferroelectrics with Improved Relaxation Behavior
    (Elsevier BV, 2023) Emmanuel, Marwa
    The sodium niobate-based ceramics 0.98[(Na(1−x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 acronymed NSmNT of different compositions (x = 0.05, 0.1, 0.11, 0.12, and 0.13) were prepared via solid-state reaction method. The prepared samples were characterized by XRD to study the phase structure of the designed systems, SEM to study the microstructure properties of the NSmNT ceramics. In addition to that LCR meter was used to measure the sample temperature-dependent dielectric permittivity, dielectric loss, and systems impedance. The results showed an increment in the dielectric breakdown strength (DBS) with increasing x content from 100 kVcm–1 to 450 kVcm–1. Similarly, the high recoverable energy density (Wrec) of 5.61 J cm–3 was obtained for x = 0.11 symbolized (NSmNT2) with an exquisite efficiency of 88%. The study also analyzed the complex impedance of the NSmNT2 ceramics system to clearly understand the dielectric behavior of the system in question. A general view of things considers the NSmNT2 ceramic system to be a reliable system for pulsed power applications.
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    0.98[(Na(1–x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 Lead-free ceramic system sesign; an antiferroelectrics with improved relaxation behavior
    (Elsevier BV, 2023) Emmanuel, Marwa
    The sodium niobate-based ceramics 0.98[(Na(1−x)/2Smx/2Nb0.3TiO3)] + 0.02MnO2 acronymed NSmNT of different compositions (x = 0.05, 0.1, 0.11, 0.12, and 0.13) were prepared via solid-state reaction method. The prepared samples were characterized by XRD to study the phase structure of the designed systems, SEM to study the microstructure properties of the NSmNT ceramics. In addition to that LCR meter was used to measure the sample temperature-dependent dielectric permittivity, dielectric loss, and systems impedance. The results showed an increment in the dielectric breakdown strength (DBS) with increasing x content from 100 kVcm–1 to 450 kVcm–1. Similarly, the high recoverable energy density (Wrec) of 5.61 J cm–3 was obtained for x = 0.11 symbolized (NSmNT2) with an exquisite efficiency of 88%. The study also analyzed the complex impedance of the NSmNT2 ceramics system to clearly understand the dielectric behavior of the system in question. A general view of things considers the NSmNT2 ceramic system to be a reliable system for pulsed power applications.
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    Enthralling storage properties of (1–x)La0.03Na0.91NbO3–xBi(Li0.5Nb0.5)O3 lead-free ceramics: high energy storage applications
    (American Chemical Society, 2020) Emmanuel, Marwa; Hao, Hua; Liu, Hanxing; Appiah, Millicent; Jan, Abdullah; Ullah, Atta; Ullah, Amjad
    The current work presents the designed series of compositions within pseudocubic regions based on (1–x)La0.03Na0.91NbO3–xBi(Li0.5Nb0.5)O3 ceramics abridged as (1–x)LNN–xBLN meant for energy storage applications. The addition of Bi(Li0.5Nb0.5)O3 (BLN) considerably disrupted the ferroelectric order of the La0.03Na0.91NbO3 (LNN) ceramics and favored the perfection of the energy storage density properties. Material properties like breakdown strength (BDS), charge–discharge efficiency (η), and dielectric loss of the system were enhanced via the incorporation of BLN into LNN. The external electric field supply into the system drastically enlarged the energy storage density, where the maximum recoverable energy density value of 2.02 J cm–3 at 300 kV cm–1 was achieved in 0.88LNN–0.12BLN ceramics. Besides this, the new system also demonstrates a strong ability to withstand stress (fatigue-free character) and sound temperature stability characteristics. The impressive storage density, temperature stability, cycle stability, and frequency stability credited to a steady relaxor pseudocubic phase covering a broad temperature range describes the newly designed system. The results demonstrate the potential for the (1–x)LNN–xBLN ceramics as the promising lead-free energy storage materials.
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    Modified Sodium niobate-based 0.76(NaNbO3)-0.24(Sr0.55La0.3TiO3) ceramics for energy storage
    (Elsevier BV, 2023) Emmanuel, Marwa
    Because of their fast discharge speed and excellent fatigue resistance, dielectric ceramics are highly sought after for electronic systems. However, the low energy density caused by the low breakdown electric field leads to poor volumetric efficiency, which is the main challenge for dielectric ceramics in practical applications. Through a ramp-soak-spike (RSS) strategy, we propose a system based on lead-free materials (Sodium niobate precursors) with an enhanced breakdown electric field, resulting in an exquisite energy storage density within perovskite NaNbO3-based ceramics. The current study developed a superior 0.76(NaNbO3)-0.24(Sr0.55La0.3TiO3) ceramics system, abbreviated ME-RSS, for ramp-soak-spike sintering with a high recoverable energy density (Wrec) of 5.8 J cm−3, an efficiency (η) of 85% and high breakdown strength of approximately 440 kVcm−1. Despite these remarkable properties, the system can withstand a high number of cycles as well as a high charge-discharge speed. The current study proposes NaNbO3-based ceramics designed via a RSS sintering route through doping to improve dielectric ceramic breakdown strength, which is expected to benefit a wide range of dielectric ceramic applications requiring high breakdown strength, such as high-voltage capacitors and electrocaloric solid-state cooling devices.
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    Modified Sodium niobate-based 0.76(NaNbO3)-0.24(Sr0.55La0.3TiO3) ceramics for energy storage
    (Elsevier BV, 2023-09) Emmanuel, Marwa
    Because of their fast discharge speed and excellent fatigue resistance, dielectric ceramics are highly sought after for electronic systems. However, the low energy density caused by the low breakdown electric field leads to poor volumetric efficiency, which is the main challenge for dielectric ceramics in practical applications. Through a ramp-soak-spike (RSS) strategy, we propose a system based on lead-free materials (Sodium niobate precursors) with an enhanced breakdown electric field, resulting in an exquisite energy storage density within perovskite NaNbO3-based ceramics. The current study developed a superior 0.76(NaNbO3)-0.24(Sr0.55La0.3TiO3) ceramics system, abbreviated ME-RSS, for ramp-soak-spike sintering with a high recoverable energy density (Wrec) of 5.8 J cm−3, an efficiency (η) of 85% and high breakdown strength of approximately 440 kVcm−1. Despite these remarkable properties, the system can withstand a high number of cycles as well as a high charge-discharge speed. The current study proposes NaNbO3-based ceramics designed via a RSS sintering route through doping to improve dielectric ceramic breakdown strength, which is expected to benefit a wide range of dielectric ceramic applications requiring high breakdown strength, such as high-voltage capacitors and electrocaloric solid-state cooling devices.
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    Significantly enhanced energy storage density of NNT ceramics using aliovalent Dy3+ Dopant
    (American Chemical Society, 2021) Emmanuel, Marwa; Hao, Hua; Liu, Hanxing; Jan, Abdullah; Alresheedi, Faisal
    Sodium niobate (NN)-based lead-free ceramic DyxNa1–x(Nb0.9Ta0.1)O3 denoted as (DNNT) x = 0, 0.05, 0.1, 0.2, and 0.3 was synthesized via a conventional solid-state method to achieve bulk lead-free dielectric ceramics having an improved energy storage capability that can conceivably be used in pulsed power technology. The addition of Dy3+ broadened the phase transition peak, thereby strengthening the relaxor properties of the DNNT ceramic materials. The sample’s microstructure was explored using a scanning electron microscope, and its corresponding phase structure via X-ray diffraction (XRD). A systematic study was carried out for energy storage properties of 0.2 mol of Dy3+ (DNNT20) where a recoverable energy storage density (Wrec) of 4.61 J cm–3 with a breakdown strength (BDS) of 478 kV cm–1 and an energy storage efficiency (η) of ≈84% were achieved. Additionally, the DNNT20 ceramics displayed comparatively reasonable temperature stability (20–140 °C), excellent frequency stability (0.1–100 Hz), and also fast charge–discharge speed (≤0.5 μs). Thus, the DNNT20 ceramic materials can be of probable use for future energy storage applications.