Journal of Electroceramics最新文献

In this work, Density Functional Theory (DFT) has been employed to examine the structural, electronic, magnetic and optical characteristics of alkaline earth metals doped (Be, Mg and Ca) doped (Hf_1-xA_xO₂) alloys using the FP-LAPW (full-potential augmented plane wave plus local orbital) method and GGA and TB-mBJ exchange correlation methods. All studied compounds are structurally stable due to negative (formation energy) values. The computed results, including the band gap and lattice characteristics, correspond well with the existing experimental results. According to the band structure and density of states calculation, Hf_1-xA_xO₂ has wider band gaps for spin up configuration and reduced energy gaps of 4.71 3.41, 3.35 and 3.02 eV has been found for pure c-HfO₂, Hf_1-xMg_xO_2, Hf_1-xCa_xO₂ and Hf_1-xBe_xO₂ respectively. The PDOS results demonstrate that the formation of conduction and valance bands is due to Hf-6s orbitals and Mg/Ca/Be-s states. Additionally, we have investigated the optical characteristics that correspond to the real and imaginary portion of the dielectric function in the region of 0–12 eV, such as absorption coefficient, optical conductivity, refractive index, reflectivity and energy loss function. Moreover, Hf_1-xCa_xO₂ has a wide range of absorption in the UV-visible region, which indicates that this material is suitable for opto-electronic and solar cell applications. The refractive index suggests that Hf_1-xCa_xO₂ could be a potential candidate for applications to high-density optical data storage devices.

In this investigation, we report the synthesis of barium iron tantalate (BaFe_0.5Ta_0.5O₃; BFT) utilizing the molten salt method. The process yielded pure-phase perovskite powders at the relatively low calcination temperature of 700 °C. Subsequent fabrication of BFT ceramics from these calcined powders revealed notable properties. X-ray diffraction (XRD) analysis confirmed the cubic symmetry of the ceramics. All samples exhibited pronounced frequency-dependent dielectric behavior, with those sintered at 1,250 °C demonstrating particularly remarkable properties. Specifically, these ceramics achieved exceptionally high dielectric constants (ε_r ~ 5.30 × 10⁵ at 1 kHz and 230 °C). Impedance spectroscopic analysis revealed that the dielectric behavior of the ceramics can be attributed to the Maxwell–Wagner polarization mechanism, as the ceramics demonstrated heterogeneous conduction.

In the present era, the main aim of the researchers is to develop lead-free materials for ferroelectric material devices. Ceramics of perovskite compounds were successfully synthesized using a chemical decomposition method, with the composition (1-x) BiFeO₃-x(Bi K)TiMnO₃, where x was varied at 0.15 and 0.20. The average crystallite size for BKTM with 15% content and BKTM with 20% content was determined utilizing the Scherrer formula, resulting in 25.34 nm and 24.35 nm, respectively. The confirmation of compound creation was based on the analysis of Crystelloplotic XRD pattern data. The BKTM 15% exhibits an average grain size of 0.41 µm, while BKTM 20% shows 0.40 µm. Energy-dispersive X-ray analysis detected elements such as Bi, Fe, Na, K, Ti, and Mn. Modulus property exploration revealed non-Debye model relaxation behavior, which was observed particularly for sensor technology applications. To investigate the relaxation and conduction mechanisms in these samples were conducted at different temperatures and recurrence. Additionally, the scanning electron microscope (SEM) was employed to examine particle allocation and the location of grain boundaries. Impedance spectroscopic studies covered a wide temperature range (300 K-780 K) and a broad recurrence range (10³–10⁶ Hz). Complex plane and Impedance scale are semicircular arcs, which are related to the semiconducting character of the sample.

MgO ceramics with high density and superior properties were prepared from MgO powder using MgF₂ and Al₂O₃ as sintering aids via gelcasting and pressureless sintering. XRD, SEM and EDS were used to analyze the samples. The addition of MgF₂ and Al₂O₃ (with a ratio of Al₂O₃:MgF ₂ = 2–8:4) has been shown to enhance the densification and properties of MgO ceramics. This beneficial liquid phase may be attributed to the synergistic effects of liquid-phase sintering and spinelization reactions, which wet grain boundaries, promote particle rearrangement and mass transport, fill intergranular pores, and accelerate densification. At 1550 °C with an Al₂O₃:MgF ₂ ratio of 6:4, the MgO ceramics achieved optimal values for bulk density (3.331 g/cm³), thermal conductivity (39.2W/(m·K)), and flexural strength (63.15 MPa).

Silicon-graphite (Si/Gr) composite anode materials are essential for the advancement of high specific energy lithium-ion batteries (LIBs), yet their performances are often constrained by the interfacial interactions between Si and Gr. In this work, we used ball milling and plasma-assisted ball milling on Gr and nano-sized Si powders, followed by chitosan encapsulation and carbonization to synthesize SG@C and P-SG@C materials, respectively. Our findings indicated that plasma ball milling in an argon atmosphere promotes the exfoliation of Gr while facilitating the intercalation of Si particles within the Gr layers, thereby enhancing encapsulation by chitosan. Compared to SG@C, P-SG@C demonstrates superior initial specific capacity and Coulombic efficiency (CE), achieving a reversible specific capacity of 550.6 mAh/g with a capacity retention of 62.8% after 100 cycles at 0.5 A/g. Furthermore, we observed that the SG@C anodecharacterized by a random arrangement of Si and Gr resulting in degradation. In contrast, P-SG@C demonstrates a concurrent degradation pattern for both components. These observations underscore the advantages of plasma ball milling in optimizing the composite structure of Si and Gr, while highlighting how spatial distribution influences degradation mechanisms affecting anode performance.

This study explores the synthesis and characterization of lead-free (1-x)(Bi_0.5Na_0.5TiO₃) – x(KTa_0.55Nb_0.45O₃) (BNT-KTN55) ceramics for their potential for practical energy storage applications, at an electric field < 50 kV/cm. The research addresses the challenge of optimizing relaxor ferroelectric behavior to exhibit a thin P-E loop at this practically relevant electric field. In the study, X-ray diffraction (XRD) and Rietveld refinement confirmed a coexistence of rhombohedral (R3c) and tetragonal (P4bm) phases, with increasing tetragonal phase content as KTN55 doping increased. Scanning Electron Microscopy (SEM) revealed a significant reduction in grain size from 4.34 μm to 0.73 μm. Dielectric measurements showed typical relaxor ferroelectric behavior with frequency-dependent anomalies at T_s, T_m and a flat dielectric response in the range of 75° C to 310° C for higher doping levels. Ferroelectric measurements indicated a steady reduction in remnant polarization (P_r) and coercive field (E_c) with increasing KTN55 content. The composition with x = 0.06 demonstrated optimal performance, with a remnant polarization of 0.96 µC/cm², a maximum polarization of 14.42 µC/cm², and a discharge efficiency of 97.86% under a field of 43 kV/cm. The Recoverable energy density (W_rec) reached 0.295 J/cm³. All of the produced composite samples demonstrated stability without breakdown under the maximum applied electric field of 200 kV/cm, as limited by the instrument. Thus, their breakdown field exceeds this value, qualifying them as high breakdown field ceramics. These results suggest that BNT-KTN55 ceramics, particularly with x = 0.06, is a promising candidate for high-efficiency energy storage applications such as capacitors and pulse power devices.

In the last decades, BaMgF₄ based materials represent key systems for several optical applications. The present study explores the optimization of sol-gel conditions for producing pure BaMgF₄ thin films on Si (100) substrates by varying precursor ratios and annealing temperatures. Three approaches were examined using different molar ratios of [Ba(hfa)₂•tetraglyme] to [Mg(hfa)₂•2H₂O]•2diglyme. The synthetic method combines sol-gel and spin-coating techniques, utilizing the fluorinated β-diketonate [Ba(hfa)₂•tetraglyme] and [Mg(hfa)₂•2H₂O]•2diglyme as single-source precursors. X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and scanning electron microscopy (SEM) analysis were employed to characterize film composition, crystalline phases, and morphology. The study underscores the critical role of precursor hydrolysis efficiency, with the [Ba(hfa)₂•tetraglyme] precursor demonstrating superior performance in producing good-quality BaMgF₄ films. These findings provide insights into precise control over precursor chemistry and processing conditions, essential for optimizing film quality and advancing potential applications in optoelectronic devices.

Present work focussed on the preparation and characterization of ferroelectric ceramic-polymer composites, specifically using Poly Vinylidene Fluoride (PVDF) as the polymer host and PbZr_0.48Ti_0.52O₃(PZT), Bi_0.5Na_0.5TiO₃ (BNT) ceramics as the filler. The composites were prepared using the solution casting technique, and various properties were examined under different experimental conditions. The composites were characterized for various properties, including structural, microstructural, vibrational (FTIR-Fourier Transform Infrared), dielectric, and ferroelectric properties. XRD (X-ray Diffraction) analysis was used to observe the electroactive β-phase fraction in the composites. The microstructure of the composites was examined to understand the arrangement of the components. FTIR analysis provided insights into the mechanism of enhancing the β-phase and the interaction between negatively surface-charged ions of the PZT/BNT (BP) filler and the CH₂ dipole of the PVDF polymer matrix. Dielectric constant variation with PZT/BNT (BP) filler concentrations was studied. The interplay between functional properties and the β-phase, likely related to ferroelectric behaviour, was discussed in detail. The electroactive β-phase fraction was observed to increase in the ternary composite PVDF/PZT/BNT (BPP). For PVDF/PZT (PP) composite concentration, β-phase fraction decreased because of percolation effect. The study explores the comprehensive characterization of ferroelectric ceramic-polymer composites, focusing on the interaction between the polymer matrix and piezoceramic (PZT/BNT) (BP) filler. The observed changes in properties, especially the electroactive β-phase fraction, provide valuable insights into the composition-structure-property relationships in these composites. The work sheds light on the potential applications and optimization of these composites for capacitive applications.

The natural abundance and potential cost benefits of sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) make them increasingly appealing as viable substitutes to lithium-ion batteries (LIBs). Nonetheless, the progress of PIBs and SIBs is significantly hindered by the limited poor rate capability and mediocre cycling durability attributed to the huger ionic radius of K⁺ and Na⁺ in comparison to Li⁺. Herein, MoO₂/N-doped carbon nanoribbons with rich oxygen vacancies (OVs) have been prepared via hydrothermal method followed by thermal annealing in Ar atmosphere. The composite nanoribbons, as novel anode materials, demonstrate excellent electrochemical performance with a specific capacity of 132.6 mAh g^− 1 at 5 A g^− 1 for SIBs and 130.2 mAh g^− 1 at 1 A g^− 1 for PIBs, along with a high Coulombic efficiency of approximately 100% over 2000 cycles for SIBs and 10,000 cycles for PIBs. The highly conductive N-doped carbon significantly facilitates electron transfer, effectively suppress volume expansion, and increase additional sodium and potassium storage sites. A built-in electric field at heterojunction interface is beneficial for Na/K ions diffusion across the interface. Novelty, the rich OVs in MoO₂ lattices could induce built-in electric field around localized oxygen-vacancies, accelerating the migration of Na/K ions based on built-in electric field (BIEF) and percolation-channel model.

The development of high-performance silicon/silicon oxide (Si/SiO_x) anodes has attracted great attention in the field of next-generation high-energy lithium-ion batteries (LIBs). However, preparing effective Si/SiO_x composite materials to address issues such as poor cycling stability, subpar initial coulombic efficiency (ICE), and subpar interface compatibility remains a challenge. This work proposes a simple strategy for preparing Fe/Fe₃C particle modified thin-layer carbon-coated Si/SiO_x composite materials using a mixture of resorcinol formaldehyde (RF) precursor pyrolysis and ultrasonic treatment (referred to as C@Si/SiO_x-Fe/Fe₃C, abbreviated as CSSO-Fe/Fe₃C). These composite materials are used as anodes for LIBs. Exploiting the benefits of its structure and composition, the CSSO-Fe/Fe₃C anode offers a high ICE value of 68.7% and maintains a capacity of 563.2 mAh g⁻¹ even after 1200 cycles at a current density of 2.5 A g⁻¹. Comprehensive characterization and electrochemical studies have elucidated the interface compatibility and structural stability mechanisms induced by the small amount of Fe/Fe₃C doping and carbon coating, which explain the high capacity and stable cycling performance. Furthermore, when paired with LiCoO₂ cathode, the assembled LiCoO₂||CSSO-Fe/Fe₃C coin-type full battery has a capacity of 80.7 mAh g⁻¹ and a capacity retention rate of 76.6% after 200 cycles at 1.0 C. This synthesis approach offers valuable insights for designing high-performance Si/SiO_x electrode materials.