CaMg1−xLi2xSi2O6 microwave dielectric ceramics were prepared using talc as a low-cost Mg source in this work. The effects of Li+ substitution on phase composition, microstructure, densification, and dielectric properties were investigated. XRD results showed that all samples mainly formed a diopside-structured CaMgSi2O6 phase, with a small amount of the Ca2MgSi2O7 secondary phase. No Li-containing secondary phase was detected, indicating that Li+ entered the lattice when substituting for Mg2+. Rietveld refinement confirmed a gradual decrease in unit cell volume with increasing Li+ content. The talc-derived ceramics achieved high densification due to the highly reactive MgSiO3 and SiO2 generated during talc decomposition. Li+ substitution introduced cation vacancies, which promoted atomic diffusion and reduced the sintering temperature from 1300 to 1200 °C. At x = 0.04, the ceramics exhibited microwave dielectric properties: εr = 7.92, Q×f = 18,651 GHz, and τf = − 39.67 ppm/°C. The dielectric properties are governed not solely by intrinsic polarizability, but by its synergistic competition with extrinsic factors such as density, secondary phase, and microstructural uniformity. Overall, talc-based CaMg1−xLi2xSi2O6 ceramics provide a feasible low-cost route for high-frequency LTCC substrate applications.
The Cr3+/V3+ ions co-substituted Strontium–Barium (Sr0.5Ba0.5CrxVxFe12–2xO19 (x ≤ 0.10)) nanohexaferrites (NHFs) were produced by a one-pot sol–gel route. The structure, morphology, and electrical/dielectric properties were studied. X-ray powder diffraction (XRD) analysis confirmed the formation of hexagonal structured products without any impurity. The DXRD (crystallite size) of the products is between 32 and 46 nm. The dielectric and electrical properties of Sr0.5Ba0.5CrxVxFe12–2xO19 (x ≤ 0.10) NHFs were studied through dielectric constant, AC conductivity, and impedance analyses over a range of frequencies and temperatures. While AC conductivity exhibited a thermally activated hopping conduction, DC conductivity revealed bimode behavior with small polaron hopping occurring at high and low temperatures. Therefore, a semiconductor–metal-like transition was observed in the substituted NHFs. Thus, the dielectric constant and loss showed a strong frequency distribution, with substitution suppressing interfacial polarization at intermediate substitution levels, while re-emerging at higher concentrations. Electrical modulus analysis confirms non-Debye relaxation dynamics, and impedance spectroscopy shows that charge transport is thermally activated and dominated by resistive grain boundaries. A significant finding is that x systematically increases grain boundary resistivity, reducing overall conductivity while altering the relaxation behavior. Therefore, products offer insights for optimizing their performance in electronic and microwave device applications.
In this study, nanocrystalline FeS was prepared using a facile and easily scalable co-precipitation method and investigated for its performance as supercapacitor electrode. Phase pure hexagonal FeS was found by XRD analysis of synthesized FeS and the average crystallite size was calculated as 25.67 nm. Presence of characteristic Fe-S bonding was confirmed using FTIR spectrum and Fe/S states in FeS lattice was analyzed by XPS. Field-emission SEM analysis revealed that it possessed a porous, highly interconnected porous morphology comprising closely packed quasi-spherical nanoparticles and EDAX spectrum confirmed its composition and purity. In three-electrode configurations with 6 M KOH electrolyte, it displayed good battery-type faradaic activity with a high specific capacitance of 270 F g−1 at 4 A g−1. Charge storage mechanism was studied and from anodic and cathodic b values of 0.55 and 0.47, respectively, it was concluded that storage mechanism is diffusion controlled. EIS measurements showed that the electrodes have good charge transfer property and effective ion diffusion due to their highly porous structure. The FeS electrodes exhibited about 60
This study systematically investigates the influence of Eu/Bi partial substitution (0.00≤x≤0.10) on the microstructural, mechanical, electrical, and superconducting properties of Bi2.0-xEuxSr2.0Ca1.1Cu2.0Oy ceramics. Structural and functional characterization was performed by scanning electron microscopy, quantitative image analysis, bulk density, Vickers microhardness, temperature-dependent electrical resistivity, and critical-current–density measurements. Multi-criteria decision-making analysis was additionally employed to evaluate the general performance of the ceramic structures. Among the studied ceramic structures, Bi1.99Eu0.01Sr2.0Ca1.1Cu2.0Oy exhibits the most favorable combination of the investigated properties. Vickers microhardness analysis shows an indentation size effect, with the (x=0.01) composition exhibiting the highest hardness (0.53 GPa), elastic modulus (43.32 GPa), yield strength, and fracture toughness among the investigated samples. SEM and quantitative image analysis further reveal a comparatively dense and homogeneous microstructure for this composition, characterized by an average grain size of approximately 4.87 μm, porosity of approximately 1.43 T_c^onset and T_c^offset of approximately 84.30 and 83.36 K, respectively. The critical current density also reaches its maximum value of approximately 76 A/cm2 at this structure. Increasing the Eu/Bi substitution level beyond (x=0.01), however, is accompanied by progressive microstructural heterogeneity and deterioration of the mechanical and electrical characteristics. These experimental trends indicate that a limited level of Eu/Bi substitution can improve the structural integrity and functional performance of Bi-2212 ceramic structures, while excessive substitution leads to negative consequences. The multi-criteria decision-making analysis independently identifies the low substitution region, particularly (x=0.01), as the most favorable composition, providing quantitative support for the experimentally observed structure–property relationships. To sum up, all the results indicate that controlled Eu/Bi partial substitution serves as an effective compositional approach for simultaneously tailoring the microstructural, mechanical, densification, electrical, and superconducting characteristics of Bi-2212 ceramics.
Natural dye-sensitized solar cells face persistent challenges of narrow spectral response and limited photochemical stability that constrain practical deployment despite advantages in sustainability and cost. A recent demonstration of 6.82 _2 –SnO _2 core–shell photoelectrodes and platinum-coupled carbon counter electrodes. Chlorophyll extraction yielded solutions exhibiting Soret band absorption at 432 nm and Q-bands at 618 and 662 nm, complementing anthocyanin absorption at 532 nm. Sequential co-sensitization wherein photoelectrodes were immersed in chlorophyll solution for 12h followed by anthocyanin solution for 12h achieved optimal dye loading, delivering 8.47 ± 0.27 ^2 , open-circuit voltage of 0.62V, and fill factor of 0.73. The poly(ethylene oxide)–poly(vinylidene fluoride) gel electrolyte demonstrated ionic conductivity of 4.2 mS/cm at 25°C, sufficient for efficient charge transport while preventing electrolyte leakage and dye desorption. Incident photon-to-current efficiency measurements confirmed broadband photoresponse spanning 400–700 nm with dual maxima at 530 and 665 nm. Photoresponse remained above 40
Perovskite ceramic (Ba0.2Na0.2Bi0.2Sr0.2Ca0.2)(Mg0.08Ti0.92)O3 (BT-Mg) and (Ba0.2Na0.2Bi0.2Sr0.2Ca0.2)(Mn0.08Ti0.92)O3 (BT-Mn) were prepared via a citrate-combustion technology. High-entropy engineering was adopted to optimize domain structure and microstructure, thereby delaying saturation polarization and enhancing the electric breakdown field strength. Through two-step sintering, BT-Mg ceramic exhibits superior comprehensive energy storage performance (Wrec of 4.8 J/cm3 and η of 89.2
This study demonstrates a dual-band ambient radio-frequency (RF) energy-harvesting system based on a laser-induced graphene/Ag (LIG/Ag) conductive antenna integrated with a photocured ceramic-resin substrate. An LIG antenna pattern was directly formed on polyimide using a CO2 laser, followed by drop coating of a silver nitrate precursor and a second laser treatment to produce the LIG/Ag composite conductive structure. A previously reported CPW-fed antenna geometry was retuned for operation at 2.45 and 4.38 GHz. SEM observations revealed particles distributed over the porous LIG structure, while EDS analysis confirmed the presence and spatial distribution of Ag in the analyzed regions. Following the Ag-containing modification, the measured sheet resistance decreased from 20.4 to 13.1 Ω/sq, corresponding to a reduction of approximately 35.8
As global energy strategies shift toward renewable sources, there is an urgent requirement for innovative, low-toxicity energy storage materials showing promising electrochemical properties. This drives the development of advanced electrode materials rather than conventional electrodes in batteries such as lithium-ion and sodium-ion batteries. In this work, LaVO4–TiO2 (LV–TO) composite was synthesised via a simple solid-state route and evaluated as an anode material for lithium-ion batteries (LIBs). As far as we know, this is the first report on LaVO4–TiO2 composite for LIBs. The structural, morphological, and surface chemical properties were investigated using X-ray diffraction (XRD), Field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HRTEM) was used to understand its internal microstructure. To identify molecular vibrations, the nature of chemical bonds, and functional groups present in the sample, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) were carried out. The LV–TO exhibits an initial discharge capacity of 260 mAh/g, whereas the pristine shows only 193 mAh/g. LV–TO retains a discharge capacity around three times that of the pristine (149.6 vs. 53.5 mAh/g) after 65 cycles at 0.1 A/g. The improved performance results from effective contact at the LV–TO interface, which promotes charge transfer and enhances structural stability throughout cycling.
This report demonstrates the study of thermal, structural, vibrational, morphological, magnetic, and dielectric properties of sol–gel-synthesized Sr0.9Co0.1Fe11.9Nb0.1O19 annealed at 600 °C, 800 °C, 1000 °C, and 1200 °C for 4 h. The Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopy confirm the formation of metal–oxygen bonds corresponding to tetrahedral and octahedral sites, and the development of M-type hexagonal structure (space group P63/mmc), respectively. SEM images verified the annealing-induced grain growth and densification, resulting in the formation of well-defined hexagonal platelet-shaped and faceted grains characteristic of M-type strontium hexaferrite. Magnetic measurements showed improved ferromagnetic behavior with increasing annealing temperature, providing a maximum saturation magnetization (Ms) of 56.38 emu/g and remanent magnetization (Mr) of 26 emu/g at 1200 °C. Coercivity (Hc) peaked at 2211.58 Oe at 800 °C, with further increase in annealing temperature, Hc progressively decreased from 1664.39 to 797.99 Oe due to the transition from single-domain to multi-domain particles as evidenced from SEM images. Furthermore, the dielectric studies reveal high dielectric constant at low frequencies and low loss at high frequencies, while alternating current conductivity increases with increasing frequency due to electron hopping. Large Ms (56.38 emu/g) with low Hc (797.99 Oe) and low dielectric loss at high frequencies make Co–Nb co-doped strontium hexaferrite nanoparticles promising for high-frequency applications such as microwave absorbers, filters, and telecommunication devices.
Organic–inorganic metal halide perovskites (OIHPs) have emerged as promising photovoltaic materials for next-generation solar energy conversion due to their excellent optoelectronic properties and low-cost fabrication. However, the development of flexible perovskite solar cells (FPSCs) is limited by the poor thermal stability of polyethylene terephthalate (PET) substrates, which can deform or degrade during high-temperature processing. Conventional electron transport layers (ETLs), such as titanium dioxide (TiO2), require elevated annealing temperatures that are unsuitable for flexible devices. Therefore, this study investigated the optimisation of the annealing temperature of the SnO2 ETL for FPSCs fabricated on PET/ITO substrates with the architecture PET/ITO/SnO2/MAPbI3/P3HT/Cu. The SnO2 films were annealed at 110–160 ^∘C and characterised using ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Hall effect measurements. Photovoltaic (PV) performance was evaluated using current density–voltage (J–V) measurements. The results identified 150 ^∘C as the optimum annealing temperature, producing improved film uniformity, enhanced optical transmittance, reduced charge recombination, and lower electrical resistance without compromising the structural integrity of the PET substrate. The optimised device achieved a power conversion efficiency (PCE) of 5.29 ∼ 30 ^∘C ) without encapsulation. These findings demonstrate that optimised low-temperature SnO₂ processing is an effective strategy for enhancing the photovoltaic performance, mechanical flexibility, and long-term stability of FPSCs.
In this study, we have examined the role of hydrothermal (HD) and microwave (MW)-assisted synthesis method on neodymium cobaltite (NdCoO3) perovskite nanomaterials and their structural, morphological, and electrochemical properties changes for supercapacitor applications. X-ray diffraction (XRD) analysis confirms the successful formation of phase-pure orthorhombic NdCoO3 perovskites with enhanced crystallinity in hydrothermal-derived sample. Further, Raman and FTIR analyses validate the structural integrity and metal–oxygen bonding characteristics of the NdCoO3. FESEM and TEM analyses show a highly porous, interconnect network architecture of NdCoO3 and BET analysis demonstrates a significantly higher surface area and pore volume for the HD sample than MW sample which indicates superior mesoporosity. XPS elucidates phase-pure NdCoO3-HD with Nd3+ and Co3+ along with oxygen vacancies and surface defects that enhance electrochemical activity. Furthermore, electrochemical measurements conducted using a three-electrode system exhibited excellent pseudocapacitive behavior owing to reversible Co2+/Co3+ redox reactions. The NdCoO3-HD electrode shows a remarkable specific capacitance of 278 F/g at 1 A/g outperforming the MW sample at 202 F/g and also enhanced rate capability and lower internal resistance. HD sample shows an excellent cycling stability with 84.16
TiO2–MnO2 composite thick films were developed using the screen-printing technique with varying TiO2 contents (1–11 wt
The increase in stealth technology and advanced wireless communication systems has driven greater demand for lightweight, high-performance materials that support microwave-absorbing materials (MAMs). Despite their efficacy, several conventional absorbers continue to face drawbacks, including narrow absorption bandwidth, high density, and ineffective impedance matching. The purpose of the study was to investigate the impact of graphene oxide on the structural, magnetic, and electromagnetic properties of SrFe12O19/CNT hybrids, with emphasis on their performance as microwave absorbers in the 8–18 GHz frequency range. Advanced analytical techniques, including XRD, Raman spectroscopy, FESEM, VSM, and vector network analysis (VNA), were used to analyze phase formation, morphology, magnetic behavior, dielectric properties, and reflection loss (RL). The SrFe12O19/CNT/GO composite exhibited enhanced dielectric and magnetic relaxation behavior, with increased permittivity and conductivity, and synergistic magnetic–dielectric losses arising from interfacial polarization, dipolar relaxation, and ferromagnetic resonance. Cole–Cole analysis confirmed the presence of distributed relaxation processes arising from heterogeneous ferrite–CNT/GO interfaces, thereby enhancing microwave absorption performance in the X band region. The results for 20 wt
To address the inherent limitations of Li2Mg2.92Sn0.96O6 microwave dielectric ceramics, including high sintering temperature and poor temperature stability, while simplifying the traditional composite ceramics preparation process, a novel one-step in situ composite strategy was proposed in this study. BaCO3, V2O5, and low melting lithium fluoride (LiF) aid were simultaneously introduced to synthesize (1-x)Li2Mg2.92Sn0.96O6–xBa3(VO4)2–3 wt
Lead-free piezoelectric ceramics with the composition (0.996-x)K0.5Na0.5Nb0.96Sb0.04O3–0.004AlFeO3–xBi0.5K0.5HfO3 (abbreviated as KNNS-AF-xBKH, where x = 0.02, 0.025, 0.03, 0.035) were synthesized via a conventional solid-state reaction method. The effects of Bi0.5K0.5HfO₃ (BKH) doping concentration on the phase structure, Raman spectra, microstructure, and electrical properties were systematically investigated. Results indicate that the ceramic with x = 0.03, sintered at 1102 °C for 4 h, exhibits the optimal piezoelectric performance. X-ray diffraction (XRD) and Raman spectroscopy confirm that all samples crystallize in a perovskite structure at room temperature, with a coexistence of tetragonal and orthorhombic phases observed when x > 0.025. Scanning electron microscopy (SEM) analysis reveals a dense and uniform microstructure for the x = 0.03 composition. Through the synergistic doping of BKH and Sb5+-AlFeO₃, a near-room-temperature orthorhombic–tetragonal (O–T) polymorphic phase boundary (PPB) was constructed in KNN-based lead-free piezoelectric ceramics, accompanied by the induction of relaxor ferroelectric behavior, thereby achieving enhanced piezoelectric performance. Temperature-dependent dielectric measurements show that both the O–T phase-transition temperature and the Curie temperature shift toward lower temperatures with increasing BKH content. For x = 0.03, the dielectric loss tangent (tanδ) displays a non-monotonic temperature dependence, first increasing, then decreasing, before rising sharply at elevated temperatures. This composition also achieves a high remnant polarization (Pr = 40.5 μC/cm2), a notable piezoelectric coefficient (d33 = 232 pC/N), a low coercive field (Ec = 18.7 kV/cm), and a planar electromechanical coupling coefficient (kp) of 0.38.
This work introduces a humidity-sensitive and environmentally friendly flexible antenna that is based on a multilayer natural-fiber substrate and is used to monitor wounds. The antenna is in the 2.45 GHz ISM band and is stacked with a bamboo, banana, and pineapple-fiber mat dielectric constant of 3.92, 1.88 and 3.68 (respectively) and loss tangent of 0.01–0.02. In simulation, the proposed design is simulated to resonate at 2.466 GHz, and in experiment, at 2.52 GHz, with return losses of − 23.33 dB and − 39.03 dB, respectively. Characterization of material shows clearly functional benefits of each fiber layer, which is supported by reported moisture vapor transmission rates of 1780 g/m2/day (bamboo), 3033.70 g/m2/day (banana), and 15,440 g/m2/day (pineapple) to allow selectable diffusion of moisture throughout the substrate. An electromagnetic model that is sensitive to moisture has shown that as the moisture content is added (5–15
The growing demand for solar-blind deep-ultraviolet (DUV) photodetectors (PDs) is crucial for next-generation military, industrial, and civil optoelectronic applications. In this work, pristine monoclinic β-Ga2O3 nanowires were successfully synthesized on c-plane (0001) sapphire substrates via an Au/Pd-assisted vapor–liquid–solid (VLS) method using conventional chemical vapor deposition (CVD). The structural and compositional studies confirmed the growth of a pristine, stoichiometrically balanced monoclinic β-phase of Ga2O3. The morphological study revealed a highly uniform, nanowire morphology with an average diameter of 0.652 μm. To study the photodetection performance, 20 × 20 mm planar metal–semiconductor–metal (MSM) PDs were fabricated with Ag interdigitated electrodes over β-Ga2O3. The geometric configuration of the electrodes was systematically altered across three distinct designs to investigate the internal carrier transport and collection dynamics under a ±3 V bias. The optimized architecture, featuring a symmetric design with 1 mm electrode width and 1 mm interelectrode spacing, significantly outperformed alternative asymmetric or narrow-channeled devices. Under solar-blind DUV 254 nm illumination at 0.592 mW/cm2, this premier configuration achieved a maximum photocurrent of 0.89 A and the measured dark current of 0.15 A, yielding a peak spectral responsivity of 0.0527 A/W and a specific detectivity of 1.89 × 108 Jones. This superior performance is fundamentally attributed to an optimal local electric field distribution that minimizes carrier transit times and suppresses electron–hole recombination kinetics.
Zinc borosilicate glasses used in copper terminal electrode for multilayer ceramic capacitors (MLCCs) face the challenge of achieving low-temperature-sintering and strong interfacial bonding. Regulating the Mn valence state offers an effective strategy to meet this challenge. Here, a series of MnO2-doped ZnO–B2O3–SiO2–Al2O3–K2O glasses were designed by varying the K2O/Al2O3 molar ratio to modify the charge-compensation environment and Mn2+/Mn3+ distribution. As the K2O/Al2O3 molar ratio increased, the Mn valence distribution first shifted toward higher oxidation states and then partially shifted back toward lower oxidation states when the K2O/Al2O3molar ratio approached 1. This can be attributed to the highly polymerized network that suppressed the Jahn–Teller distortion of Mn3+. Among the investigated compositions, the sample with a K2O/Al2O3 molar ratio of 0.8 exhibited the most favorable characteristics, including a relatively depolymerized network, a lower glass transition temperature, minimal crystallization at 800 °C, and the favorable wettability. The corresponding copper paste achieved the lowest sheet resistance of 5.69 mΩ/□, the highest shear bond strength of 29.51 MPa, and excellent acid resistance. These results confirm that Mn valence engineering provides a novel strategy for optimizing low-temperature-sintering copper terminal electrodes for MLCC.
This study examines functionally graded ferrite–graphene–PVDF nanocomposites as a materials platform for broadband microwave absorption and electromagnetic interference shielding in 5G electronic systems. Nickel–zinc ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles and reduced graphene oxide nanosheets were incorporated into a PVDF matrix and arranged as a five-layer laminate with a controlled through-thickness composition gradient. The layered design was intended to combine magnetic loading, conductive filler connectivity, interfacial polarization, and local dielectric response while reducing the impedance-matching and filler agglomeration limitations commonly observed in homogeneous composites. Structural, morphological, and electromagnetic characterizations indicate that the graded laminate improves filler distribution, supports ferrite–graphene interfacial polarization, preserves interlayer integrity, and produces a gradual impedance transition. At an optimized thickness of 3.2 mm, the laminate achieved a minimum reflection loss of −62.4 dB at 18.3 GHz and an effective absorption bandwidth of 24.6 GHz. Its total EMI shielding effectiveness remains above 42 dB in the sub-6 GHz region and exceeds 54 dB across the measured X-, Ku-, K-, and Ka-band ranges, with absorption contributing more than 85
