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Influence of Gd Substitution on the Crystal and Defect Structure of BaTi₀.₉₆₅Sn₀.₀₃₅O₃ Ceramics

2026-07-01T00:00:00Z

Title: Influence of Gd Substitution on the Crystal and Defect Structure of BaTi₀.₉₆₅Sn₀.₀₃₅O₃ Ceramics Authors: Poonia, Kanika; S Kundu, R; Ahlawat, Neetu; Singh Lather, Aryan; Singroha, Rinku; Parmar, Rajesh; Kumar, Vinay Abstract: Polycrystalline Ba1-xGdₓTi0.965Sn0.035O3 (x = 0.00, 0.025, 0.05, 0.075) ceramics were synthesised via a solid-state route to investigate the effect of Gd³⁺ on the structural and microstructural properties of barium tin titanate (BTS). X-ray diffraction (XRD), supported by Rietveld refinement, confirmed a well-crystallised orthorhombic phase (Amm2) with systematic peak shifts indicating successful Gd incorporation. In contrast, a pyrochlore-type Gd₂Ti₂O₇ secondary phase appeared at higher Gd contents (0.025 > x ≥ 0.05), marking the solubility limit. Williamson– Hall Plots showed that Gd doping reduces lattice strain while preserving long-range crystallinity. Electron-density contour and 3D Fourier maps revealed a periodically ordered lattice with subtle local rearrangements induced by Gd³⁺. FTIR spectra evidenced Ti–O vibrational modes alongside the disappearance of carbonate-related bands. The grain size, as calculated from FESEM micrographs, decreases from 0.721 µm to 0.289 µm due to the solute drag mechanism and the emergence of a secondary phase. Energy-dispersive spectroscopy confirms the elemental makeup of the synthesized samples. Raman spectroscopic analysis agrees well with the XRD studies. These structural and microstructural modifications establish a strong foundation for subsequent investigations into the enhanced dielectric and ferroelectric properties of Gd-modified BTS, highlighting its potential as a lead-free material for advanced capacitors, actuators, sensors, and energy-storage devices. Page(s): 707-720

Quantitative analysis of CME-Flare Coupling and their influence on Solar Energetic Particle Events (1997-2024)

2026-07-01T00:00:00Z

Title: Quantitative analysis of CME-Flare Coupling and their influence on Solar Energetic Particle Events (1997-2024) Authors: Bhoj, Chandrasekhar; P Verma, L Abstract: Solar energetic particles (SEPs) are major contributors to space weather conditions, especially protons with energies greater than 10 MeV, because they provide a critical scientific insight about the solar interplanetary processes. the relation between SEP flux and solar drivers (i.e., coronal mass ejections (CMEs) and solar flares) is discussed. For this, data collected between 1997-2024 were used; a total of 140 events were identified during this period, out of which around 75 % SEP events are linked with Halo CMEs. SC 23 has the most SEP events (87), followed by SC 24 (40) and SC 25 (13). Also, the study of the occurrence of SEP events with CME speed reveals that approximately 52 % SEP events were associated with fast CMEs (Speed>1400 km/s), 28 % with moderate CMEs (1000–1400 km/s), and approximately 20 % with slow speed CMEs (Speed<1000 km/s). When the relationship between SEP events and CME-associated solar flares was investigated, it was found that more than 70 % of SEP-flare-related events originated from the western solar hemisphere, 30 % originated from the eastern hemisphere, and almost equal numbers of the SEP events are associated with northern and southern hemisphere-oriented solar flares. It was also found that approximately 50 % of SEP events are associated with M class solar flares, 29 % with X-class solar flares and only 21% with C-class solar flares. Finally, Regression and correlation analyses were conducted between the CME speeds and SEP Flux intensities, and separate fitted regression lines for each cycle indicate that they are in favour of the evident trend of a larger SEP flux with a faster CME speed and reflect a progressively stronger correlation. These findings illustrate that the CME dynamics and flare properties play a strong role in SEP production and propagation. For efficient space weather forecasting and satellite protection, it is important to monitor the real-time solar flare locations and CME parameters. Page(s): 721-729

Bias-Field-Dependent Impedance and Phase Characterization of a Ferroelectric Liquid Crystals Relevant to Display Applications

2026-07-01T00:00:00Z

Title: Bias-Field-Dependent Impedance and Phase Characterization of a Ferroelectric Liquid Crystals Relevant to Display Applications Authors: Sarathi Bhattacharyya, Surjya; Mukherjee, Amrita Abstract: Phase transition and dielectric relaxation dynamics of a ferroelectric liquid crystal (FLC) material were investigated across the SmC*–N* phase transition using differential scanning calorimetry (DSC) and impedance spectroscopy under applied DC bias fields. Dielectric spectra recorded under DC bias exhibit anomalous low-frequency behavior in the vicinity of the SmC*–N* transition. A pronounced enhancement of low-frequency dielectric absorption is observed at low DC bias fields, followed by suppression at higher bias fields near ~72 °C, accompanied by the presence of the conventional Goldstone mode at slightly higher frequencies. The dielectric response over a wide temperature range, analyzed using a Cole–Cole–modified Debye model in both biased and unbiased conditions, reveals significant variations in the relaxation parameters. The low-frequency relaxation process close to the SmC*–N* transition is attributed to the combined contributions of the Goldstone mode and domain-related dynamics, as evidenced by the anomalous DC bias dependence of the dielectric parameters. The temperature dependance of relaxation parameters under DC bias exhibits conventional Goldstone-mode-like behavior due to suppressed domains and field-induced alignment of the spontaneous polarization.Phase transition and dielectric relaxation dynamics of a ferroelectric liquid crystal (FLC) material were investigated across the SmC*–N* phase transition using differential scanning calorimetry (DSC) and impedance spectroscopy under applied DC bias fields. Dielectric spectra recorded under DC bias exhibit anomalous low-frequency behavior in the vicinity of the SmC*–N* transition. A pronounced enhancement of low-frequency dielectric absorption is observed at low DC bias fields, followed by suppression at higher bias fields near ~72 °C, accompanied by the presence of the conventional Goldstone mode at slightly higher frequencies. The dielectric response over a wide temperature range, analyzed using a Cole–Cole–modified Debye model in both biased and unbiased conditions, reveals significant variations in the relaxation parameters. The low-frequency relaxation process close to the SmC*–N* transition is attributed to the combined contributions of the Goldstone mode and domain-related dynamics, as evidenced by the anomalous DC bias dependence of the dielectric parameters. The temperature dependance of relaxation parameters under DC bias exhibits conventional Goldstone-mode-like behavior due to suppressed domains and field-induced alignment of the spontaneous polarization. Page(s): 730-736

Frequency Stabilization of Renewable Energy Sources and Redox Flow Battery Integrated Three Area Power System Using Cascade Controller

2026-07-01T00:00:00Z

Title: Frequency Stabilization of Renewable Energy Sources and Redox Flow Battery Integrated Three Area Power System Using Cascade Controller Authors: Ishwar Vais, Ram; Pal Singh, Vijay; Singh, Mratyunjay; Tripathi, Ashish; Kumar, Sarvesh; Chiranjeevi, Tirumalasetty Abstract: This paper proposes a novel cascaded PID–TID (proportional–integral–derivative and tilt–integral–derivative) control strategy for a three-area interconnected power system integrating a thermal system (TS), wind turbine system (WTS), electric vehicles (EVs), and a redox flow battery (RFB) as an energy storage device (ESD). A comprehensive MATLAB/Simulink model of the system is developed to evaluate dynamic performance under varying operating conditions. The controller parameters are optimally tuned using the Mayfly Optimization Algorithm (MOA) to ensure superior control action. The effectiveness of the proposed cascaded PID–TID controller is validated through comparative analysis with conventional standalone PID and TID controllers. Simulation results demonstrate that the proposed approach significantly enhances oscillation damping, reduces settling time, and minimizes peak overshoot and undershoot. In addition, the impacts of WTS, EVs, and ESD integration on system dynamics are systematically investigated, showing notable improvements in frequency regulation and transient stability. Sensitivity analysis further confirms the robustness and reliability of the proposed control scheme, indicating its suitability for modern multi-area power systems with high penetration of renewable energy sources. Page(s): 737-745