arXiv subjects

Somaditya Sen

Publications and source records attributed to Somaditya Sen.

At least 19 recordsLinked to original sources

arXiv2026

Distribution of Relaxation Times analysis of evolution of Oxygen Reduction Pathways for ionic conductor infiltration on MIEC cathode

Solid oxide fuel cells (SOFCs) are promising electrochemical energy conversion devices; however, the sluggish cathodic oxygen reduction reaction (ORR) remains a major limitation for intermediate-temperature operation. ORR subprocesses can be modified by infiltrating ionic Sm0.2Ce0.8O2-delta (SDC) on mixed ionic electronic SrFe0.9Ti0.1O3-delta (STF). However, the processes are indistinguishable in most cases and poorly understood using conventional equivalent circuits. Distribution of Relaxation Times (DRT) analysis distinguishes these processes to identify the dynamics with temperature and surface reconstruction. Such analysis is being reported, revealing the connection between increase of active sites, temperature, and polarization resistance (RP). SDC infiltration preferentially accelerates oxygen surface exchange and activation processes over the relatively high frequency charge transfer process related to cathode surface at elevated temperatures for the infiltrated cells. RP was reduced substantially with the systematic redistribution of each process to as low as 0.04 ohm.cm2 at 800 degC. This work underlines the deconvolution of the processes using DRT as a tool, and SDC infiltrated STF as a model cathode system to provide a mechanistic insight of understanding ORR kinetics and design a rationale for developing high-performance SOFC air electrodes

cond-mat.mtrl-sci↗

arXiv2025

Increased Covalence and V-center mediated Dark Fenton-Like Reactions in V-doped TiO2: Mechanisms of Enhanced Charge-Transfer

Tuning the valence state and electronic structure of catalytically active sites is crucial for improving Fenton and Fenton-like reactions, which rely on the efficient activation of the H2O2 molecule. Pure TiO2, however, has inadequate activity towards the H2O2 activation and is often constrained by the intrinsic electronic limitations of pristine TiO2. Herein, a rational approach has been demonstrated to improve the Fenton-like catalytic performance of TiO2 through multivalent vanadium (V) doping. A comprehensive characterization using X-Ray Diffraction (XRD), Raman spectroscopy, UV-Vis spectroscopy, X-Ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), and Density functional theory (DFT) reveals that V incorporation substantially alters the electronic structure of TiO2. The DFT results, supported by experimental data, indicate that V doping enhances Ti-O covalence and introduces mid-gap states, resulting in a reduced band gap and improved charge transfer. XPS confirms the coexistence of multiple oxidation states of V, which serve as active centres for activating H2O2 and generating OH radicals. As a result, V-doped TiO2 exhibits significantly enhanced dark-catalytic activity in degrading the organic dye Rhodamine B (RhB). Overall, this study provides fundamental insights into multivalent-cation-induced valence state and electronic structure modulation in TiO2, offering a promising strategy for designing high-performance catalysts via defect engineering for sustainable environmental remediation.

cond-mat.mtrl-sci↗

arXiv2025

Interfacial Synergy in Ag-Doped CuO-AgCl-g-C3N4 Composites for Efficient Charge Separation and Low-power Methylene Blue Degradation

An Ag-doped CuO-AgCl-g-C3N4 heterostructure has been designed to achieve rapid Methylene Blue (MB) degradation through a synergistic photo-Fenton mechanism driven by low-power UV illumination. The composite integrates narrow-bandgap CuO, plasmonic Ag/AgCl, and visible-responsive g-C3N4 into a dual Z-scheme configuration that promotes efficient interfacial charge transfer while preserving strong redox potentials. Diffuse reflectance UV-Vis spectra ascertained the bandgap positions of the composite corresponding to those of its constituents: 2.9 eV (g-C3N4) and 1.42 eV (Ag-doped CuO-AgCl), indicating enhanced absorption and efficient charge carrier generation. BET analysis confirmed the presence of mesoporosity and revealed an effective surface area, ensuring the availability of abundant adsorption and reaction sites. A commercial 11 W UV irradiation was used for the photocatalytic test. Almost complete degradation of MB occurred within 10 min, following pseudo-first-order kinetics with a high apparent rate constant of 0.45/min. The remarkable activity arises from the synergistic interplay of Fenton-like redox cycling and efficient photoinduced charge carrier generation and separation. In addition, it has been demonstrated that intentionally incorporated AgCl plays an active role as a plasmonic-semiconducting interface, strengthening charge separation and catalyst stability under neutral conditions, rather than acting as a passive chloride byproduct. Overall, by linking defect engineering, heterojunction design, and photo-Fenton synergy, this study establishes a low-power, catalytic platform offering a viable pathway towards sustainable dye wastewater remediation.

cond-mat.mtrl-sci↗

arXiv2025

Hexagonal polymorphism induced structural disorder and dielectric anomalies of Ca/Mn modified BaTiO3

This work involves the local structural investigation of the samples using Extended X-ray Absorption Spectra (EXAFS) analysis to investigate structural changes due to the Ca and Mn-modified BaTiO3. TEM investigation of the crystal structure reveals the coexistence of the tetragonal and hexagonal phases of BaTiO3. Band gap modification and Urbach tail variation in UV-DRS measurements reveal a reduction of band gap from UV to Visible range (3.2 eV to 2 eV). This band gap change is correlated with the valence band modification observed in PES measurements due to localised defects in the material, and supported by theoretical Density of States calculations. The electron localisation function calculation is used to analyse the changes in the localised electron density near the dopant atoms. It reveals the local expansion and contraction of the lattice surrounding the dopant atom. All these structural modifications lead to variations in the dielectric properties and diffusive nature of the phase transition. The defect-induced structural modifications, multiple phase coexistence, band gap variations and dielectric properties are explored and correlated.

cond-mat.mtrl-sci↗

arXiv2025

An indirect correlation of dielectric properties using optical trapping and dielectric resonance in two different frequency regimes

Dielectric permittivity, $\varepsilon_r$, of materials are often limited to a sub-GHz range using normal LCR meters. In the GHz range the $\varepsilon_r$ can be measured using Vector Network Analyzers and measurement jigs (waveguides) which are specific for different frequency regimes. Hence, to measure er for the entire frequency range one needs several components and is an extremely costly experiment. However, for applications such as Dielectric Resonator Antennas one need to know the er and the dielectric loss to estimate the resonant frequency. An indirect method is proposed in this letter to find the er from Transversely Misaligned Dual-Fiber Optical Trapping at the optical frequency range to approximately estimate {\epsilon}r and thereby understand the correlation between these two regimes of frequency responses.

physics.optics↗

arXiv2025

Estimating the Diffuseness for the Non-Relaxor Type Ferroelectric to Paraelectric Phase Transition in BaTiO3

The normal ferroelectric to paraelectric phase transition in model ferroelectric materials such as BaTiO3 is typically characterized by a sharp, well-defined dielectric constant peak at a specific transition temperature. However, under certain modifications of the parent material, this transition can become diffuse over a broad range of temperatures. This has garnered significant research attention over the past few decades, primarily because of its intriguing and not yet fully understood physical properties. The parameters developed to measure the diffuseness are also ambiguous. In this work, an investigation has been conducted to understand the transition dynamics of the non-relaxor ferroelectric systems in the temperature interval over which the diffuse phase transition occurs. This is achieved by modelling the dielectric response phenomenologically, using a distribution of local transition temperatures. Moreover, a temperature dependent differential analysis is introduced, enabling the clear demarcation of distinct dielectric regimes and providing enhanced insight into the evolution of the phase transition. It is strongly recommended that the degree of diffuseness is skeptical in many senses. Hence, following the establishment, a simple yet effective new measure of diffuseness is being proposed, offering a more accurate and physically meaningful estimation of the diffuse phase transition.

cond-mat.mtrl-sci↗

arXiv2025

Correlation of the role of Li-doping in control of O-vacancies and Li interstitial formations in NiO with electrochemical properties

Aliovalent doping in an oxide material introduces modifications in the valence state of the host cation and often leads to tailoring the oxygen content in the lattice. Moreover, if the dopant cation is larger than the host cation, the lattice strain and disorder may be affected. Such changes are expected to modify the electronic clouds and lead to different ligand fields, which in turn should modify the bond lengths, and therefore phonons, electronic properties, transport properties, and charge storage properties. To understand such correlations an example is being investigated in this study by doping a larger Li+ ion in a NiO lattice. The effect on structure, phonons, electronic properties, and charge storage properties are investigated and correlated in a first-of-its-kind report. The charge storage properties are observed to improve with Li+ doping until 3% substitution and thereafter decrease due to the generation of Li+ interstitial in a 6% incorporated sample. The connection of oxygen vacancies and Ni3+ formation with Li+ incorporation is the backbone of this report.

cond-mat.mtrl-sci↗

arXiv2024

Enhancing Fenton-like Photo-degradation and Electrocatalytic Oxygen Evolution Reaction (OER) in Fe-doped Copper Oxide (CuO) Catalysts

Although hydrogen generation by water electrolysis is the cheapest of all other available sources, water splitting still occurs with sluggish kinetics. It is a challenging barrier for H2 production on a large scale. Moreover, research is still underway to understand the oxygen evolution reaction (OER) and design the catalysts with improved OER performance. Herein, we report the synthesis, characterization, and OER performance of iron-doped copper oxide (CuO) as low-cost catalysts for water oxidation. The OER occurs at about 1.49 V versus the RHE with a Tafel slope of 69 mV/dec in a 1 M KOH solution. The overpotential of 338 mV at 10 mA/cm2 is among the lowest compared with other copper-based materials. The catalyst can deliver a stable current density of >10 mA/cm2 for more than 10 hours. Additionally, wastewater treatment, particularly synthetic dye wastewater, is vital for preventing water scarcity and adverse effects on human health and ecotoxicology. The as-synthesized catalysts are also utilized for Fenton-like photo-degradation under low-power visible household LED lights toward the most commonly industrially used simulated Methylene blue dye wastewater. Almost complete degradation of the MB dye has been achieved within 50 minutes of visible light irradiation with a first-order rate constant of 0.0973/min. This dual functionality feature can open new pathways as a non-noble, highly efficient, and robust catalyst for OER and wastewater treatments.

physics.app-ph↗

arXiv2024

Recent advances in hydrogen production using sulfide-based photocatalysts

Sulfide-based photocatalysts (PC) are promising materials for efficiently producing hydrogen (H2). This chapter aims to provide a detailed survey of the recent advancements in sulfide-based photocatalysts and emphasize their enhanced performance and pathways to efficient H2 production. A detailed summary has been given, including several metal sulfides, such as cadmium sulfide (CdS), zinc sulfide (ZnS), molybdenum disulfide (MoS2), tungsten disulfide (WS2), lead sulfide (PbS), nickel sulfides (NiS/NiS2), iron disulfide (FeS2), copper sulfides (CuS/Cu2S), cobalt sulfides (CoS/CoS2), tin disulfide (SnS2), indium sulfide (In2S3), bismuth sulfide (Bi2S3), zinc cadmium sulfide (ZnxCd1-xS), manganese cadmium sulfide (MnxCd1-xS), zinc indium sulfide (ZnIn2S4), and cadmium indium sulfide (CdIn2S4). This chapter will focus on the latest advancements in metal-sulfide-based materials for photocatalytic hydrogen evolution reactions (HER), taking its accelerated growth and excellent research into account. After briefly outlining the basic properties, the chapter will showcase the cutting-edge strategies and recent research progress, including the construction of heterojunctions, defect engineering, co-catalyst loading, elemental doping, and single-atom engineering, which improve the electronic structure and charge separation capabilities of metal sulfides for photocatalytic hydrogen production. A future perspective and outlook have been proposed, focusing on some key points and a standard protocol. With this knowledge, we hope sulfide-based photocatalysts can be modified and engineered to improve their efficiency and stability in future research.

cond-mat.mtrl-sci↗

arXiv2024

Effect of pH on photocatalytic degradation of Methylene Blue in water by facile hydrothermally grown TiO2 Nanoparticles under Natural Sunlight

Each year, the production of synthetic dye wastewater reaches a trillion tons, posing a significant challenge to addressing water scarcity on a global level. Hence, the treatment of wastewater to prevent water scarcity is of prime importance, and failing to do so will increase ecotoxicological risks and human health. Textile wastewater contains harmful dye. Photocatalytic degradation of such dye-contaminated wastewater is crucial to purifying the dye-contaminated water. However, this process takes time, uses high-power lamps, and is expensive. Here, we report the effect of the concentration of precursor on the size and surface morphology of TiO2 nanostructures prepared by facile hydrothermal synthesis and its ability to perform as a photocatalyst to degrade the most common industrial textile dye, methylene blue (MB), under natural sunlight. The impact of particle size on the photocatalytic activity and photocarrier migration rate was thoroughly examined. Also, the effect of pH on adsorption and photocatalytic degradation has been evaluated in detail. With several optimized conditions, almost complete dye degradation was achieved within 40 minutes under the direct illumination of natural sunlight. The enhanced photocatalytic performance can be correlated to the synergetic effect of a higher charge transfer mechanism, good catalytic active surface area availability (386 m2/g), and several optimized parameters that affect the reaction efficacy. Additionally, repeated use of NPs without sacrificing performance five times confirmed its stability and Sustainability as a promising candidate for large-scale industrial textile wastewater remedies.

cond-mat.mtrl-sci↗

arXiv2024

Room temperature ferromagnetism induced by high valence cation V$^{+5}$/V$^{+4}$ substitution in SrFeO$_{3-\delta}$

The structural and magnetic effects of non-magnetic vanadium (V) doping in helimagnetic SrFeO$_{3-\delta}$ (SFO) are investigated, focusing on up to 3% substitution at the Fe site. Structural analysis from X-ray diffraction (XRD) and Raman spectroscopy, supported by phonon mode calculations, reveals that pure SFO exists as a mixed tetragonal-orthorhombic phase, while V-doped samples exhibit an emerging cubic phase alongside tetragonal symmetry. Magnetic hysteresis (M-H) loops show notable ferromagnetic behavior within the antiferromagnetic matrix, persisting even at room temperature. Temperature-dependent magnetization measurements indicate a Neel temperature (TN ) shift from 70K to 55K, along with increased magnetization differences in field-cooled (FC) and zero field-cooled (ZFC) data, reflecting heightened magnetic frustration due to competing FM/AFM exchange interactions. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) analyses reveal a rise in Fe$^{3+}$ and V$^{5+}$ states, affecting oxygen vacancy distributions and corresponding structural shifts seen in XRD and Raman results. The multivalent Fe$^{3+}$/Fe$^{4+}$ and V$^{4+}$/V$^{5+}$ states enhance double-exchange (DE) and super-exchange (SE) interactions (Fe$^{3+}$-O-Fe$^{4+}$ and Fe$^{3+}$-O-V$^{5+}$), promoting ferromagnetism. Frequency-dependent magnetization studies display a subtle susceptibility peak shift, indicating spin-glass-like behavior in V-doped samples.

cond-mat.mtrl-sci↗

arXiv2024

Room temperature Multiferroicity and Magnetoelectric coupling in Ca/Mn modified BaTiO3

Materials with magnetoelectric coupling (MEC) between ferroic orders at room temperature are emerging field in modern technology and physics. BaTiO3 is a robust ferroelectric in which several doping has led to MEC. In Ca and Mn modified BaTiO3 has been study with a series of Ba(1-x)Ca(x)Ti(1-y)Mn(y)O3 (x=y= 0, 0.03, 0.06, 0.09), in this MEC was only observed in x=0.03. The structural modifications with changing substitution reveal a reduced Ti-O-Ti bond angle for this sample which is the most ferromagnetic in nature. A mixed phase of tetragonal P4mm and hexagonal P63/mmc space groups of BaTiO3 is observed in the substituted samples, with nominal contribution of the hexagonal phase for x=0.03. A valence state study using XPS and XANES reveals the presence of enhanced proportion of Mn3+ ions in the sample which support a pseudo Jahn-Teller distortion, thereby supporting the ferroelectricity for x=0.03. Direct evidences of MEC was obtained from magnetoelectric measurements. A magnetoelectric coupling coefficient, {\alpha}ME ~44 mVcm-1Oe-1 was obtained for dc magnetic field of 600 Oe and a 10Hz ac field of 40 Oe. Such MEC was not observed for higher substitution which emphasizes the sensitivity of the structural properties on substitution.

cond-mat.mtrl-sci↗

arXiv2024

Unveiling the Direct Piezoelectric Effect on Piezo-phototronic Coupling in Ferroelectrics: First Principle Study Assisted Experimental Approach

A new study explores the distinct roles of spontaneous polarization and piezoelectric polarization in piezo-phototronic coupling. This investigation focuses on differences in photocatalytic and piezo-photocatalytic performance using sodium bismuth titanate (NBT), a key ferroelectric material. The research aims to identify which type of polarization has a greater influence on piezo-phototronic effects. A theoretical assessment complements the experimental findings, providing additional insights. This study explores the enhanced piezo-phototronic performance of electrospun nanofibers compared to sol-gel particles under different illumination conditions (11W UV, 250W UV, and natural sunlight). Electrospun nanofibers exhibited a rate constant (k) improvement of 2.5 to 3.75 times, whereas sol-gel particles showed only 1.3 to 1.4 times higher performance when ultrasonication was added to photocatalysis. Analysis using first-principle methods revealed that nanofibers had an elastic modulus (C33) about 2.15 times lower than sol-gel particles, indicating greater flexibility. The elongation of lattice along z-axis in the case of nanofibers reduced the covalency in the Bi-O and Ti-O bonds. These structural differences led to reduced spontaneous polarization and piezoelectric stress coefficients (e31 & e33). Despite having lower piezoelectric stress coefficients, higher flexibility in nanofibers led to a higher piezoelectric strain coefficient, 2.66 and 1.97 times greater than sol-gel particles, respectively. This improved the piezo-phototronic coupling for nanofibers.

cond-mat.mtrl-sci↗

arXiv2024

Investigation of BaTiO$_3$-NiO composite as compact Dielectric Resonator Antenna

A compact dielectric resonator antenna has been fabricated on a microstrip transmission line for the purpose of C-band wireless communication using a ceramic material made out of a sintered mixture of BTO and NiO. The antenna parameters are optimized using Ansys HFSS software and verified experimentally. Ni replaces both Ba at A site and Ti at B site. Such a solid solution has a limit depending on the amount of NiO provided during sintering. A complete study of the structural changes and the dielectric constant enables the correlation with the resonating property. All the samples retain the ferroelectric tetragonal P4mm phase with a nominal decrease in the c/a ratio. NiO incorporation in BTO decreases the sintering temperature and shows two types of morphology associated with BTO-like and NiO-like phases. It induces prominent reduction in the permittivity and loss tangent (<0.01) in the range 100Hz to 1MHz. These properties make these samples suitable for DRA application in the C-Band range [4-8 GHz]. Experimental and theoretical assessment using HFSS software yields a C-band signal at ~7.27 GHz.

physics.app-ph↗

arXiv2023

Recent advances in La2NiMnO6 Double Perovskites for various applications; Challenges and opportunities

Double perovskites R2NiMnO6 (R= Rare earth element) (RNMO) are a significant class of materials owing to their Multifunctional properties with structural modifications. In particular, multifunctional double perovskite oxides La2NiMnO6 (LNMO) which possess both electric and magnetic orderings, chemical flexibility, versatility, and indispensable properties like high ferromagnetic curie temperature, high absorption rates, dielectrics, etc. have drawn a lot of attention due their rich physics and diverse applications in various technology. This justifies the intense research in this class of materials, and the keen interest they are subject to both the fundamental and practical side. In view of the demands of this material in lead-free perovskite solar cells, photocatalytic degradation of organic dyes, clean hydrogen production, electric tuneable devices, Fuel cells, gas sensing, and Biomedical applications, there is a need for an overview of all the literature so far, the ongoing research and the future prospective. This review summarised all the Physical and Structural Properties of LNMO such as electric, magnetic, catalytic, and dielectric properties with their underlying mechanisms. This review article provides insight into the scope of studies in LNMO material for exploring unexposed properties in new material research and to identify areas of future investigation of the materials in the double perovskite family.

cond-mat.mtrl-sci↗

arXiv2023

Effect of pH on structure and surface charge of Fe$_2$O$_3$ nanoparticles synthesized at different pH conditions and correlation to antibacterial properties

pH of a solution is the ratio of H+/OH- ions. The relative ratio of these charges may affect forming bonds during a hydrothermal synthesis by influencing electronic clouds of participant ions, which can modify the structure and hence crystallinity, strain, disorder, surface termination etc. These factors may modify physical properties including the surface charge. This work uses hematite nanoparticles to correlate the structural modifications to all these properties and finally to the antibacterial properties due to the surface charge interaction of the nanoparticles and the bacterial cell walls.

cond-mat.mtrl-sci↗

arXiv2022

Room Temperature Magneto-dielectric coupling in the CaMnO3 modified NBT lead-free ceramics

The sol-gel prepared (1-x) Na0.5Bi0.5TiO3- (x) CaMnO3 (x=0, 0.03, 0.06, 0.12) compositions show a Rhombohedral (R3c) phase for x=0.06 while a mixed Rhombohedral (R3c) and orthorhombic (Pnma) phases for the x=0.12. The lattice volume consistently decreased with an increase in the CaMnO3 content. The phase transition temperature (Tc) decreased with an increase in the CaMnO3 compositions. The room temperature dielectric constant increased, and loss decreased for the x=0.03 composition due to a decrease in the oxygen vacancy and Bi loss confirmed by the valence state study (XPS). All the compositions show a variation of the room temperature dielectric property with an application of magnetic field confirming a magnetodielectric coupling. The x=0.06 composition shows the highest negative magnetodielectric constant (MD%) of 3.69 at 100kHz at an applied field of 5 kG.

cond-mat.mtrl-sci↗

arXiv2021

Defect Dipole Induced Improved Electrocaloric Effect in Modified NBT-6BT Lead-Free Ceramics

The Rietveld refinement of the polycrystalline powders of 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at the Ti-site confirmed a single rhombohedral (R3c) phase. The bandgap, (Eg) was affected by the anti-phase octahedral tilt angle and the spin-orbit splitting energy of Ti4+2p3/2 and Ti4+2p1/2 states. The decrease in Bi loss and increase in the binding energy of Ba due to Fe/Mn doping has been correlated to the strengthening of Bi-O and Ba-O bonds which was revealed from the XPS studies thereby further related to the average A-O bond length from structural studies. Hence, a reduction of oxygen vacancy (VO) for the doped samples has been justified. A significant improvement of the dielectric constant, relaxation time (τ0), and the decrease in conductivity due to doping was revealed from the frequency-dependent (10Hz-1MHz) dielectric measurement study. The conduction and relaxation process is dominated by the short-range movement of defects. The activation energy (Ea ~1eV) revealed that there is a presence of double-ionized VOs. The ECE study showed a significant enhancement of the changes in entropy, and the adiabatic temperature difference due to doping, with the change in tempearture being highest in the Fe-doped sample. Such improvement of dielectric and ECE properties was confirmed due to the reduction of the mobility of oxygen vacancy because of the formation defect dipoles.

cond-mat.mtrl-sci↗