arXiv subjects

Ambesh Dixit

Publications and source records attributed to Ambesh Dixit.

At least 19 recordsLinked to original sources

arXiv2026

Photovoltaic Possibility of Cu2SiSe3 and Cu2SnS3 Ternary Chalcogenides- Single Junction to Tandem Architecture

Cu based ternary chalcogenides are gathering attention for sustainable energy applications due to their reduced complexity compared to quaternary alternatives. We used drift diffusion modeling to evaluate the feasibility of photovoltaics employing ternary chalcogenide absorbers based on Cu2SiSe3 and Cu2SnS3. The device metrics are evaluated by analyzing absorber layer thickness intrinsic carrier concentration defect density and energy band alignment at interfacial junctions. The optimized single junction Cu2SiSe3 based device configuration achieves a power conversion efficiency of 18.13 percent exhibiting a short circuit current density of 38 mA cm^-2 and an open circuit voltage of 0.64 V. The Cu2SnS3 based device achieves an efficiency of 15.59 percent with a short circuit current density of 48.8 mA cm^-2 and an open circuit voltage of 0.42 V. We examined the impact of the buffer layer on device parameters uncovering further avenues for performance improvement. Additionally we simulated a two terminal tandem solar cell using Cu2SiSe3 Eg 1.44 eV in the upper cell to capture photons from the visible spectrum and Cu2SnS3 Eg 0.91 eV in the lower cell to absorb from the infrared spectrum. The simulated tandem architecture, featuring a VOC of 1.24 V a JSC of 24.6 mA cm^-2 a fill factor (FF) of 79.2 percent and an efficiency of 24.1 percent markedly surpassed conventional single junction devices demonstrating the viability of Cu2SiSe3-Cu2SnS3 absorber-based tandem solar cells for next generation high-efficiency solar technologies.

cond-mat.mtrl-sci↗

arXiv2026

Distorted polyhedral architecture enabled high thermoelectric performance of columnar double halide perovskites Cs2AgPdCl5 and Cs2AgPtCl5

We investigate the thermoelectric properties of two newly synthesized columnar double halide perovskites Cs$_2$AgPdCl$_5$ and Cs$_2$AgPtCl$_5$. These materials accommodate a distorted local polyhedral architecture with tetrahedral symmetry compared to traditional double halide perovskites. By employing density functional theory along with the semiclassical transport model, we have analyzed the electronic and transport properties of these materials. Our results show that at 800 K, the largest figure of merit ($zT$) is 1.30 (0.86) for p-type (n-type) Cs$_2$AgPdCl$_5$ and 0.87 for n-type Cs$_2$AgPtCl$_5$ at doping concentrations of $1.94 \times 10^{20}$ ($3.76 \times 10^{19}$) cm$^{-3}$ and $3.52 \times 10^{19}$ cm$^{-3}$, respectively. Remarkably, a very low doping concentration is required to achieve a high $zT$, setting these materials apart from others in this field. Our calculations demonstrate that Cs$_2$AgPdCl$_5$ benefits from the presence of conduction and valence band valleys near the band edges; however, the flat bands present in the valence band of Cs$_2$AgPtCl$_5$ do not improve its thermoelectric performance. Among these systems, hole doping in Cs$_2$AgPdCl$_5$ has shown remarkable thermoelectric performance. Interestingly, the local octahedral distortions present in these perovskites contribute to a marked reduction in the lattice thermal conductivity to 0.27 W/mK in Cs$_2$AgPtCl$_5$ and 0.20 W/mK in Cs$_2$AgPdCl$_5$ by causing enhanced phonon scattering, further improving the thermoelectric figure of merit. This drop in thermal conductivity, combined with the favorable electronic properties, underscores the potential use of these materials for applications in highly efficient thermoelectric devices.

cond-mat.mtrl-sci↗

arXiv2026

Synergistic effect of the electronic band delocalization and bond anharmonicity on the thermoelectric performance of Cs2TeX6(X=Cl, Br, I)

We investigate the structural, mechanical, and thermoelectric properties of lead-free double halide perovskites Cs2TeX6 (X = Cl, Br, I) using first-principles calculations and semiclassical Boltzmann transport theory. The HSE06 band gap is incorporated using the scissor correction method along with PBE calculated electronic band structures including spin orbit coupling to accurately predict transport properties. The band gap values are 3.27, 2.50, and 1.55 eV for Cs2TeX6 (X = Cl, Br, I), respectively. The coexistence of heavy and light bands in the Cs2TeI6 band structure helps mitigate the trade-off between the Seebeck coefficient and electrical conductivity. Among these systems, Cs2TeI6 exhibits superior performance with a ZT of 1.97 at 800 K and an electronic concentration of 3.35 x 10^19 cm^-3. Such a high ZT at relatively low carrier concentration arises from high electrical conductivity combined with low lattice thermal conductivity. The lattice thermal conductivity of Cs2TeI6 is found to be 0.41 W m^-1 K^-1 at room temperature. This low lattice thermal conductivity is attributed to weak Te-I bonding and non-uniform out-of-phase displacement of Cs atoms. The presence of local TeX6 units together with weak bonds strongly resists heat conduction, leading to significant suppression of lattice thermal conductivity. In particular, transverse acoustic phonons and optical phonons play a key role in limiting lattice thermal conductivity. These results identify Cs2TeI6 as a promising candidate for high performance thermoelectric applications.

cond-mat.mtrl-sci↗

arXiv2026

Non-Enzymatic Glucose sensing properties of NiO nanostructured flower decorated Exfoliated Graphite Electrodes

Nanostructured transition metal oxides (TMO) are extensively explored materials for non-enzymatic glucose sensors. TMOs such as Iron oxides( {\alpha}-Fe2O3, {\gamma}-Fe2O3, Fe3O4, etc.), NiO, CuO, Cr2O3, etc. have been utilized as electrocatalysts for glucose determination. Tremendous efforts have been put into identifying the impact of different morphologies of these materials on the glucose-sensing performance. The larger surface area of the flower and wire-shaped catalysts make them better performing amongst other morphologies. Interestingly, it is important to note that most of such studies are on standard Glassy Carbon electrodes. Further to enhance the Electrochemically active surface area (ECSA) of the electrode, Carbon nanomaterials such as reduced Graphene Oxide (r-GO) and Carbon Nanotubes (CNTs) are used as additives. Exfoliated Graphite paper electrodes offer better electrochemical characteristics than GCE electrodes due to their much larger ECSA. This study presents the non-enzymatic glucose sensing properties of NiO nanoflower-decorated Exfoliated Graphite electrodes. The amperometric detection of glucose shows a linear increase in current over a physiologically relevant wide range of 0-10 mM. The electrodes offer a better sensitivity of 304.12 microA per mM per cm square and a Limit Of Detection (LOD) of 100 microM. In addition, the electrodes showed high selectivity towards glucose in the presence of other interfering species such as Ascorbic acid, Fructose, Sucrose, and NaCl.

cond-mat.mtrl-sci↗

arXiv2025

Crystal Systems Classification of Phosphate-Based Cathode Materials Using Machine Learning for Lithium-Ion Battery

The physical and chemical characteristics of cathodes used in batteries are derived from the lithium-ion phosphate cathodes crystalline arrangement, which is pivotal to the overall battery performance. Therefore, the correct prediction of the crystal system is essential to estimate the properties of cathodes. This study applies machine learning classification algorithms for predicting the crystal systems, namely monoclinic, orthorhombic, and triclinic, related to Li P (Mn, Fe, Co, Ni, V) O based Phosphate cathodes. The data used in this work is extracted from the Materials Project. Feature evaluation showed that cathode properties depend on the crystal structure, and optimized classification strategies lead to better predictability. Ensemble machine learning algorithms such as Random Forest, Extremely Randomized Trees, and Gradient Boosting Machines have demonstrated the best predictive capabilities for crystal systems in the Monte Carlo cross-validation test. Additionally, sequential forward selection (SFS) is performed to identify the most critical features influencing the prediction accuracy for different machine learning models, with Volume, Band gap, and Sites as input features ensemble machine learning algorithms such as Random Forest (80.69%), Extremely Randomized Tree (78.96%), and Gradient Boosting Machine (80.40%) approaches lead to the maximum accuracy towards crystallographic classification with stability and the predicted materials can be the potential cathode materials for lithium ion batteries.

cond-mat.mtrl-sci↗

arXiv2025

Investigation of electronic energy levels in a weak ferromagnetic oxygen-deficient BiFeO2.85 thick film using absorption and X ray photoelectron spectroscopic studies

We grew a 2 micron thick film of single-phase BiFeO3 on a Si (100) substrate by pulsed laser deposition with a substrate temperature of 575 oC and an oxygen partial pressure of 0.06 mbar. X ray diffraction analysis indicated that the film exhibits textured growth along the (110) plane and possesses a rhombohedral R3c structure. Investigations using scanning electron microscopy and atomic force microscopy revealed an average grain size of about 300 nm and a surface roughness of 18 nm for the film. Energy dispersive X ray analysis estimated the composition of the film to be BiFeO2.85. Temperature- and magnetic field dependent magnetization measurements demonstrated weak ferromagnetic properties in the BiFeO2.85 film, with a non-zero spontaneous magnetization at H = 0 Oe across the temperature range of 2 to 300 K. Furthermore, the exchange bias field (HEB) of the film changed from the positive exchange bias field (+HEB = +6.45 Oe) at 200 K to a negative field (-HEB = -8.12 Oe) at 100 K, indicating a shift in macroscopic magnetism from antiferromagnetic to weak ferromagnetic order below 200 K. Elemental analysis via X-ray photoelectron spectroscopy revealed that the Fe ions in the BiFeO2.85 film are in a 3+ valence state, and a peak feature at 532.1 eV confirmed the presence of induced oxygen vacancies. UV visible NIR and valence band spectroscopic studies showed that the direct band-gap energy, and the separation between the valence band maximum and Fermi energy were approximately 2.27 eV and 0.9 eV, respectively, which are red-shifted when compared to its bulk form.

cond-mat.mtrl-sci↗

arXiv2025

Probing electronic transitions and defect-induced Urbach tail bands in functional perovskite oxides using diffuse reflectance

We conducted a detailed study of electronic transitions and defects induced Urbach tail bands in various functional perovskite oxides (V2O5, BaSnO3, PbZr0.52Ti0.48O3, BiMnO3, and BiFeO3) using diffuse reflectance spectroscopy (DRS). We analyzed their DRS spectra using the Kubelka-Munk (KM) function, the Tauc plot, and the first derivative of the reflectance for a comparative study. BiMnO3 exhibits an electronic transition with indirect band gap energy, Eg = 0.92 eV. In contrast, all other functional perovskite oxides, namely bulk V2O5, BaSnO3, PbZr0.52Ti0.48O3, and BiFeO3, show direct band gap interband transitions, with Eg values of 2.27, 3.25, 3.10, and 2.48 eV, respectively. The estimated Urbach energy (EU) values related to the induced defects in these direct band gap functional oxides are approximately 0.24, 0.38, 0.25, and 0.48 eV, respectively. Moreover, a reduction in the band gap energy of multiferroic BiFeO3 was observed due to induced chemical pressure from (Ba, Ca) doping and a decrease in particle size. Importantly, the evaluated band gap and Urbach energies of the functional perovskite oxide materials obtained from the analyses of the first derivative of reflectance and the Tauc plot method align remarkably well with the values deduced using the Kubelka-Munk function theory. Effectively, we propose a comprehensive electronic band structure for the multiferroic BiFeO3, an important material for optoelectronic applications such as photovoltaic, photocatalytic, and photoferroelectric devices.

cond-mat.mtrl-sci↗

arXiv2025

Entropy measures and their applications: A comprehensive review

Entropy has emerged as a dynamic, interdisciplinary, and widely accepted quantitative measure of uncertainty across different disciplines. A unified understanding of entropy measures, supported by a detailed review of their theoretical foundations and practical applications, is crucial to advance research across disciplines. This review article provides motivation, fundamental properties, and constraints of various entropy measures. These measures are categorized with time evolution ranging from Shannon entropy generalizations, distribution function theory, fuzzy theory, fractional calculus to graph theory, all explained in a simplified and accessible manner. These entropy measures are selected on the basis of their usability, with descriptions arranged chronologically. We have further discussed the applicability of these measures across different domains, including thermodynamics, communication theory, financial engineering, categorical data, artificial intelligence, signal processing, and chemical and biological systems, highlighting their multifaceted roles. A number of examples are included to demonstrate the prominence of specific measures in terms of their applicability. The article also focuses on entropy-based applications in different disciplines, emphasizing openly accessible resources. Furthermore, this article emphasizes the applicability of various entropy measures in the field of finance. The article may provide a good insight to the researchers and experts working to quantify uncertainties, along with potential future directions.

math.PR↗

arXiv2024

Estimation of Tsallis entropy for exponentially distributed several populations

We study the estimation of Tsallis entropy of a finite number of independent populations, each following an exponential distribution with the same scale parameter and distinct location parameters for $q>0$. We derive a Stein-type improved estimate, establishing the inadmissibility of the best affine equivariant estimate of the parameter function. A class of smooth estimates utilizing the Brewster technique is obtained, resulting in a significant improvement in the risk value. We computed the Brewster-Zidek estimates for both one and two populations, to illustrate the comparison with best affine equivariant and Stein-type estimates. We further derive that the Bayesian estimate, employing an inverse gamma prior, which takes the best affine equivariant estimate as a particular case. We provide a numerical illustration utilizing simulated samples for a single population. The purpose is to demonstrate the impact of sample size, location parameter, and entropic index on the estimates.

math.ST↗

arXiv2023

Impact of Cr-O hyrbidization in ACrO3 (A=La, Y): A Theoretical Investigation

Electronic properties of spin polarized antiferromagnetic ACrO3 (A = La, Y) are explored with Hubbard Model using Density Functional Theory (DFT). These two isostructural systems are investigated using the different Hubbard energy and analyzed the hybridization of chromium 3d orbitals and oxygen 2p orbitals and the change in energy band gaps against the Hubbard energy. The bond length and bond angle affect significantly the orbital contributions of Cr-3d and O-2p electrons for both the system. We noticed that the Cr-O hybridization affects the orbital degeneracy and is substantiated with partial density of states. These results emphasize the contribution of Hubbard energy in correlated electron systems.

cond-mat.mtrl-sci↗

arXiv2021

Room Temperature Structural, Magnetic and Dielectric Characteristics of La Doped CuO Bulk Multiferroic

In this manuscript, we report room temperature structural, microstructural, optical, dielectric, and magnetic properties of CuO and Cu0.995La0.005 ceramics, synthesized by solid-state reaction method. La doping in CuO leads to the evolution of compact and dense microstructure with reduced porosity. Due to noticeable differences in the ionic radii of, La doping creates vacancy defects which induce considerable strain in the CuO lattice resulting in a reduction in the lattice parameters and cell volume. However, both ceramics processes a similar monoclinic structure with the C2/c space group. Detailed characterization using XPS, Raman, and FTIR spectroscopy confirmed the incorporation of the La3+ in CuO lattice. Interestingly, La doping enhances the dielectric constant by more than three times and results in a reduced leakage current. The onset of a large dielectric constant is attributed to dense microstructure and strain/distortion in CuO lattice after La doping. Additionally, the band-gap of Cu0.995La0.005 ceramics decreases which is attributed to increased vacancy defect concentration that creates intermediate dopant energy level within bandgap of CuO matrix. Furthermore, improvement in magnetic and dielectric properties is also discussed and correlated with the grain size in La-doped CuO.

cond-mat.mtrl-sci↗

arXiv2021

Low temperature magnetic and dielectric properties correlation in Fe-doped copper (ii) oxide ceramics for potential device application

The bulk samples of CuO and Fe-doped CuO were synthesized by ceramics methods. Structural and compositional analyses were performed by using X-ray diffraction, SEM, and EDAX. Through this manuscript, we are going to report the effect of trivalent iron doping (Fe$^{3+}$) in copper (II) oxide (Cu$_{0.95}$Fe$_{0.05}$O) bulk samples on magnetic and dielectric behavior. The paramagnetic phase has been established in CuO as a result of Fe$^{3+}$ doping. The strong correlation between magnetic and dielectric properties indicated spin-polaron interaction at the transition temperature. Bulk CuO and also Cu$_{0.95}$Fe$_{0.05}$O exhibit the multiferroic phase in a narrow temperature range (190 K to 230 K). Two transitions happened from a paramagnetic-paraelectric phase to incommensurate or asymmetrical antiferromagnetic (AF) and ferroelectric state near highest Neel temperature (TN1) ~230 K and another second phase transition, the order of AF phase transformed to commensurate AF phase and ferroelectricity disappeared at around the Neel temperature (TN2) ~210 K in all samples. This Cu$_{0.95}$Fe$_{0.05}$O would show its potential in the spintronic application for a high dielectric constant with low loss and high magnetic susceptibility.

cond-mat.mtrl-sci↗

arXiv2020

Cathode Materials for Lithium Ion Batteries (LIBs): A Review on Materials related aspects towards High Energy Density LIBs

This article reviews the development of cathode materials for secondary lithium ion batteries since its inception with the introduction of lithium cobalt oxide in early 1980s. The time has passed and numerous cathode materials are designed and developed to realize not only the enhanced capacity but also the power density simultaneously. However, there are numerous challenges such as the cyclic stability of cathode materials, their structural and thermal stability, higher operating voltage together with high ionic and electronic conductivity for efficient ion and charge transport during charging and discharging. This article will cover the development of materials in chronological order classifying as the lithium ion cathode materials in different generations. The ternary oxides such as LiTMOx (TM=Transition Metal) are considered as the first generation materials, whereas modified ternary and quaternary oxide systems are considered as the second generation materials. The current i.e. third generation includes complex oxide systems with higher lithium content such as Li2TMSiO4 aiming for higher energy density. Further, developments are heading towards lithium metal based batteries with a possibility for very high energy densities.

cond-mat.mtrl-sci↗

arXiv2019

Anomalous magnetic behavior and complex magnetic structure of proximate LaCrO3 LaFeO3 system

We investigated complex magnetic properties of multifunctional LaCrO3-LaFeO3 system. The magnetic measurements substantiate the presence of competing complex magnetic ordering against temperature, showing paramagnetic to ferrimagnetic transition at 300 K, followed by antiferromagnetic (AFM) transition near 250 K superimposed on ferrimagnetic phase. The onset of weak ferrimagnetic ordering is attributed to the competing complex interaction between two AFM LaCrO3-LaFeO3 sublattices. The low-temperature AFM ordering is also substantiated by temperature-dependent Raman measurements, where the intensity ratio of 700 cm-1 Raman active mode showed the clear enhancement with lowering the temperature. The non-saturating nature of magnetic moments in LaCrO3-LaFeO6 suggests the predominating AFM ordering in conjunction with ferrimagnetic ordering between 250 K to 300 K up to 5 T magnetic field. A complex magnetic structure of LaCrO3-LaFeO3 is constructed, emphasizing the metastable magnetic phase near room temperature and low temperature antiferromagnetic state.

cond-mat.str-el↗

arXiv2019

Magnetic Entropy in a Non-Collinear Weak Ferromagnetic YCrO3

We carried out temperature and field dependent magnetic measurements to understand the evolution of magnetic non-collinearity near antiferromagnetic phase in conjunction with the evolution of magnetic entropy near phase transition. We observed the maximum change in entropy just before magnetic ordering of Cr3+ in YCrO3 with the maximum change in magnetic entropy of -0.38 Jkg-1K-1 at 8 Tesla external field. The data is linear in higher fields 3 T - 8 T , whereas it showed deviations in the lower field region. The maximum entropy change fits well with mean field approximation at higher fields, while the observed deviation in lower field substantiates the onset of weak ferromagnetism in YCrO3.

cond-mat.str-el↗

arXiv2019

Neutron Diffraction Studies on Temperature Driven Crystallographic Anisotropy in FeVO4 Multiferroic: Evidence of Strong Magnetostructural Correlations

We used temperature-dependent neutron diffraction measurements on FeVO4 to understand the temperature driven anisotropy and observed that the maximum change for a and b lattice parameters in conjunction with a large contraction in angle β as a function of temperature. The least changes are observed for the c lattice parameter and in γ angle. From these structural parameters, it can be said that, FeVO4 exhibits large structural anisotropy with lowering temperature. The large change in lattice parameters in magnetic phases i.e. below 22 K explains the strong magnetostructural coupling in FeVO4.

cond-mat.mtrl-sci↗

arXiv2018

MoSSe Janus monolayer as a promising two dimensional material for NO2 and NO gas sensor applications

Gas sensing mechanism of H2S, NH3, NO2 and NO toxic gases on transition metal dichalcogenides based Janus MoSSe monolayers are investigated using the density functional theory. The pristine and defect included MoSSe layers are considered as a host material for adsorption study. Three types of defects (i) molybdenum vacancy, (ii) selenium vacancy, and (iii) sulfur/selenium vacancy are studied to understand their impact on electronic properties and sensing of these gas molecules. The formation energy is computed to predict the stability of these defects and noticed that selenium vacancy is the most stable among other defects. The adsorption of gas molecules is evaluated in terms of adsorption energy, vertical height, charge difference density, Bader charge analysis, electronic and magnetic properties. The maximum adsorption energy for H2S, NH3, NO2 and NO molecules on pristine Janus MoSSe monolayer are ~ -0.156eV, -0.203eV, -0.252eV, and -0.117eV, respectively. Selenium and sulfur/selenium defects significantly improve the sensing of the gas molecules. NO2 gas molecule dissociates and forms oxygen doped NO adsorption in selenium and sulfur/selenium defect included MoSSe Janus monolayer. The adsorption energy values are ~ -3.360eV and -3.404eV for Se and S/Se defects included MoSSe layer, respectively. Further, the adsorption of NO2 molecule induced about 1/mu/B magnetic moment. In contrast, NO molecule showed chemisorption on the surface of the selenium and sulfur/selenium defect included Janus MoSSe monolayers, whereas H2S and NH3 molecules showed physisorption with their adsorption energies in the range of -0.146 to -0.238 eV and -0.140 to -0.281 eV, respectively. The adsorption of H2S, NH3, NO2 and NO molecule on the pristine and defected monolayers suggest that selenium and sulfur/selenium vacancy defects are more prominent for NO2 and NO gas molecule adsorption.

cond-mat.mtrl-sci↗

arXiv2018

Impact of excess and disordered Sn sites on Cu2ZnSnS4 absorber material and device performance: A 119Sn Mossbauer Study

Mossbauer analysis is carried out on CZTS samples, subjected to a low temperature processing at 3000C (S1) and high temperature processing at 5500C under sulfur environment (S2). Loss of Sn is observed in sample S2 due to high temperature thermal treatment.The isomer shifts obtained in the Mossbauer spectra confirms the existence of Sn at its 4+ valance state in both the samples. Relatively high quadriple splitting is observed in S1 with respect to S2, suggesting dislocations and crystal distortion present in S1, which are reduced drastically by high temperature annealed S2 sample. The fabricated solar cell with S1 and S2 absorbers showed significant improvement in efficiency from ~0.145% to ~1%. The presence of excess Sn in S1 allows enhanced recombination and the diode ideality factor shows larger value of 4.23 compared to 2.17 in case of S2. The experiments also validate the fact that S1 with Sn rich configuration shows lower acceptor carrier concentration as compared to S2 because of enhanced compensating defects in S1.

physics.app-ph↗