arXiv subjects

Vinayak B. Kamble

Publications and source records attributed to Vinayak B. Kamble.

6 recordsLinked to original sources

arXiv2026

Photo-thermoelectrics of a distributed Schottky junction system: Delineating the photo and thermal currents

Hybrid materials, consisting of diverse materials combined in various configurations, exhibit intriguing opto-electronic properties and are a focal point of research in functional materials. However, achieving precise predictability and tunability of their macroscopic properties in terms of the control parameters remains a challenge. One promising approach involves leveraging self-organization through eutectic growth and subsequent engineering via annealing to engineer niche properties. Here, the electronic properties of eutectic NiTiO$_3$-TiO$_2$ samples and their H$_2$-reduced counterpart Ni-TiO$_2$ are investigated, where the latter features high aspect ratio TiO$_2$ nanostructures decorated with nodular Ni globules. By exploiting this unique architecture and capitalizing on the nanostructuring processes alongside material properties, performance enhancement of photoactive devices is shown. Further, the competing mechanisms of photo-driven and photo-thermal-driven transport is delineated to characterize the overall photo-response of the system. The ability for self-powered functionality further showcases this approach as a promising strategy for developing efficient self-powered devices.

physics.app-ph↗

arXiv2026

Favorable half-Heusler structure of synthesized TiCoSb alloy: a theoretical and experimental study

The most favorable structure of the synthesized TiCoSb half-Heusler alloy is explored theoretically and experimentally, and the best structure for thermoelectric conversion is reported. Rietveld refinement of the X-ray diffraction data employing four probable structures of the HH alloy is performed to obtain the best fit and identify the crystallized structure. However, microstructural characterization is performed using the energy dispersive X-ray spectroscopy and transmission electron microscopy to reveal the stoichiometry and Bragg reflection planes of the synthesized polycrystalline lattice structure of TiCoSb HH alloy. Theoretical investigation is performed by implementing the first principle calculation using the Full Potential Linearized Augmented Plane Wave method in the Quantum Espresso software package. The most probable structure is explored by estimating the minimum energy at equilibrium volume and electronic structure of the TiCoSb half-Heusler alloy of the four probable structures considered. The theoretical and experimental data are corroborated, and the most probable structure is identified for the crystallized TiCoSb HH alloy. The thermoelectric properties of the most probable structure are estimated.

cond-mat.mtrl-sci↗

arXiv2025

Investigation of Softer Lattice Dynamics in Defect Engineered GeTe Crystals

The impact of Ge vacancies on the low-temperature lattice dynamics of single-crystalline GeTe was investigated through a comparative study of two off-stoichiometric samples: Ge$_{0.8}$Te (S$_1$) and Ge$_{0.88}$Te (S$_2$). X-ray diffraction confirms their highly oriented crystalline nature mainly along the $h0l$ plane, while temperature-dependent Raman spectroscopy reveals pronounced anharmonicity in S$_1$, indicated by stronger three-phonon scattering in the in-plane E-mode. A suppressed Raman feature at $~$ 239 $cm^{-1}$ in S$_2$ suggests fewer disordered GeTe$_{4-n}$Ge$_n$ tetrahedra, correlating with reduced Ge-Ge bonding signatures. Machine-Learned Molecular Dynamics (MLMD) simulations show dominant Te contributions below 100 $cm^{-1}$, while Ge dominates above, particularly influencing the 120 $cm^{-1}$ mode affected by defects at the Ge-site. Complementary calculation of phonon linewidth via MLMD and Temperature-Dependent Effective Potential (TDEP) methods affirm the predominance of three-phonon scattering below 300 K. Specific heat measurements, modeled using Debye-Einstein formalism, show lower Debye temperatures ($θ_D$) of 172.3 $\pm$ 1.5 K in Ge$_{0.8}$Te and 176.6 $\pm$ 1.7 K for Ge$_{0.88}$Te respectively, confirming defect-induced lattice softening. Electrical resistivity analysis further corroborates this, indicating reduced effective phonon frequencies in $S_1$. Thus, our results establish that higher Ge vacancies lead to softer, and hence more anharmonic lattice dynamics in GeTe, with its relevance in designing superior thermoelectric and phase-change memory applications.

cond-mat.mtrl-sci↗

arXiv2024

Predicting the Realizable Maximum Power Factor using the Jonker and Ioffe formulation: Al-doped ZnO Triangular Microcrystals with Graphite Inclusion Case Study

Among the popular TE materials, selenides and tellurides are the benchmarks of high-efficiency systems. However, for the high-temperature application (>700 K), it is required to rely on the silicides and the oxides due to their exceptional thermal stability. ZnO is among the first few oxides in the field of thermoelectricity. Al-doped ZnO is a proven material for its high-temperature thermoelectric applications. However, the high grain boundary resistance limits further improvement of the efficiency of this oxide. Band-engineering, band-modification is a successful approach in lowering the grain boundary resistance. The addition of graphite and graphite-based materials at the grain boundaries is shown to serve this purpose. In this work, graphite powder is added in varying proportions to Al-doped ZnO triangular microcrystals. Thus, prepared materials are characterized to confirm the formation and investigate the nature of interface, morphology, etc. TE parameters such as electrical conductivity, Seebeck coefficient, and thermal conductivity of those materials also have been measured. The theoretical calculation of TE efficiency zT often differs from the actual experimental results due to the wide range of preparation methods, leading to changes in porosity, the nature and density defects, and several other factors. In this paper, an effort has been made to estimate the maximum achievable power factor (PFmax) from the measured TE parameters of this set of samples by the Jonker and Ioffe analysis. Based on the predicted PFmax, an appropriate material composition has been identified to achieve that same. Subsequently, including the measured parameters the TE efficiency (zT) is calculated. Further, a sudden dip observed in the thermal conductivity at the high-temperature range (625 K - 1000 K) of the prepared undoped ZnO graphite composite is investigated in this paper.

cond-mat.mtrl-sci↗

arXiv2020

Metal-polymer hybrid chemiresistive sensor for low concentration fast hydrogen detection

Low concentration hydrogen gas detection is of paramount importance both in space applications as well as medical applications. It is also critically important for safe handling of hydrogen below the explosive limit. Here, we report a novel hybrid Pd metal-polymer chemiresistive sensor that can sense 0.5% hydrogen ($H_2$) gas in ambient conditions of temperature and pressure with the highest reported sensitivity($\sim$30%) obtained earlier by a physical deposition technique, making it an extremely good sensor for real life low concentration hydrogen gas detection. The sensor is easy to fabricate and is also extremely cost-effective for commercial applications. The obtained hybrid chemiresistive sensor comprises palladium (Pd) nanocrystals bound by oxygen and nitrogen atoms of a stabilizer Polyvinylepyrollidone (PVP), grown on top of a selfassembled monolayer. The exceptional rise time-constant is proposed to arise from hydrogen loading at the (111) surface of the palladium nanocrystal which is a very fast process and subsequent fast diffusion of the H atoms from the surface into the bulk. An effort to increase the number of available sites by UV-ozone cleaning, resulted in a degradation of the sensing device due to the poisoning of the available sites by oxygen.

physics.app-ph↗

arXiv2020

Thickness induced metal to insulator charge transport and unusual hydrogen response in granular palladium nanofilms

This work reports a systematic study of the evolution of charge transport mechanism in granular ultra-thin films of palladium of thickness varying between 6nm and 2nm. While the films with thickness > 4nm exhibit metallic behaviour, that at 3nm thickness undergoes a metal-insulator transition at 19.5K. In contrast, the 2nm thick film remained insulating at all temperatures. with transport following Mott's variable range hopping. At room temperature, while the thicker film exhibit resistance decrease on H$_2$ exposure. the insulating film showed an anomalous initial resistance increase before switching to a subsequent decrease. The nanostructure dependent transport and the ensuing H$_2$ response is modeled on a percolation model, which also explores the relevance of film thickness as a macroscopic control parameter to engineer the desired system response in granular metal films.

cond-mat.mtrl-sci↗