arXiv subjects

Vinayak B Kamble

Publications and source records attributed to Vinayak B Kamble.

5 recordsLinked to original sources

arXiv2025

Hierarchically Engineered Titanium Suboxide Films for High-Efficiency Solar Thermal Conversion

We report the development of broadband solar absorber coatings based on titanium suboxide composite thin films on aluminium substrates. The films are fabricated via scalable DC magnetron sputtering using a Ti target, followed by post-annealing in a fixed $O_2$ partial pressure of 0.45 mbar. By tuning deposition time and annealing temperature, a composite phase of $Ti_2O_3$ and $TiO_2$ was achieved. The Raman mapping of the films substantiates the distribution and coexistence of the two phases. The optimized sample, deposited for 10 min and annealed at 500 $^oC$, exhibited a superior solar absorptance ($α_s$ = 0.913) and optimally low thermal emittance ($ε_t$ = 0.11). Nevertheless, the 15- and 20-min deposited films also showed a promising absorptance (>0.85) and emittance values (<0.13). Morphological studies revealed island-type nanostructures, leading to enhanced photothermal performance via electric field confinement, which is validated by optical simulations. This work provides a promising route toward efficient, scalable, and cost-effective spectrally selective solar absorbers for solar thermal applications.

cond-mat.mtrl-sci↗

arXiv2024

Coexistence of Multiple Magnetic Interactions in Oxygen Deficient V2O5 Nanoparticles

This paper reports on the spin glass-like coexistence of competing magnetic orders in oxygen-deficient V2O5 nanoparticles having a broad size distribution. X-ray photoelectron spectroscopy yields the surface chemical stoichiometry of nearly V2O4.65 due to significant defect density. Temperature-dependent electrical conductivity and thermopower measurements demonstrate a polaronic conduction mechanism with a hopping energy of about 0.112 eV. The V2O5-δ sample exhibits strong field as well as temperature-dependent magnetic behaviour when measured with a SQUID magnetometer, showing positive magnetic susceptibility across the temperature range of 2-350 K. Field-cooled and zero-field-cooled data indicate hysteresis, suggesting glassy behaviour. The formation of small polarons due to oxygen vacancy defects, compensated by V4+ charge defects, results in Magneto-Electronic Phase Separation (MEPS) and various magnetic exchanges, as predicted by first-principle calculations. This is evidenced by the strong hybridisation of V orbitals in the vicinity of vacant oxygen site. An increase in V4+ defects shows an antiferromagnetic (AFM) component. The magnetic diversity in undoped V2O4.9 originates from defect density and their random distribution, leading to MEPS. This involves localised spins in polarons and ferromagnetic (FM) clusters on a paramagnetic (PM) background, while V4+ dimers induce AFM interactions. Electron paramagnetic resonance spectra measured at different temperatures indicate a dominant paramagnetic signal at a g-value of 1.97 due to oxygen defects, with a broad FM resonance-like hump. Both signals diminish with increasing temperature. Neutron diffraction data rules out long-range magnetic ordering, reflecting the composition as V2O4.886. Despite the FM hysteresis, no long-range order is observed in ND data, consistent with the polaron cluster-like FM with MEPS nature.

cond-mat.mtrl-sci↗

arXiv2022

CVD Growth of Tin Selenide Thin Films for Optoelectronic Applications

Tin Selenide (SnSe) thin films were grown onto glass and alumina substrates by Chemical Vapor Deposition (CVD) method. The structural, micro-structural and morphological characterizations of the as grown thin films were investigated using XRD, SEM and Raman spectroscopy which reveals that the films on glass are phase pure oriented SnSe while those on Alumina are polycrystalline SnSe with SnSe2 impurity phase. The optical properties of the films grown onto glass substrate were studied by UV-vis spectroscopy. The optical band gap calculated is 1 to 1.3 eV for indirect and direct transition in film deposited on glass substrates. The Arrhenius plots of the two films show very different thermal activations i.e. 0.088 eV for tin vacancy acceptor level close to valance band maxima in pure SnSe and 0.44 eV for mid gap selenium vacancies of SnSe2. Photoresponse was observed by illuminating the sample (Glass and alumina Substrate) using white and UV light (400 nm) for a fixed time pulses. The deposited onto Alumina substrate were found to show better photoresponse due to SnSe/SnSe2 p-n heterojunctions.

cond-mat.mtrl-sci↗

arXiv2021

Protonic Conduction Induced Selective Room Temperature Hydrogen Response in ZnO/NiO Heterojunction Surfaces

In this paper we show that the ionic conduction through surface chemisorbed ambient moisture leads to the remarkably high room temperature selective response towards hydrogen gas. The surface adsorbed moisture acts as surface states and shows ionic conduction, as a result of smaller size of ZnO nanoparticles of 20 +/- 5 nm. This response is enhanced remarkably i.e. from 10% to 190% for 1200 ppm H2 gas when p-type NiO quasi-nanowires (width ~50 nm) are mixed with these n-type ZnO nanoparticles to form a homogenous NiO/ZnO nano-bulk p-n heterostructure. The maximum response is obtained for about 50-50 % composition of NiO/ZnO although it is of still n-type character. The dominant carrier type reversal from n to p type takes place at rather high NiO content of about 60-80% in ZnO, depicting dominating contribution of ZnO into the response. The parallel surface ionic current through chemisorbed moisture (surface states) has been identified as a primary factor for high sensitivity at room temperature. Thus, the presence of heterojunction barrier at the NiO-ZnO interface assisted with the surface ionic conductivity due to adsorbed moisture results in large, selective response to hydrogen at room temperature.

cond-mat.mtrl-sci↗

arXiv2019

Simple, Reversible Gradient Seebeck Coefficient Measurement System for 300-600K

An in-house Seebeck coefficient measurement system has been developed which can measure the thermoemf (Seebeck coefficient) of the sample, under large temperature difference, in the temperature range 300-600 K. Unlike majority of reported instrumental designs, the system does not have a hot walled chamber and hence is much closer to real time thermoelectric applications conditions. The system consists of two brass blocks supported heaters. These heaters are placed on either side of the sample through silver caps, thus allows individual temperature control. A reversible temperature gradient is applied across the sample and the measurement is carried out in quasi-static direct current mode. Hence, a more accurate Seebeck coefficient measurement is obtained.

physics.ins-det↗