arXiv subjects

Navdeep Goyal

Publications and source records attributed to Navdeep Goyal.

5 recordsLinked to original sources

arXiv2024

Understanding the transport behaviour of PbSe: A combined experimental and computational study

Lead chalcogenides are the promising thermoelectric (TE) materials having narrow band gap. The present work investigates the TE behaviour of PbSe in the temperature range 300-500 K. The transport properties of the sample have been studied using the Abinit and BoltzTrap code. The experimentally observed value of \textit{S} at 300 and 500 K is found to be $\sim$ 198 and 266 $\mu$V K$^{-1}$, respectively. The rate of increase in \emph{S} from 300 to 460 (460 to 500) K is found to be $\sim$ 0.4 (0.09). The temperature dependent electrical conductivity \textit{($\sigma$)} shows the increasing trend, with values of $\sim $ 0.35 $\times $ 10$^{3}$ and $\sim$ 0.58 $\times$ 10$^{3}$ $\Omega$$^{-1}$ m$^{-1}$ at 300 and 500 K, respectively. Further, the value of thermal conductivity \textit{($\kappa$)} at 300 (500) K is found to be 0.74 (1.07) W m$^{-1}$ K$^{-1}$. The value of \textit{$\kappa$} is found to be increasing upto 460 K and then starts decreasing. The dispersion plot indicates that PbSe is a direct band gap semiconductor with band gap value of 0.16 (0.27) eV considering spin-orbit coupling (without SOC). The partial density of states (PDOS) plot shows that Pb 6p and Se 4p states have a major contribution in the transport properties. The observed and calculated values of \textit{S} gives a good match for SOC case. The calculated \textit{$\sigma$} and electronic part of thermal conductivity (\textit{$\kappa{_e}$}) gives good match with the experimental data. The maximum power factor (PF) value of $\sim$ 4.3 $\times$ 10$^{-5}$ W/mK$^{2}$ is observed at 500 K. This work helps in understanding the TE behaviour of PbSe through a novel and insightful alliance of experimental measurements and DFT approach.

cond-mat.mtrl-sci↗

arXiv2019

Investigating Phase Transition and Morphology of Bi-Te Thermoelectric System

The optimization of secondary phase in thermoelectric(TE) materials can {helps in improvisation of material's efficiency}. Being a potential {contender} for lower temperature TE application, bismuth telluride(Bi$_2$Te$_3$) nanoparticles were synthesized via different routes and profiles to optimize their pure single phase. Systematic characterizations were performed with the help of X-ray diffraction (XRD), Rietveld refinement and field effect-scanning electron microscopy(FE-SEM) for structural and morphological behavior, while TE properties such as Seebeck coefficient, electrical conductivity and power-factor were measured for the purest sample chosen. Rietveld refinement in the XRD pattern of the samples revealed that only a small amount ($\sim$ 1.6\%) of Bi$_2$Te$_3$ was formed in co-precipitation method, while the hydrothermal technique increases this phase with increment in synthesis duration. This work focused on the phase evolution of Bi$_2$Te$_3$ with increasing synthesis duration time at constant temperature and vice-versa. XRD and Rietveld refinement revealed that the hydrothermal technique (150 $^\circ$C for 48 hours) can synthesize purest samples (84\% Bi$_2$Te$_3$ phase in this case). {FE-SEM and Energy Dispersive X-ray analysis unveiled that the impure phases in the system {were} quantitatively reduced, and it supported by decline in atomic percentage of oxygen from 37\% to 11\%, in addition to this, it was also found that particle size was also decreased with increase in temperature.} The observed electrical conductivity of the chosen sample is $\sim$20 times greater, while Seebeck coefficient is $\sim$3 times lower than that of pure Bi$_2$Te$_3$ phase. The detailed analysis has generalized the growth mechanism in Bi$_2$Te$_3$ phase evolution by the diffusion of Bi into Te nanorods to fabricate hexagonal Bi$_2$Te$_3$.

cond-mat.mtrl-sci↗

arXiv2018

Phase-evolution in Co-Sb System: CoSb3 Hydrothermal Synthesis

Nanostructure CoSb3 samples were synthesized via hydrothermal technique along with different routes to study the phaseevolution in Co-Sb system. X-ray diffraction (XRD) explored to study the phase evolution in Co-Sb system via. Special emphasis on rietveld refinement and scanning electron microscope (SEM) were evaluated to study morphology of the samples. The samples prepared using ramp-route showed presence of different phases that eventually helps in formation of pure phase CoSb3 skuterrudite. Using different solvents to eliminate NaCl impurity also shows that DI-water eliminates NaCl impurity better because of its high solubility.

cond-mat.mtrl-sci↗

arXiv2006

Effect of silver doping on the electrical properties of a-Sb$_2$Se$_3$

This paper reports the effect of Ag-doping on electrical properties of a-Sb2Se3 in the temperature range 240-340 K and frequency range 5 Hz to 100 kHz. The variation of transport properties with thermal doping has been studied. Ag-doping produced two homogeneous phases in the sample and which are found to be voltage dependent in the temperature range studied and frequency dependent in lower frequency region (0.1 - 10 kHz). Activation energy Eg and C' [=$\sigma_0$ exp ($\gamma$/k), where $\gamma$, is the temperature coefficient of the band gap] calculated from dc conductivity has been found to vary from 0.42 eV to 0.26 eV and 41.08x10$^-6$ to 2.902x10-6 $\ohm^{-1}$cm$^{-1}$ respectively. Ag-doping can be used to make the sample more useful in device applications.

cond-mat.mtrl-sci↗

arXiv1997

Opto-electronic application of AgInSe_2

The paper reports a possible application of AgInSe_2 for opto-electronic switching. Material has been studied over a wide range of frequencies (5Hz to 1MHz), through measurements of conductance and capacitance, at different temperatures and illumination levels. The results indicate that there is an increase in capacitance (C) as well as conductance (G), when sample is exposed to light radiations at a given temperature. The switching/recovery time has been analyzed in terms of time constant (τ= C/G) and found to be of the order of micro seconds for this material. It has been further observed that τdecreases with increasing illumination levels and temperature. It is understandable, because higher the rate of recombination of optically/thermally generated carriers, lesser should be the value of τ.

cond-mat.mtrl-sci↗