Electrical transport and thermoelectric properties of silver nanoparticles

TL;DR

This study investigates how reducing the size of silver nanoparticles affects their electrical resistivity, Debye temperature, and thermoelectric properties, revealing size-dependent modifications in electron-phonon interactions and thermoelectric performance.

Contribution

It provides detailed insights into size-dependent electrical and thermoelectric behaviors of silver nanoparticles, highlighting the impact of surface effects and electron-phonon coupling.

Findings

Debye temperature decreases with size reduction

Phonon drag features are suppressed and shifted in nanoparticles

Thermoelectric power factor is evaluated for different sizes

Abstract

Debye temperature decrease, residual resistivity increase and electron-phonon coupling constant increase as crystallite size decreases have been found from electrical resistivity in temperature range 5 K to 300 K of well-characterized Ag nanoparticles synthesized with oleylamine, trioctylphosphine and/ polyvinylpyrrolidone with Scherrer sizes ranging from 15.1 nm to 33.4 nm. Notably, about 36 % reduction in Debye temperature in 15.1 nm compared to bulk Ag is found. Remarkably, usual phonon drag peak found in Seebeck coefficient for bulk Ag turned into dips or phonon drag minima in these NPs that gradually gets suppressed and shifted towards lower temperature with decrease in crystallite size in oleylamine and trioctylphosphine-induced NPs. Contrastingly, it appears at higher temperature in trioctylphosphine-induced nanoparticles. A broad hump between 125 K to 215 K, a slope change near 270 K in resistivity and an additional dip-like feature near 172 K in Seebeck coefficient are seen in oleylamine-polyvinylpyrrolidone-induced nanoparticles with different shapes. They are attributed to spatial confinement of electrons and phonons, varying barrier heights, different charge-transfer mechanisms among metal nanoparticles and surfactant/s, enhanced disorders (grain boundaries, increase in fraction of surface atoms, surfactant matrix and other defects), leading to modifications in their overall electron and phonon interactions. Finally, their thermoelectric power factor has also been assessed.