Effect of nanostructure on thermoelectric properties of La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ in 300-600 K range

TL;DR

This study investigates how nanostructuring La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ affects its thermoelectric properties between 300-600 K, showing reduced thermal conductivity and increased ZT with smaller crystallite sizes, indicating potential for high-temperature thermoelectric applications.

Contribution

It demonstrates the impact of controlled nanostructuring on thermoelectric performance of LSMO, highlighting size-dependent improvements in ZT at elevated temperatures.

Findings

Thermal conductivity decreases with smaller crystallite size.

ZT increases at high temperatures, reaching 0.045 at 650 K.

Nanostructuring enhances thermoelectric efficiency of LSMO.

Abstract

In oxide materials, nanostructuring effect has been found very promising approach for the enhancement of \textit{figure-of-merit}, \textit{ZT}. In the present work, we have synthesized La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ (LSMO) compound using sol-gel method and samples of crystallite size of 34, 41, and 49 nm were obtained by giving different heat treatment. Seebeck coefficient ($\alpha$), electrical resistivity ($\rho$), and thermal conductivity ($\kappa$) measurements were carried out in 300-600 K temperature range. The systematic change in the values of $\alpha$ from $\sim$ -19 $\mu$V/K to $\sim$ -24 $\mu$V/K and drastic reduction in the values of $\kappa$ from $\sim$0.88 W/mK to $\sim$0.23 W/mK are observed as crystallite size is reduced from 49 nm to 34 nm at $\sim$600 K. Also, fall in the values of $\rho$ in the paramagnetic (PM) insulator phase (400-600 K) are effectively responsible for the increasing trend in the values of \textit{ZT} at high temperature. For the crystallite size of 41 nm, value of \textit{ZT} at 600 K was found to be $\sim$0.017, which can be further increased up to $\sim$0.045 around 650 K temperature. The predicted value of \textit{ZT} suggests that LSMO can be suitable oxide material for thermoelectric applications at high temperature.