# High thermoelectric figure of merit and thermopower in layered perovskite oxides

## TL;DR

This study predicts high thermoelectric efficiency in layered perovskite La$_2$Ti$_2$O$_7$ through ab-initio calculations, showing a figure of merit exceeding 2.5 at high temperatures due to low thermal conductivity and favorable electronic properties.

## Contribution

The paper provides the first detailed ab-initio prediction of thermoelectric performance in La$_2$Ti$_2$O$_7$, highlighting its potential for high efficiency at elevated temperatures.

## Key findings

- ZT exceeds 2.5 at 1200 K
- Seebeck coefficient reaches nearly 1 mV/K at low doping
- Lattice thermal conductivity is around 1 W/(K·m) due to phonon confinement

## Abstract

We predict high thermoelectric efficiency in the layered perovskite La$_2$Ti$_2$O$_7$, based on calculations (mostly ab-initio) of the electronic structure, transport coefficients, and thermal conductivity in a wide temperature range. The figure of merit $ZT$ computed with a temperature-dependent relaxation time increases monotonically from just above 1 at room temperature to over 2.5 at 1200 K, at an optimal carrier density of around 10$^{20}$ cm$^{-3}$. The Seebeck thermopower coefficient is between 200 and 300 $\mu$V/K at optimal doping, but can reach nearly 1 mV/K at low doping. Much of the potential of this material is due to its lattice thermal conductivity of order 1 W/(K m); using a model based on ab initio anharmonic calculations, we interpret this low value as due to effective phonon confinement within the layered-structure blocks.