Exploring the effect of strong electronic correlations in Seebeck Coefficient of the NdCoO3 compound : Using experimental and DFT+U approach

The presence of complexity in the electronic structure of strongly correlated electron system NdCoO$_3$ (NCO) have sparked interest in the investigation of its physical properties. Here, we study the the Seebeck coefficient ($\alpha$) of NCO by using the combined experimental and DFT+$U$ based methods. The experimentally measured $\alpha$ is found to be $\sim$ 444 $\mu V/K$ at 300 K, which decreases to 109.8 $\mu V/K$ at 600 K. In order to understand the measured $\alpha$, we have calculated the PDOS and band structure of the NCO. Furthermore, the calculated occupancy of 6.4 for Co $3d$ orbitals and presence of large unoccupied O $2p$ states indicate the covalent nature of the bonding. Apart from this, the maximum effective mass is found to be 36.75 (28.13) for the spin-up (dn) channel in conduction band indicates the n-type behaviour of the compound in contrast to our experimentally observed p-type behaviour. While, the calculated $\alpha$ at the temperature-dependent chemical potential ($\mu$) at 300 K shows the p-type behaviour of the compound. Fairly good agreement is seen between the calculated and measured values of $\alpha$ at U$_f$$_f$ = 5.5 eV and U$_d$$_d$ = 2.7 eV. The maximum power factor (PF) is found to be 47.6 (114.4) $\times$ $10^1$$^4$ $\mu$$W$$K^-$$^2$$cm^-$$^1$$s^-$$^1$ at 1100 K, which corresponds to p (n)-type doping of $\sim$ 1.4 (0.7) $\times$ 10$^2$$^1$ cm$^-$$^3$. This study suggests the importance of strong on-site electron correlation in understanding the thermoelectric property of the compound.