Understanding the Seebeck coefficient of LaNiO3 compound in the temperature range 300-620 K

Abstract: Transition metal oxides have been attracted much attention in thermoelectric community from the last few decades. In the present work, we have synthesized LaNiO${3}$ by a simple solution combustion process. To analyze the crystal structure and structural parameters we have used Rietveld refinement method wherein FullProf software is employed. The room temperature x-ray diffraction indicates the trigonal structure with space group $R \, \overline{3} \, c$ (No. 167). The refined values of lattice parameters are a = b = 5.4615 \AA\, $&$ c = 13.1777 \AA. Temperature dependent Seebeck coefficient (S) of this compound has been investigated by using experimental and computational tools. The measurement of S is conducted in the temperature range $300-620$ K. The measured values of S in the entire temperature range have negative sign that indicates \textit{n}-type character of the compound. The value of S is found to be $\sim$ $-$8 $\mu$V/K at 300 K and at 620 K this value is $\sim$ $-$12 $\mu$V/K. The electronic structure calculation is carried out using DFT+\textit{U} method due to having strong correlation in LaNiO${3}$. The calculation predicts the metallic ground state of the compound. Temperature dependent S is calculated using BoltzTraP package and compared with experiment. The best matching between experimental and calculated values of S is observed when self-interaction correction is employed as double counting correction in spin-polarized DFT + \textit{U} (= 1 eV) calculation. Based on the computational results maximum power factors are also calculated for \textit{p}-type and \textit{n}-type doping of this compound.