Understanding the Seebeck coefficient of LaNiO₃compound in the temperature range 300-620 K

Transition metal oxides have been attracted much attention in thermoelectric community from the last few decades. In the present work, we have synthesized LaNiO₃by a simple solution combustion process. To analyse 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 rhombohedral structure with space groupR3¯c(No. 167). The refined values of lattice parameters area=b=c= 5.4071 Å. Temperature dependent Seebeck coefficient (S) of this compound has been investigated by using experimental and computational tools. The measurement ofSis conducted in the temperature range 300-620 K. The measured values ofSin the entire temperature range have negative sign that indicates n-type character of the compound. The value ofSis found to be ∼-8μV/K at 300 K and at 620 K this value is ∼-12μV/K. The electronic structure calculation is carried out using DFT +Umethod due to having strong correlation in LaNiO₃. The calculation predicts the metallic ground state of the compound. Temperature dependentSis calculated using BoltzTraP package and compared with experiment. The best matching between experimental and calculated values ofSis observed when self-interaction correction is employed as double counting correction in spin-polarized DFT +U(=1 eV) calculation. Based on the computational results maximum power factors are also calculated for p-type and n-type doping of this compound.