Exploring the possibility of enhancing the high figure-of-merit ( >>> 2) of Na${0.74}$CoO${2}$ by using combined experimental and theoretical studies (original) (raw)

Search of new thermoelectric (TE) materials with high figure-of-merit (ZT) is always inspired the researcher in TE field. Here, we present a combined experimental and theoretical study of TE properties of Na$_{0.74}$CoO$_{2}$ compound in high temperature region. The experimental Seebeck coefficient is found to vary from 64 to 118 mu\mumuV/K in the temperature range 300 - 620 K. The positive values of S are indicating the dominating p-type behaviour of the compound. The observed values of thermal conductivity ($\kappa$) are found to be 2.2 to 2.6 W/m-K. To understand the experimental transport properties, we have carried out the calculations using DFT and DFT+U. The best matching between experimental and calculated values are observed when the calculation is done by chosen U = 4 eV in DFT+U. Calculations predict the half-metallic ferromagnetic ground state of the compound. By taking calculated S and electrical conductivity along with experimental kappa\kappakappa, we have optimized the ZT valu...