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We report the thermoelectric (TE) properties ofNa$_{0.74}$Co$_{0.95}$Nb$_{0.05}$O$_{2}$ in the temperature range $300-1200$ K,as a potential candidate for p-type thermoelectric material. The experimentalvalues of Seebeck coefficient (S) are $ \sim $ $82-121$ $ \mu $V/K measured inthe temperature range $300-620$ K. The positive values of S in the entiretemperature range indicates p-type behaviour of the compound. At 300 K theexperimental value of thermal conductivity ($ \kappa $) is $ \sim $ 1.88 W/m-Kthat increases up to $ \sim $ 420 K, then decreases till 620 K withcorresponding value $ \sim $ 1.86 W/m-K. To understand the experimentallyobserved transport properties, we have calculated S and $\rho$ of thiscompound. Then, based on theoretical understanding, we have estimated\textit{figure-of-merit} (ZT) up to 1200 K by using calculated S and $\rho$values with extrapolated experimental $\kappa$. The value of ZT is found to be$\sim$ 0.03 at 300 K, whereas, the highest value is observed as $\sim$ 1.7 at1200 K. Finally, we have calculated the efficiency ($\eta$) by keeping the coldend temperature (T$_{c}$) fixed at 500 K and varying hot end temperature(T$_{h}$) from 500 to 1200 K, respectively. The maximum value of $\eta$ isfound to be $\sim$ 8 %, when T$_{c}$ and T$_{h}$ are fixed at 500 and 1200 K,respectively. This result suggests thatNa$_{0.74}$Co$_{0.95}$Nb$_{0.05}$O$_{2}$ compound can be used as a p-leg formaking high temperature TE generator (TEG).

Achieving high figure-of-merit in Nb-doped Na$_{0.74}$CoO$_{2}$ compound at high temperature region