Investigation of the Thermoelectric Properties of ZnV$_{2}$O$_{4}$ Compound in High Temperature Region

Abstract

In the present work, we report the experimental thermopower ($\alpha$) data for ZnV$_{2}$O$_{4}$ compound in the high temperature range 300-600 K. The value of $\alpha$ is found to be $\sim$184 and $\sim$126 $\mu$V/K at $\sim$300 and $\sim$600 K, respectively. The temperature dependent behavior of $\alpha$ is almost linear in the measured temperature range. To understand the large and positive $\alpha$ value observed in this compound, we have also investigated the electronic and thermoelectric properties by combining the \textit{ab-initio} electronic structures calculations with Boltzmann transport theory. Within the local spin density approximation plus Hubbard U, the anti-ferromagnetic ground state calculation gives an energy gap $\sim$0.33 eV for U=3.7 eV, which is in accordance with the experimental results. The effective mass for holes in the valance band is found nearly four times that of electrons in conduction band. The large effective mass of holes are mainly responsible for the observed positive and large $\alpha$ value in this compound. There is reasonably good matching between calculated and experimental $\alpha$ data in the temperature range 300-410 K. The power factor calculation shows that thermoelectric properties in high temperature region can be enhanced by tuning the sample synthesis conditions and suitable doping. The estimated value of \textit{figure-of-merit}, ZT, at different absolute temperature suggest that ZnV$_{2}$O$_{4}$ compound can be a good thermoelectric material in high temperature range.