Effect of impurity and temperature changes on the thermoelectric properties of the (6, 3) two sided-closed single-walled boron nitride nanotubes ((6, 3) TSC-SWBNNTs)
In this study, the thermoelectric properties of the (6, 3) two sided-closed single-walled boron nitride nanotubes are investigated. To examine the effect of the impurity on the thermoelectric properties, carbon atom is replaced instead of boron and nitrogen atoms at the center, left and right the nanotube. The energy range is selected as -5.5 to 5.5 eV and temperatures is considered as 200, 300, 500, 700, 900, 1100 and 1300K. Investigations show that with increasing temperature and creating impurity, the bandgap of the nanotube significantly reduces. The greatest reduction in the bandgap and the least reduction in the height of the peaks is related to the temperature of 1300 K, in which the carbon atom is replaced instead of nitrogen atom in the center of the nanotube. By increasing temperature, the number of peaks decreases, the mobility of electrons and holes increases and their localization decreases. Also, results show that the largest Seebeck coefficient is related to the temperature of 1300 K and in the case of carbon impurity instead of boron atom at the left side of the nanotube. The magnitude of the maximum of Seebeck coefficient is about 500μV/K. Besides, the minimum amount of Seebeck coefficient is about -600 μV/K, which is related to carbon impurity instead of boron at the center of (6.3) TSC-SWBNNT. The largest thermal conductivity is equal to 5.1 nW/K which is related to the pure (6, 3) TSC-SWBNNT at the energy of – 4.3eV. The thermal conductivity values are in the nano (10-9) range, which is small amounts. Studies demonstration that the highest amount of ZT is equal to 1.65 which is related to the impurity of carbon atom instead of boron on the right side of the (6.3) TSC-SWBNNT at the temperature of 1300 K. This value occurs at the energy of -5.2 eV. As the values of ZT are larger than 1, especially at high temperatures, one can conclude that (6, 3) TSC-SWBNNTs is suitable selection as a thermoelectric material.