Perpustakaan Digital ITB

Thermoelectric materials can convert heat into electricity, or conversely, produce heating or cooling from electrical current. However, the potential applications of thermoelectric materials to date are limited due to the low efficiency (expressed by the dimensionless quantitiy known as figure of merit, ZT ) of existing thermoelectric materials. One of the proposed methods for obtaining high efficiency thermoelectric material is by using a pudding mold band structure, that is, a material where the energy dispersion of the bands depend on the fourth or greater power of the wave number. In this final project, we consider the effects of a pudding mold type band structure to the thermoelectric properties of the material. Furthermore, it has been observed that a high figure of merit can be obtained by tuning the band gap of the material to an optimum value. Therefore, we also consider the effect of the band gap to the thermoelectric properties of the material. We also calculate the thermoelectric properties of 2D and 1D materials. To calculate the thermoelectric properties of the material, we use the Boltzmann transport theory with the relaxation time approximation. The required numerical calculations are done using the SciPy library of the Python programming language. We also calculate the thermoelectric properties of real life pudding mold material such as FeAs2 and PtS2 using Quantum ESPRESSO and BoltzTraP software. The results of the calculations show that the pudding mold band structure produces a higher electrical and thermal conductivity than a parabolic band, but no significant difference is found between the Seebeck coefficient for the pudding mold band structure and the Seebeck coefficient of the parabolic band. Meanwhile, variation of the band gap shows that increasing the band gap will increase the figure of merit up until around 5kBT , where further increase of the band gap will not increase the figure of merit. Another interesting result is the increase in figure of merit obtained when the shape of conduction band is different from the shape of the valence band. We found that the results for two dimensional materials are similar to the result for 3D material, but surprisingly we found that the figure of merit for 1D material with parabolic bands is higher than for 1D material with pudding mold band due to its higher density of states. From the calculations using real materials, we found that our pudding mold materials exhibit a higher figure of merit compared to silicon (parabolic band). We can conclude that to maximize the figure of merit we need a material with a pudding mold type band structure and a high band gap, or otherwise, for a low band gap material, a higher figure of merit can be achieved by using an asymmetrical conduction band and valence band structure.