The Study On The Pressure Control Mechanism Of The Thermoelectric Properties Of Ce₃Te₄System

Nowadays, energy plays an important role in both economic and socialdevelopment with rapid economic development. So far，energy is almost rely onnon-renewable resources. But with the global industrial growth and the populationbomb, these non-renewable mineral resources will be exhausted gradually, and theenergy crisis will erupt. Therefore, the energy crisis becomes a global issue of allmankind. The development of materials for renewable energy has become animportant topic between all materials scientists all over the world. Among them,thermoelectric material, which can convert the heat and the electricity from each other,has become an important object of the study by scholars. The conversion efficiency ischaracterized by Figure of merit (ZT). We can figure it out that for those goodthermoelectric materials should possess high Seebeck coefficient and high electricalconductivity with low thermal conductivity. However these three parameters influenceand control each other in one material. Therefore, a low conversion efficiency of athermoelectric material limits the application of the thermoelectric material.Firstly, our calculation based on first-principles density functional theory derivedthe band structure, the density of states and the charge density under zero pressure ofCe3Te4.We found that the Fermi level around conduction band performs a very highenergy-band overlapping, and that the density of states around the Fermi level showsa same form as the Dirac function from the density of states diagram. An analysis ofPDOS diagram indicates that the density of states with the form of the Dirac functionis mainly contributed by the electron of4f orbit from Ce atom. Using Mahan and Sofotheory and some ideal empirical parameters, we calculated the thermoelectric figureof merit is13.9429under the zero pressure at T=1200K. After calculating the crystalstructure under different pressures, the band structure, density of states and chargedensity are all different from the results under zero pressure, therefore, thethermoelectric properties of Ce3Te4changes with the pressure changes. Except the pressure equals1.5GPa, the peak of electron density of states with the form of Diracfunction around the Fermi level is higher than the height under the zero pressure, thehalf-height width were smaller than half-height width under the zero pressure,indicate that appropriate pressure applying can help to improve the thermoelectricproperties of crystals. Finally, the application of Mahan and Sofo theory and someideal empirical parameters helped us get the thermoelectric figure of merit withT=1200K under different pressures. We set the pressure ranges from1GPa to3GPaand found that the pressure under1.1GPa,1.2GPa,1.3GPa,2.5GPa, the ZT values arehigher than the ZT value under zero pressure in theory. And when the pressure is1.1GPa, the ZT value is13.9982, which is the highest value.