| 초록 |
Nowadays, thermoelectric applications have been developed due to its potential ability to convert waste heat into electricity. Thermoelectric efficiency is evaluated by the dimensionless figure of merit ZT=S2σT/κ, where S is Seebeck coefficient, σ is the electrical conductivity and κ is the thermal conductivity. To obtain the maximum figure of merit (ZT), theremoelectric materials have to simultaneously exhibit high Seebeck coefficient S, high electrical conductivity σ and low thermal conductivity κ. However, each parameter was complementary connected with each other based on scattering mechanisms of charge carriers and lattice vibrations. Among metal oxides, perovskite (ABO3) thermoelectric materials have been intensively interested because electrical and Seebeck characteristics can be easily adjusted via crystal structure engineering. Especially, perovskite lanthanum manganese oxide (LaMnO3) have been found to exhibit wide variation of electrical conductivity, which can be easily distorted by different ion doping with thermal treatment at La site. In this study, we have investigated p-type thermoelectric La1-xCaxMnO3 (LCMO) materials via density functional theory (DFT) simulation with thermodynamic variations to optimize power factors (S2σ), which directly affect thermoelectric characteristics in the perovskite materials. The thermodynamic variations were adjusted by both compositional (La1-xCaxMnO3, x = 0, 0.13, 0.25, 0.5, 0.63, 0.75, 0.88) and thermal treatment optimizations. Further, electronic transport properties of La1-xCaxMnO3 were calculated by using Boltzmann theory transport equation approximation. The results illustrate that the La1-xCaxMnO3 materials were found to exhibit a calculated optimum power factor in 570 μW/mK-2 at x = 0.5 with post treatment temperature of 1300 K. |
