Investigation of electronic, optical and thermoelectric properties of perovskite BaTMO3 (TM=Zr, Hf): First principles calculations

Abstract The structural, electronic, optical, and thermoelectric characteristics of crystalline oxides-perovskites BaTMO3 (TM=Zr or Hf) were investigated using the all-electron full-potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). The generalized gradient approximation as parameterized in Perdew, Burke, and Ernzerhof (PBE-GGA) was employed to calculate exchange-correlation potential. Also, the modified Becke Johnson exchange potential approximation as parameterized by Tarn and Blaha (TB-mBJ) was used to improve the bandgap estimation. According to our calculations, both perovskites BaZrO3 and BaHfO3 show insulator behavior and have widely indirect band-gap energy (R-Γ) 4.42 (3.39) eV for BaZrO3 and 5.25 (3.69) eV for BaHfO3 from both approaches, TB-mBJ (PBE-GGA), respectively. The optical properties such as dielectric tensor, the refractive index, the absorption coefficient, and the electron loss function have been calculated and analyzed. The optical transitions mainly take place if an electron radiate from the initial state O-2p to the final state Hf-5d or to the Zr-4d in BaHfO3 or BaZrO3 case, respectively. Furthermore, the transport characteristics calculations based on semi-classical Boltzmann theory have been discussed. The thermopower at RT of both compounds BaHfO3 and BaZrO3 are 260.47 and 208.33 μV/K, respectively. This result is good enough to consider these materials as promise thermoelectric candidates. Our results were compared with the previous ab intio calculations and experiments and showed a reasonable agreement.