Theoretical investigation of electronic, optical and thermoelectric properties of tellurium doped barium titanate (BTO) through modified Becke – Johnson exchange potential

Abstract

The stability, electronic structure, optical and thermoelectric properties of Te -doped BaTiO3 are investigated by first-principal calculation based on the density functional theory and Boltzmann transport theory implemented in WIEN2K and BoltzTraP simulation program. This study is carried out by applying LDA + TB-mBJ potential. Formation energy of each doped structure is calculated to examine the stability and feasibility of the synthesis. Incorporating Te into BaTiO3 efficiently reduces the electronic band gap and the level of band gap reduction can be controlled by varying the amount of dopant (Eg = 2.752 eV for pure BTO and Eg = 0.500 eV for Te doped-BTO: 8.3 %). Hence, the absorption ability is improved in the visible light (380∼790 nm). Our findings suggest that all the doped structures are significantly absorbent and productive with an optical absorption that exceeds 105 cm−1 in the visible range (λ ∼ 500 nm). In addition, BaTiO3 revealed a smaller dielectric constant at zero frequency (ε10 = 3.98) compared to Te doped-BTO: 8.3 % (ε10 = 5.55), while the optical energy gap is reduced from 3.692 eV to 1.619 eV by growing Te concentration. Then, optical conductivity and Urbach's parameters are predicted. The transport properties are assessed as a function of temperature. It is found that the electrical conductivity is considerably enhanced with increasing Te concentration. Other thermoelectric properties such as Seebeck coefficient and figure of merit are also investigated. Our theoretical results can be useful for thermoelectric and visible-light photoelectrical device applications.