Theoretical study of physical properties of Ba3B(Nb,Ta)2O9 (B = Mg, Ca, Sr, Cd, Hg, Zn, Fe, Mn, Ni, Co) perovskites

The electronic structure, optical and thermoelectric properties of Ba3B(Nb,Ta)(2)O-9 are investigated by first principal calculation based on the density functional theory implemented in Wien2k simulation program. This study is carried out by applying GGA-PBE and GGA-EV potential. We have found that Ba3B(Nb,Ta)(2)O-9(B-Sr, Mg, Ca, Hg, Zn and Fe) materials are semiconductors and energy band gap varying in the range from 0.73 eV to 5.26 eV, whereas metallic character is observed in Ba3B(Nb, Ta)(2)O-9(B= Ni, Mn and Co) compounds. The structure stability of these materials was confirmed by formation energy. Moreover, the optical properties of the material in question are also examined and discussed. In addition, the temperature-dependent thermoelectric properties have been studied by calculating the electronic thermal conductivity (kappa), Seebeck coefficient (S), power factor (PF = sigma S-2/tau), and electrical conductivity (sigma/tau). High ZT values of 0.991, 0.998, 0.979, 0.993, 0.995, 0.996, 1.988 and 2.041 at room temperature for Ba3FeNb2O9, Ba3FeTa2O9, Ba3HgNb2O9, Ba3SrNb2O9, Ba3ZnNb2O9, Ba3Zn-Ta2O9, Ba3HgTa2O9, and Ba3SrTa2O9, respectively. Based on our calculations, predicting Ba-3(Sr, Hg)Ta2O9 as a good candidates for thermoelectric applications.