Electronic Structures And Optical Properties Of Doped Cubic BaTiO₃ Ceramics

Using the framework of the first-principles calculation method based on the density functional theory,the present research investigated the electronic structures and the optical properties of the doped cubic BaTi03 ceramics in which the Ti sites or Ba sites replaced partly and uniformly by other elements.The results showed that the pure cubic BaTi03 is direct bandgap semiconductor with a forbidden band width of 1.788 eV,and occurred with Ti atoms and O atom orbital hybrids between the bands.The dielectric constant is 0 when the photon energy is 0 eV,indicating that pure BaTiO3 system has weak response to photons and nonlinear changes in different energy ranges,and the optical absorption edge at 1.5 eV with the absorption spectrum peaks up to 140000,the electronic transition between reflection bands at 4.8 to 8.0 eV with the reflectance is around 0.6.Besides,the doping elements V,Fe and Co replaced the Ti sites in the BaTiO3 system,specifically,doping changed the space group structure of the system and it appeared with impurity levels at the same time,making the energy required for electron transition between bands reduced and V atom was more likely to occupy the Ti position of the BaTi03 system.Meanwhile,the incorporation of impurity atoms enhanced the dielectric properties of the BaTi03 system,improved the photoelectric response capability,the optical absorption edge has changed and the absorption coefficient and refection coefficient has increased.In addition the doping elements Mg,Ca and Sr replaced the Ba sites in the BaTi03 system,it has been found that doping also changed the space group structure of the system but it did not occurred with the impurity levels,the band gap of the doped system of Mg and Ca atoms increased with doping concentration increased.However,the band gap of the doped system of Sr atom decreased and Sr atom was more likely to occupy the Ba position of the BaTi03 system.In addition,the incorporation of impurity atoms enhanced the dielectric properties of the BaTiO3 system,improved the photoelectric response capability and increased the absorption coefficient while refection coefficient was deceased.