Study On The Ferroelectric Properties Of （BaSr）（ZrTi）O₃

Barium titanate（BaTiO₃）,as a typical perovskite ferroelectric material,has excellent physical property,such as high dielectric constant,positive temperature coefficient,ferroelectricity,thermoelectricity and piezoelectricity.Especially,Ba Ti O₃doped has high performance in ferroelectricity and dielectric property.It is widely used in multilayer ceramic capacitors,piezoelectric ceramic converters,non-volatile memory,infrared sensors and temperature controllers.In order to study further the ferroelectricity of Ba Ti O₃,the electronic structure,ferroelectricity and optical properties of(Ba_0.875Sr_0.125)(Zr_xTi_1-x)O₃（BSZT）at the different concentrations of Zr doped are investigated using a first-principles calculation method based on density function theory.At the same time,the interfacial interactions between the Ba Ti O₃（00 1）surface and butanol isomer molecules are also calculated.Firstly,the theoretical model of(Ba_0.875Sr_0.125)(Zr_xTi_1-x)O₃（x=0.125）was constructed to study Zr doping behavior at the low concentration.The calculation on the relaxation structure and the electron charge density indicates that the doping of Sr and Zr leads to the distortion of Ti O₆ octahedron.The double well curves of pure Ba Ti O₃ and BSZT fits well with the Landau-Ginzburg model.The spontaneous polarization of BSZT is lower than that of pure Ba Ti O₃,indicating that its ferroelectric properties are weakened.The density of states analysis shows that there is a strong hybridization between the 3d orbital of Ti atom and the 2p orbital of O,and there is a strong hybridization between the 4d orbital of Zr and the 2p orbital of O.Compared with pure Ba Ti O₃,the optical properties of BSZT are blue-shifted,and the light absorption and reflectivity are enhanced in the deep ultraviolet region.In the middle ultraviolet region,the role of Sr atoms in co-doping is obvious;in the deep ultraviolet region,the effect of Zr atoms is more significant.Secondly,the theoretical model of(Ba_0.875Sr_0.125)(Zr_xTi_1-x)O₃（x=0.25,0.5,0.75）was constructed by increasing the doping concentration of Zr atoms.According to the results calculated,the spontaneous polarization of different doping concentration models decreases with the increase of doping concentration,indicating that the ferroelectric properties of BSZT decrease with the increase of Zr doping concentration.When x=0.25,the potential well depth reaches a maximum of 1.83me V.All the four doping models have direct band gap,and the maximum band gap is 3.75 e V when x=0.25.As the doping concentration increases,the contribution of the 3d orbital of the Ti atom in the conduction band gradually decreases,and the contribution of the 4d orbital of the Zr atom gradually increases.The optical properties of BSZT materials have different performances with the change of doping concentration.The static dielectric constant and static refractive index decrease with the increase of doping concentration.The optical absorption increases with the increase of Zr doping concentration in the ultraviolet range of 6.29～7.62 e V and30.99～36.13 e V,and decreases with the increase of Zr doping concentration in the ultraviolet range of 17.55～19.12 e V and 38.61～42.66 e V.The reflectivity and refractive index also have similar changes.Finally,the adsorption behavior of butanol isomers（n-butanol,tert-butanol,sec-butanol,iso-butanol）on Ba Ti O₃（0 0 1）surface was studied.The adsorption configurations of butanol isomers and Ba Ti O₃（0 0 1）surface were constructed.to compare the adsorption energy,and the most stable adsorption structure of butanol isomers was picked out.The adsorption process was judged to be chemical adsorption according to the calculation of adsorption energy.During the adsorption process,the O-H bond of the butanol molecule dissociates,and the H atom combines with the O2 atom on the Ba Ti O₃（0 0 1）surface to form a covalent bond.There is charge transfer between butanol molecule and Ba Ti O₃ surface.The butanol molecule acts as an electron acceptor to accept electrons from the Ba Ti O₃（0 0 1）surface.The charge difference density diagram visually shows the charge transfer path.