First Principles Study On Properties Of Element Doped Barium Titanate(BaTiO₃)ceramics

As one of the important raw materials for producing electronic ceramic components,BaTiO₃ has high dielectric constant,low dielectric loss and excellent ferroelectric and piezoelectric properties.Therefore,BaTiO₃ ceramics has been the research hotspot of many scientists.At present,the research on doping modification and preparation technology of BaTiO₃ ceramics has achieved good results and is widely used in many high-tech fields.As one of the more mature theoretical research methods,the first principles method studies the material structure and properties from the micro scale,and has been widely used in the study of various material properties.In this manuscript,the first principle calculation method based on density functional theory is used to study the effects of 19 element X(X is Sc,V,Cr?Mn,Fe,Co,Ni,Cu,Zn,Y,Zr,Nb,Mo,Tc,Ru,Rh,Pd,Ag,Cd)doping on the crystal structure,enthalpy of formation,binding energy,electronic structure(band structure and density of states),magnetic properties,static dielectric constant and optical properties of BaTiO₃ ceramics.It provides a reference for the doping optimization design of BaTiO₃ ceramics.The main results of this paper are as follows:1.The calculated lattice constant of BaTiO₃ is 4.027?,and the error with the experimental value is only 0.47%.The lattice constants of Ni,Mn,Cr,Co and Fe doped BaTiO₃ decrease successively,with a minimum of 4.015?.The lattice constants of Ru,Tc,Pd,Cu,Mo,Rh,Nb,Zn,Sc,Zr,Ag,Cd and Y doped BaTiO₃ increase in turn,with a maximum of 4.116?.2.The calculated enthalpies of formation of BaTiO₃ and Ba X_0.125Ti_0.875O₃ are all less than zero,indicating that they can be formed spontaneously.The enthalpy of formation of Fe and Zr doped BaTiO₃ is less than that of BaTiO₃(-4.163 e V/atom),which is easier to form than BaTiO₃;the enthalpy of formation of other Ba X_0.125Ti_0.875O₃ ceramics is larger than-4.163 e V/atom,which is more difficult to form than BaTiO₃ ceramics.The calculate binding energies of BaTiO₃ and Ba X_0.125Ti_0.875O₃ are all less than zero,indicating that their crystal structures are stable.The calculated binding energy of BaTiO₃ is-7.7941e V/atom.After Mo,Zr and Nb doping,the binding energy of BaTiO₃ decreases in turn,which enhances the stability of BaTiO₃ crystal structure;after doping V Tc,Cr,Sc,Mn,Ru,Fe,Y,Co,Rh,Ni,Pd,Cu,Zn,Ag and Cd,the binding energy of BaTiO₃ increases in turn and reduces the crystal structure stability of BaTiO₃.3.All BaTiO₃ has semiconductor characteristics.Among them,Sc,Ni,Y,Zr and Pd doped BaTiO₃ still shows the direct band gap semiconductor characteristics of barium titanate,and Co and Rh doping makes BaTiO₃ change into indirect band gap semiconductor characteristics.Doping V,Cr,Mn,Fe,Cu,Zn,Nb,Mo,Tc,Ru,Ag and Cd will make the band gap of BaTiO₃ disappear,enhance the conductivity and show semi gold properties.Among them,V,Cr,Nb,Mo and Tc doped BaTiO₃ is an n-type semiconductor with electrons as carriers,while Mn,Fe,Cu,Zn,Ru,Ag and Cd doped BaTiO₃ is a p-type semiconductor with holes as carriers.4.The density of states peaks of BaTiO₃ is mainly contributed by the orbital electrons of Ba-4d,Ti-3d and O-2p,the density of states peaks of Ba X_0.125Ti_0.875O₃ are mainly contributed by Ba-4d,Ti-3d,O-2p and X-3d(4d)orbital electrons.Before and after doping,Ba-O bond is ionic bond,and Ti-O bond is covalent bond.After doping atoms,the covalent bond interaction of the system will be enhanced and reduced,which is the reason for the enhancement and reduction of the stability of BaTiO₃ crystal structure.After doping Mo,Rh,Co,V,Pd,Ru,Fe,Cr,Tc and Mn atoms,BaTiO₃ can obtain magnetism,and the magnetic moment of doped barium titanate increases successively according to the order of atoms listed.The maximum magnetic moment of Mn doped BaTiO₃ is 3.48?_B.5.The calculated static dielectric constant of BaTiO₃ is 6.46.V,Zr,Sc,Nb and Y doping can reduce the static dielectric constant of BaTiO₃,while Rh,Cr,Co,Zn,Tc,Mo,Pd,Fe,Cd,Mn,Ag,Cu,Ni and Ru doping can increase the static dielectric constant of BaTiO₃.Y-doped BaTiO₃ has minimum static dielectric constant is 5.76 and Ru doped BaTiO₃ has maximum static dielectric constant is 88.45.Atomic doping can improve the dielectric properties of BaTiO₃.The doping of Sc,Zn,Y,Zr,Nb,Mo and Tc atoms can enhance the stability of the dielectric properties of BaTiO₃ ceramics to temperature.The incorporation of Mn,Fe,Ni,Cu,Zn,Mo,Tc,Ru,Pd,Ag and Cd atoms can improve the visible light response and optical properties of BaTiO₃.