Study About Adsorption And Diffusion Of Hydrogen On PbTiO₃ Surface With Poin Defect

Lead titanate(PTO)is a kind of typical perovskite ferroelectrics.It has widespread used in medical,military,aerospace and other cutting-edge fields based on its good piezoelectric,ferroelectric and optical properties.Meanwhile it possessed advantages of large residual polarization,high phase transition temperature and low dielectric constant.On account of the excellent piezoelectric properties of PTO,it has been widely used in the manufacture of ultrasonic oscillators and detectors.At the same time,because of the excellent pyroelectric effect of high density and high strength PTO ceramics,infrared sensors could be prepared by PTO ceramics.However,during in the preparation of PTO,point defect occures inevitably.Moreover,impurity doping and defect could modulate the porperty of PbTiO3.Nitrogen doping may be a sort of potential P-type doping element,which is similar to the radius of oxygen atom.In conclusion,it is necessary to reserach N-doped andO-vacancy in PbTiO3.In view of the broadly existence of hydrogen in various working environments,adsorption and diffusion of hydrogen on N-doped and O-vacancy lead titanate surfaces are studied by using CASTEP software package.The following conclusions are drawn:On the surface of PbTiO3,the doping energy of N-doped O(1)is 0.0938 e V different from that of N-doped O(2).At the same time,the stability of PbTiO3 system with O(1)vacancy is as well as that PbTiO3 system with O(2)vacancy.The adsorption of hydrogen atom on the surface of PbTiO3 belongs to chemical adsorption.Compared with the defective surface of PbTiO3(001),H atoms are more likely to adsorb on the defective surface of PbTiO3(100).When nitrogen atom substitutes for the site of O(2),H atom will adsorb on nitrogen atom,the adsorption energy is 5.8611 e V.In other cases,H atoms are adsorbed on O atoms.In the process of H diffusion on the PbTiO3(001)surface with N-doped,there is a potential well at 0.15 nm below the first O-Pb layer.When hydrogen atoms diffuse on the surface of PbTiO3 with point defect,the point defect at the O(2)position is more helpful diffusion of hydrogen than that at the O(1)position on the surface of PbTiO3(001).Point defects at the O(1)position are more conducive to hydrogen diffusion than the O(2)position on the surface of PbTiO3(100).