Domain Structures And Piezoelectric Properties Of PMN-xPT Single Crystals

Ferroelectric materials have many functions,such as sensing,driving and so on,and have been widely used in electro-machanical,aerospace and other fields.Recently,PMN-PT has attracted the attention of many researchers because of its dielectric,electrostrictive,piezoelectric effects and other properties.Pb(Mg1/3Mb2/3)O3-x Pb Ti O3(PMN-x PT)crystals are one of the most typical relaxor ferroelectric crystals.PMN-x PT is a complex solid solution formed by the mixing of PMN and PT,and structural phase transition will occur in the crystal with the change of ratio x in PT,causing a big difference in performance.It is thus clear that the macro-properties of crystals are closely related to their microscopic domain structures.Obviously,the research on the domain structures of ferroelectric crystals makes it easier to understand the internal mechanism of crystal and the influence of domain structures on microscopic physical properties,it is of great significance and reference to improve the piezoelectric properties of materials and the design of lead-free Piezoelectric Materials.This paper has systematically studied the surface ferroelectric,dielectric,electromechanical,and domain structure properties of three components: PMN-0.25 PT,PMN-0.28 PT and PMN-0.36 PT.The phase transition temperature and the coercive field at different temperatures are determined by dielectric and ferroelectric experiments.The polarization of the electric field along the crystal [001]C direction is treated by using different polarization electric fields in the coercive field.Observe the change of domain structure after polarization by using polarizing microscope,test out the corresponding electromechanical coefficients and thus understand the difference of electromechanical coefficients under different polarization conditions.Analyze the effects of different domain shapes and sizes on the mechanical and electrical properties by connect the domain structure with mechanical and electrical properties.Then change the temperature of the crystal and observe the change of domain structure with temperature,especially the phenomenon near the phase transition temperature and the behavior of crystal at the phase transition point.In addition,for the PMN-0.25 PT crystal,besides the(001)plane,the domain structures and properties of the other two planes(011)and(111)have been studied,and the difference of domain structure and mechanical and electrical properties between the same component crystals in different directions is compared.In the end,for the PMN-0.25 PT crystal,use the high temperature polarization technique along the [100]C direction,and during the polarization process observe the response of domain structure to electric field and temperature along the [100]C direction.Change the polarization temperature and electric field condition,control domain structure,optimize crystal performance.The results of this paper advance the study of the relation between PMN-PT domain structure and macroscopic properties,and provid the experimental method and basis for optimizing the performance of PMN-PT single crystal.