Study On Nanoindentation Technology And Crack Tip Deformation Field Experimental Of Ternary Ferroelectric Single Crystal PIN-PMN-PT

Ternary Ferroelectric Single Crystal Gallium Indium Lead–Magnesium Pyromanganate–Lead Titanate(Pb(In_1/2Nb_1/2O₃)–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃,PIN-PMN-PT),as New Type of Iron Electric single crystal has become a popular research object in the field of functional materials.Its application range is wide and it is used to regard as important materials in electromechanical devices such as ultrasonic transducers,actuators and sensors.Because of the uncertainty of ferroelectric single crystal in the process of processing and use,resulting in material defects,fracture,and so on,the electromechanical device failure.Therefore,it is great significance that studing the mechanical properties of ferroelectric single crystals and the evolution of the micro-nano scale deformation field at the crack tip are to improve the reliability and lifetime evaluation of ferroelectric single crystal devices.In this paper,the mechanical properties of ternary ferroelectric single crystal were studied by using nanoindentation technology,and the initiation,propagation and crack deformation field of the material cracks were studied by field emission in situ scanning electron microscopy and geometric phase analysis methods.The conclusion is:1.With the nanoindentation technology,hardness,elastic modulus and contact stiffness were measured on the three crystal faces of PIN-PMN-PT,and the elastic recovery rate of each crystal plane was calculated,the results show:?1?The hardness of the?001?crystal plane is 6.07 GPa,the?110?crystal plane is 6.81GPa,and the?111?crystal plane is 6.91 GPa.Therefore,the hardness of the?111?crystal plane of the material is greater than that of the other two crystal planes.The hardness of the?110?crystal plane is greater than that of the?001?crystal plane.?2?The elastic modulus of the?001?crystal plane is 132.55GPa,the?110?crystal plane is 137.80GPa,and the?111?crystal plane is 138.53GPa.Therefore,the elastic modulus of the?111?crystal plane of this material is greater than that of the other two crystal planes.The?110?crystal plane is greater than that of the?001?crystal plane.?3?The change law of contact stiffness is a linear relationship with the depth of penetration as a whole,with the increase of depth of penetration,the greater the length and width of the crack,the?111?crystal plane is slightly larger than the other two planes?110?.The crystal plane is the next,the?001?crystal plane is the smallest.?4?By calculating the elastic recovery rate,the elastic recovery rate of the?001?crystal plane is the highest when pressed in the same depth,followed by the?110?crystal plane,and the?111?crystal plane is the smallest.It is concluded that the elastic recovery rate is higher and the hardness and elastic modulus are smaller.?5?With the depth increases,the residual stress inside the material decreases.All the forces of the indenter acts on the plastic deformation,the hardness value and the elastic modulus value decrease gradually,and the size effect is obvious at the microscopic level.2.The deformation field of the crack tip was calculated by using the single-axis tensile test and the GPA method.And the variety of strain field in the micro-nano scale of the dynamic crack tip in a ternary ferroelectric single crystal was analyzed.Get the following conclusions:?1?When the load gradually increases to 2.34?m,cracks occur in the prefabricated notch,and as the load continues to increase,the crack gradually expands,basically extending along a direction perpendicular to the tensile direction,and no other cracks are generated,proving that the material matrix is free from defects.?2?For different crack lengths,the strain field average strain value at the crack tip changes around 1%.Among them,the positive strain and shear strain values are small and basically approach zero.The positive strain is mainly used to control the change of the strain field.The crack belongs to type I crack.?3?The image calculated by the GPA method shows that there is a high-strain emission region at the prefabricated notch,and the generated portion is consistent with the position where the crack appears,and the orientation of the crack does not change.