Study On Structure And Properties Optimization Of Relaxor Ferroelectric Single Crystal PZN-7PT

Relaxationferroelectricsinglecrystal0.93Pb(Zn_1/3Nb_2/3)O₃-0.07Pb Ti O₃has a wide range of application prospects in the fields of sensors and transducers due to its excellent piezoelectric properties.It has become a hotspot material in the field of piezoelectric research and has attracted wide attention from researchers around the world.However,due to the limitation of the growth and polarization technology,the coercive field and the piezoelectric coefficient of each single crystal are different.The coercive field size,the tripartite phase transition temperature and the Curie temperature are the main factors affecting the practical application of the single crystal.Therefore,it is of great scientific significance and application prospect to study the performance optimization and structure of relaxation ferroelectric single crystal PZN-PT.In this paper,PZN-7 PT crystals were successfully prepared by high temperature solution method.The properties of PZN-7PT crystal were optimized by annealing and polarization.The ferroelectric,dielectric and piezoelectric properties of the optimized samples were studied.It was found that the coercive field Ec of the optimized samples was 28%higher than that of the non-optimized samples.The piezoelectric coefficient d₃₃in the（001）direction is increased by 34%.The tripartite-tetragonal phase transition temperature increased from 108℃to 139℃.By fitting the relaxation at different test frequencies,it is found that the optimized sample has better relaxation.Combined with the single crystal XRD test results,it is proved that the prepared sample has high crystallinity.In situ Raman spectroscopy study of optimized PZN-7PT samples during the polarization process,it is found for the first time that there is a dependence between the intensity of the Raman spectrum signal and the polarization electric field.When the polarized electric field is less than the double coercive field,the intensity of Raman spectral signal decreases with the increase of the polarized electric field.When the polarization electric field is greater than the double coercive field,the intensity of Raman spectrum signal increases with the increase of the polarization electric field,and finally does not change.Among the seven Raman peaks of the PZN-7PT crystal including 73cm^-1,137cm^-1,177cm^-1,268cm^-1,419cm^-1,596cm^-1,783cm^-1,the two Raman peaks of 137cm^-1and 268cm^-1,representing the degree of short-range arrangement of perovskite BO₆structures,shifted first to red and then to blue.It shows that the short-range symmetry of the structure decreases with the increase of the electric field when the polarization electric field is less than twice coercive field,and increases with the increase of the electric field intensity when the polarization electric field is greater than twice coercive field,and finally remains unchanged.These results indicate that the ferroelectric,dielectric and piezoelectric properties of PZN-7PT crystals can be changed by optimizing their properties.In particular,the discovery of the special phenomenon that the intensity of the Raman spectrum signal of PZN-7PT is dependent on the magnitude of the polarization electric field has important reference significance for further understanding of the properties of PZN-7PT crystals and exploring their crystal preparation and application.