Performance And Mechanism Of Complex Multicomponent Lead Based Piezoelectrics

Piezoelectric ceramics were commonly applied in many fields,such as sensors,actuators,and transducers,as a functional material that can transform the energy between mechanics and electricity.Perovskite materials possess favorable piezoelectric performance and are the most commonly applicated ferroelectric materials,such as Pb(Zr,Ti)O3(PZT).Due to the lack of species in highperformance piezoelectrics,the design of new high-performance piezoelectrics can boost the development of piezoelectrics.Considering the large induced random field in complex multicomponent systems,this thesis designed five types of complex multicomponent lead-based piezoelectrics and systematically studied the properties of ferroelectricity,piezoelectricity,and dielectricity.In the meantime,it also exposed the correlation between the performance,structure,and mechanism of complex multicomponent lead-based piezoelectrics via in-situ high energy X-ray diffraction,aberration-corrected scanning transmission electron microscopy(acSTEM),and the First principle calculations.At first,a new high-performance piezoelectric ceramic,PNNPb(In0.5Nb0.5)O3-PT-Pb(Yb0.5Nb0.5)O3(PNN-PIN-PT-PYN),was designed based on the classical piezoelectric ceramic Pb(Ni1/3Nb2/3)O3-PbTiO3(PNN-PT).The piezoelectric coefficient is 1000 pC/N around the MPB,which is far larger than the commercial PZT ceramic.Based on the result,this thesis proposed a new design method to design high-performance piezoelectrics via the high entropy method.Following this design method,this thesis designed another new high-performance piezoelectric,PN-N-Pb(In0.5Nb0.5)O3-PT-Pb(Sc0.5Nb0.5)O3(PNN-PIN-PT-PSN)and the piezoelectric coefficient is above 1000 pC/N.The domain structure turns out to be the irregularly distributed nano domain structure,originating from the breaking of long-range ferroelectric order by poly elements and resulting in high piezoelectric performance.The result of in-situ high-energy X-ray diffraction also demonstrates that the rotation of flexible polarization can boost the intrinsic lattice strain,leading to high piezoelectric performance,suggesting the effectiveness of this design method.The third complex piezoelectric system,PNN-Pb(In0.5Nb0.5)O3-PbZrO3-PT(PNN-PIN-PZ-PT),was also designed,the piezoelectric coefficient of which is also above 1000 pC/N.Via ac-STEM,it was found that the polarizations in the material can orientate equally in all directions.These polarizations possess high flexibility,and they can be detected in the large region of the grains.The first-principles calculations also revealed that this polarization configuration originates from the multielement doped and is the cause of high performance,demonstrating the effectiveness of the high entropy method again.Then,the doping of Sm in the PNN-PIN-PZ-PT was then researched.The segregation of Sm in the matrix leads to endotaxial nonpolar nano precipitations,which can eliminate the hysteresis of electrostrictive strain.In the Sm-doping PNNPIN-PZ-PT system,the matrix can produce high strain under a low stimulated electric field,and the endotaxial nonpolar nano precipitations can provide a strong restoring force to eliminate the hysteresis.Thus Sm-PNN-PIN-PZ-PT possesses favorable electrostriction properties,which can be applied to many micro displacement devices.At last,a more complex multicomponent piezoelectric system,Pb(Mg0.3Ni0.7)1/3Nb2/3O3-Pb(In0.7Yb0.3)0.5Nb0.5O3-Pb(Zr0.1Ti0.9)O3(PMNN-PIYNPZT)was also studied to explore the effect of high entropy method to the components with higher than five species elements in B site.The piezoelectric performance of PMNN-PIYN-PZT is larger than simple piezoelectric systems,such as PNN-PT,suggesting that the high entropy method is effective in the design of high-performance piezoelectrics.Based on the perovskite piezoelectrics,this thesis systematically studied the performance and mechanism of complex multicomponent lead-based piezoelectrics.This thesis proposes new methods to design high piezoelectric and electrostrain materials,and boosts the development of high-performance materials in these fields.