Preparation And Properties Of Eu-doped PMN-PT Transparent Piezoelectric Ceramic

The molecular formula of relaxed ferroelectric lead niobium-magnesite-lead titanate is（1-x）Pb(Mg_1/3Nb_2/3)O₃-x Pb TiO₃,abbreviated as PMN-x PT.It has been widely used in ultrasonic imaging,seabed mapping,nondestructive testing and pressure sensors.In recent years,the piezoelectric and light transmittance properties of PMN-x PT based materials have been greatly improved by means of rare earth element doped and AC polarization,so that such materials have a wider application prospect and become the research focus of ferroelectric materials again.Piezoelectric materials with high piezoelectric properties and high transmittance have opened a door to the development of powers-electro-optical multifunctional couplers,which have attractive application prospects in transparent piezoelectric touch sensors,photoacoustic imaging transparent transducers,transparent drivers and other intelligent devices and medical imaging.However,the preparation of piezoelectric ceramics with both high piezoelectric properties and high transmittance has always been a great challenge.In this paper,the Eu-doped PMN-28PT transparent piezoelectric ceramics with high transmittance and high piezoelectric properties were firstly prepared,which will greatly promote the application of PMN-x PT ceramics in the transparent piezoelectric field.Then,the electrical properties and microstructure of the prepared ceramics were comprehensively characterized,and the domain structure of 2.5 mol%Eu doped ceramics was further explored,the relationship between different domain structure of piezoelectric and transparent properties was analyzed.Finally,the effect of polarization mode on piezoelectric properties and transmittance was investigated.The main conclusions are as follows:1.PMN-28PT transparent piezoelectric ceramics with different Eu doped content（0,1,2,2.5,3 mol%）were prepared.The addition of Eu makes the intercrystal bonding stronger,and the fracture mode changes from an intergranular into a transgranular,which is more conducive to the densification of ceramics and the improvement of light transmittance.With the increase of Eu doped,the piezoelectric properties and transmittance firstly increase and then decrease.The piezoelectric coefficient d₃₃of 2 mol%and 2.5 mol%Eu doped was greater than 1400 pC/N,but the transmittance of 2.5 mol%Eu doped was the highest,reaching 66%at 900nm wavelength.Overall,Eu doped 2.5%performs best.2.The electric domain structure of 2.5mol%Eu doped PMN-28PT transparent piezoelectric ceramics was observed by SEM and PFM.In this ceramic,the domain structure mainly includes two kinds of domain configuration,namely watermarks and parallel stripes domain.The average size of the dominant watermarks domain is250nm,which is far below the lower limit of transmittance,so it is beneficial to the transmittance of visible light region.PFM strain loop test shows that the switch of parallel stripes domain is more sensitive to electric field and causes a large strain change,so the structure of parallel stripes domain plays an important role in improving piezoelectric response.3.AC polarization of 2.5 mol%Eu doped PMN-28PT transparent piezoelectric ceramics was studied.The piezoelectric coefficient d₃₃is similar to that of DC polarization,and the polarization speed of AC polarization is faster than that of DC polarization.In terms of transmittance,since DC polarization generally reduces the transmittance of ceramics,it is of great significance to explore whether AC polarization can maintain or improve the transmittance of ceramics.At present,DC polarization has a negative impact on the transmittance of ceramics.However,due to many factors affecting AC polarization,further exploration is needed.