Preparation And Characterization Of Ferroelectric Ternary Crystals PEN-PMN-PT

Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃（PMN-PT）crystals with composition in morphotropic phase boundary（MPB）region has been extensively researched due to their excellent electrical properties.However,low coercive field（E_C<3 kV/cm）and low Curie temperature（T_C<150℃）severely limit their applications at high temperature and in high-power devices.In the present work,the PEN with high Curie temperature was introduced to PMN-PT system,and a novel component PEN-PMN-PT was designed and grown.The morphology and phase structure of grown crystal were observed and analyzed through SEM and XRD,respectively.The growth mechanism of the crystal was explored by Wulff’s theorem and periodic bond chain theory.The dielectric,ferroelectric,absorption and luminescent properties of the crystals were tested by dielectric,ferroelectric and spectroscopic measurements.The main conclusions are as follows:PEN-PMN-PT crystals were successfully grown by the flux method for the first time.XRD measurements show that the crystals are pure perovskite structure and the components are located in the morphotropic phase boundary（MPB）region.Gauss fitting found that the content of the tetragonal phase increased with the increase of PEN content.The growth mechanism of PEN-PMN-PT crystal was investigated.The results show that PEN-PMN-PT crystals grow according to the layered mechanism and{100}is a thermodynamically stable natural exposure surface.Compared with traditional PMN-PT,PEN-PMN-PT crystals have higher Curie temperature and larger coercive field.Among four components,40PEN-13PMN-47PT crystal has the largest Curie temperature（T_c²91℃）and coercive field（E_C²6.81 kV/cm）,which means that PEN-PMN-PT crystal has potential applications at high temperature environment and in high-power devices.In addition,Curie-weiss fit shows that all crystals have good dispersion phase transition characteristics.Certain optical properties were induced for PMN-PT with the introduction of PEN.The absorption spectra show that there are seven strong absorption peaks in the UV-VIS-NIR region,all of which are characteristic absorption of Er³⁺.Under the excitation of 980 nm pump light source,PEN-PMN-PT crystals exhibit strong green and red up-conversion luminescence.By studying the dependence between pump power and fluorescence intensity,it is concluded that up-conversion luminescence is a two-photon interaction process.The study of fluorescence lifetime and quantum yield shows that 10PEN-54PMN-36PT crystal has the longest average fluorescence lifetime（τ_m¹67.32,52.16 us）and the largest quantum yield（QY⁰.0016%）at emission bands ⁴S_3/2→⁴I_15/25/2 and ⁴F_9/2→⁴I_15/2....