Growth And Characterization Of Rare Earth Doped PZN-9PT Relaxor Ferroelectric Single Crystals

Perovskite structure relaxor ferroelectric single crystals Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃（PZN-PT）have been attracted much attention due to their high piezoelectric coefficient and electromechanical coupling coefficient near the morphotropic phase boundary（MPB）.However,the low Curie temperature and coercive field restrict their operating temperature range,temperature stability and high power service.In order to overcome these shortcomings,the rare earth ions Tm³⁺/Yb³⁺,Dy³⁺and Tm³⁺were doped into PZN-9PT crystals to improve their Curie temperature and coercive field.In addition,the phase structure,microstructure,and relaxation properties of the single crystals were studied.Especially,the photoluminescence properties and the physical mechanisms were investigated in detail.The rare ions(Tm³⁺/Yb³⁺,Dy³⁺and Tm³⁺)doped PZN-9PT crystals were grown by the high-temperature solution method.The XRD results show that the crystals are pure perovskite structure without second phase.The XRD diffraction peaks shift toward smaller angle,which indicates that the introduction of rare earth ions leads to an increase of lattice constants.SEM shows the typical step-by-step growth mode of the crystal.The electrical performance of crystals reveal that the Curie temperature of the PZN-9PT single crystals is increased by about 12.5℃-15℃ by introduction the rear ions Tm³⁺/Yb³⁺,Dy³⁺ and Tm³⁺,and the coercive field is increased by nearly 3-4 times.Using the fitting of Curie-Weiss law modified Curie-Weiss law,and Lorentz formula,it is found that the dielectric dispersion is increased in PZN-9PT crystals doped rare earth ions.The UV-VIS-NIR,UPL and DCL of crystals were measured by spectrophotometer and steady-state transient fluorescence spectrometer,respectively.The results show that the light absorption,down conversion and upconversion luminescence properties are induced in the PZN-9PT single crystals by the addition of the rare earth ions.Under a 980 nm laser excitation,the crystals modified by the Tm³⁺/Yb³⁺produce upconversion luminescence with three colors:blue（480 nm）,strong near-infrared（NIR,804 nm）and weak red（652 nm）.Under the 980 nm,388 nm/451 nm excitation,PZN-9PT:Dy³⁺crystals produce upconversion luminescence and down-conversion luminescence accompanied by blue light,green light and red light.Under the excitation of 800 nm and 464 nm laser,the up-conversion luminescence and down-conversion luminescence are realized in PZN-9PT:Tm³⁺crystals.These results provide a new insight for the design of multifunctional photoelectric materials.