Electrical And Optical Properties Of Rare Earth Ion-doped PZN-PT Crystals

Recently,Pb(Zn_1/3Nb_2/3)O₃-Pb TiO₃?PZN-PT?relaxor ferroelectric single crystals have been widely studied due to its excellent piezoelectric,dielectric performance,and electro-induced strain characteristics.These remarkable properties make PZN-PT single crystals a promising material for electroacoustic device applications,such as underwater sonar,sensors,medical imaging devices,etc.However,PZN-9PT single crystals show the relatively low Curie temperature?T_c?170??and coercive field?E_c?3.5 k V/cm?,it is not suitable for use in high-power applications and high temperatures working environment,and its weak optical performance also limits its applications on optical devices.In this paper,rare earth ions Eu³⁺and Sm³⁺were introduced into the PZN-PT crystals,and Pb(Er_1/2Nb_1/2)O₃?PEN?was dissolved into the PZN-PT crystals to form a new materials system PEN-PZN-PT,which is expected to improve the Curie temperature,coercive field of the crystals.Meanwhile,the phase structure,micro and macro structure and photoluminescence properties of the crystals were characterized.The Eu³⁺,Sm³⁺doped PZN-9PT crystals and 15PEN-63PZN-22PT,15PEN-67PZN-18PT and22PEN-50PZN-28PT crystals were grown by the flux technique.The grown crystals have a pure perovskite structure,rare earth ions diffused well into the PZN-PT crystals to form a solid solution.The SEM showed that the crystals'growth mode was layered growth.Electrical performance results show the coercive field of the PZN-9PT crystals was increased by nearly three and seven times due to the addition of rare earth ions Eu³⁺and Sm³⁺,respectively.The Curie temperature of the PEN-PZN-PT is 234-285?,which is higher than that of 64-115?compared to the PZN-PT system?T_c?170??.The parameter?_Aof the PZN-PT:Eu crystals are56.37,56.76,58.05,and 58.61 K,and the parameter?_Aof the PZN-PT:Sm crystals are 34.08,34.08,34.12,and 34.81 K at 1 k Hz,10 k Hz,100 k Hz and 1 MHz,respectively.It is found through the fitting of relaxation characteristic that the incorporation of rare earth ions can significantly improve the phase dispersion of PZN-PT crystals.PZN-9PT:Eu crystals emit green?593 nm?,yellow?613 nm?,and red?657 and 716 nm?light at 464 nm laser excitation,corresponding to the transition of ⁵D₀?⁷F_J?J=0,1,2,3,4?of Eu³⁺.As the temperature increases from 298 to 393 K,the intensity of all emission peaks decreases monotonically.PZN-9PT:Sm crystals emit blue-green light?486 nm?,green light?566 nm?,and red light?649 nm?at 315 nm laser excitation,corresponding to the energy level transitions of ⁴H_11/2?⁶H_5/2?⁴G_5/2?⁶H_5/2?⁴G_5/2?⁶H_11//2.PEN-PZN-PT crystals emit green?527 and 563 nm?and red?680 nm?light when excited by 980 nm laser,corresponding to Er³⁺from the excited state energy levels²H_11/2,⁴S_3/2and ⁴F_9/2to the ground state level ⁴I_15/2.