Growth And Characterization Of Er³⁺/Ho³⁺/Yb³⁺ Modified PSN-PMN-PT Crystals

Ferroelectric single crystals Pb(Sc^1/2Nb^1/2)O₃-Pb(Mg^1/3Nb^2/3)O₃-PbTiO₃（PSN-PMN-PT）attract much attention from researchers due to excellent ferroelectric,piezoelectric,pyroelectric and electrostrictive properties.However,weak optical properties limit their applications in colour displays,optical data storages,short-wavelength lasers and optoelectronic couplers.In present work,Er³⁺,Ho³⁺ and Yb³⁺ ions were introduced into crystal lattices to achieve outstanding optical performance by means of their luminescence in crystal field.The effects of rare earth ions on crystal structure and electric properties were also investigated.Growth mechanism of crystals was analyzed additionally.PSN-PMN-PT,Er³⁺,Ho³⁺,Er³⁺/Yb³⁺and Ho³⁺/Yb³⁺modified PSN-PMN-PT crystals were grown by using the flux method.The results from X-ray diffraction（XRD）indicated that all crystals were pure perovskite phase structure.No any impurity phase or secondary phase was detected,but lattice distortion was produced as rare earth ions were introduced into crystal lattice.The analysis from SEM revealed typical layer growth mechanism,but another mechanism of bridging growth was also observed in Er³⁺ modified crystals.The higher phase transition temperature from ferroelectric phase to paraelectric phase（TF-P¹69 ℃）was obtained for ternary PSN-PMN-PT crystals,which overcomes the disadvantages of low phase transition temperature of PMN-PT（TF-P¹50 ℃）.The dielectric permitivity of PSN-PMN-PT crystals increased from 2389 to 3180 with Ho³⁺/Yb³⁺modification,and dielectric loss decreased by 0.7%.The minimum value of piezoelectric coefficient along optimal direction was 1740 pC/N for Er³⁺ modified PSN-PMN-PT crystals.Special absorption at visible and near-infrared band was induced for crystals with rare earth ions modification.Upconversion luminescence from infrared light to green and red light was observed under 980 nm excitation.As addition of Yb³⁺ions,the luminescence intensity increased by one and three order of magnitude for Er³⁺ and Ho³⁺ modified crystals,respectively.The absorption cross-section,corresponding to the biggest absorption peak of Er³⁺ and Ho³⁺modified crystals（654 nm and 643 nm respectively）,increased from 9.82×10^-21cm²and7.067×10^-21 cm² to 1.17×10^-20 cm² and 1.13×10^-20 cm²,respectively.The addition of Yb³⁺increased the mean fluorescence lifetime of 4S3/2?4I15/2 emission from 53.05 μs to 98.07 μs for Er³⁺modified crystals,and enhanced the quantum yield from 0.0048% to 0.015%.The results provide an effective way for exploiting optical properties of relaxor ferroelectric crystals,and offer an experiment support for further study in optical and photoelectric coupling performance of the materials.