Study On The Structure Control And Luminescence Properties Of Rare Earth（Pr/Er/Dy）Doped LaInO₃ Phosphors

At present,almost 20%of energy consumption is used for lighting in the world.Researchers have shown great interest in the exploration of lighting materials with the increasing demand for energy saving and environmental sustainability.Rare earth luminescent materials play a vital role in the new solid-state light source-white light emitting diodes（WLEDs）.Currently,the widely used WLED is made by coating YAG:Ce phosphor on In Ga N chips.However,WLED devices have high correlated color temperature（CCT）and low color rendering index（CRI）due to the lack of red light emission in the emission spectrum of YAG:Ce phosphors.In addition,devices that generate white light by coating red-green-blue phosphors（RGB-LED）on In Ga N chips have low luminous efficiency due to re-absorption among multiple luminous centers.The above-mentioned problems can be avoided by coating single-phase white phosphors on blue LEDs to prepare WLEDs.Host-sensitized rare earth ion emission is one of the important methods for preparing high-efficiency single-phase white phosphors.Currently,researchers have a consensus on the energy transfer of host-sensitized energy transfer.They believe that the host absorbs and transfers the excitation energy to the activator,causing the latter to emit light.However,researchers are still unclear on the energy transfer mode,exciton behavior and the mechanism of how to affect the luminescence properties of the material in the host-sensitized energy transfer,which restricts the development of new high-efficiency fluorescent materials and the application of WLED devices.Therefore,clarifying the energy transfer dynamics process of the host-sensitized rare earth ions luminescence will have very important guiding significance for the development of new and efficient luminescent materials.In this work,try to realize the white light emission of single-phase phosphors,to explore the effect of rare earth ion doping on the crystal structure of the material,to explore the relationship between structural distortion and luminescence performance,and to focuse on the energy transfer process of host-sensitized rare earth ion luminescence,three single-phase phosphors,LaInO₃:Pr³⁺,LaInO₃:Er³⁺and LaInO₃:Dy³⁺were synthesized via solid-phase reaction method.The main results are as follows:（1）The LaInO₃ host material is synthesized by high temperature solid reaction method.Structural characterization shows that a pure phase sample was prepared.Ultraviolet-visible absorption spectroscopy test indicates that LaInO₃ has three different host absorption bands with a band gap of 3.51 e V.Fluorescence spectroscopic test indicates that LaInO₃ host material can be self-activated to produce broadband blue light emission.The emission spectrum was tested after the sample annealed with oxygen,and the emission intensity remained basically unchanged.The peak shape and peak position of the excitation spectrum tested under different wavelength conditions remain consistent.The decay lifetime can be obtained to be 740 ns by testing and fitting the fluorescence lifetime decay curve.（2）The LaInO₃:Pr³⁺phosphor is synthesized by high temperature solid reaction method.Structural characterization shows that a pure phase sample was prepared.The structure refinement results show that with increasing the Pr³⁺doping level,the cell parameters a,b and c decrease,and the lattice shrinks.When excited by the host absorption wavelength of 275 nm,LaInO₃:Pr³⁺phosphor can produce single-phase white light emission,and the white light CIE coordinates is（0.3355,0.3742）.（3）The LaInO₃:Er³⁺phosphor is synthesized by high temperature solid reaction method.Structural characterization shows that a pure phase sample was prepared.The structure refinement results show that with increasing the Er³⁺doping level,the lattice shrinks,the cell parameters a and b decrease,while c increases.The infrared absorption band produces red shift,and the Raman band produces red shift and blue shift.X-ray photoelectron spectroscopy test shows that Er element exists in+3 valence state.Using the host-sensitized luminescence mechanism,the emission color of LaInO₃:Er³⁺phosphor can be adjusted from dark blue to light blue when excited at a wavelength of 328 nm.When the Er³⁺ion 4f-4f transition wavelength is excited,the green light emission intensity dominates the spectrum.With increasing the Er³⁺doping level,the ratio of red light to green light emission intensity increases from 0.1 to 0.9.When excited by the charge transfer state wavelength between Er³⁺and O^2-,the red emission intensity of LaInO₃:Er³⁺exceeds the green emission intensity,and the color of the phosphor can be adjusted from green to red.With increasing the doping level,the ratio of red light to green light emission intensity increased from 0.9 to 4.7,and the lifetime of red light emission was significantly reduced.（4）The LaInO₃:Dy³⁺phosphor is synthesized by high temperature solid reaction method.Structural characterization shows that a pure phase sample was prepared.The structure refinement results show that with increasing the Dy³⁺doping level,the lattice shrinks,the cell parameters a,b,and c decrease,the In-O₁-In bond angle increases,and the degree of lattice distortion decreases.X-ray photoelectron spectroscopy test shows that Dy element exists in+3 valence state.Using the host-sensitized luminescence mechanism,the emission color of LaInO₃:Dy³⁺phosphor can be adjusted from dark blue to white when excited at a wavelength of 328 nm,and the white light CIE coordinates is（0.3474,0.3422）.With increasing the Dy³⁺doping level,the decay lifetime and emission intensity of the host decrease.The energy transfer efficiency of host sensitization is as high as 77.2%.