Synthesis And Spectral Properties Of Several Rare Earth Ions Doped New Luminescent Materials For White LEDs

White light-emitting-diodes have been widely used in lighting and display area,due to its advantages of energy-savings,environmental friendliness,color-tunable,etc.Phosphor as the main component of pc-WLEDs obtained great attention and had become a focus.However,the phosphors which can meet the requirements of commercial WLEDs are rare.Thus,it is of great value to develop novel phosphors which can be efficiently excited by UV or blue light.In this paper,rare earth borate,niobium?tantalate?and tungstate phosphors were synthesized by high temperature solid phase method,and their luminescence properties were investigated.The specific research contents are as follows:1.K₃YB₆O₁₂:Ce³⁺/Tb³⁺,K₃YB₆O₁₂:Bi³⁺,Eu³⁺and K₃YB₆O₁₂:Sm³⁺were synthesized using K₃YB₆O₁₂ as matrix.The structure,luminescence properties,fluorescence life,concentration quenching mechanism and energy transfer mechanism were analyzed and discussed.K₃YB₆O₁₂:Ce³⁺,Tb³⁺phosphorsupon near-ultraviolet excitation?³65 nm?,the tunable emission-color from blue to green can be realized in the as-prepared phosphors.The critical distance,efficiency,and mechanism of Ce³⁺?Tb³⁺energy transfer are also calculated and determined according to theoretical formulas.The Bi³⁺?Eu³⁺energy transfer phenomenon was induced in the K₃YB₆O₁₂:Bi³⁺,Eu³⁺phosphors that resulted in broad excitation characteristic in ultraviolet region.With the Eu³⁺contents increase,the Bi³⁺?Eu³⁺energy transfer becomes more and more efficient that leads to the color-tunable emission from ultraviolet-blue to red.In addition,the efficiency and mechanism of Bi³⁺?Eu³⁺energy transfer were also investigated in detail.K₃YB₆O₁₂:Sm³⁺phosphorsupon excitation with 403nm,the phosphors emitted orange-red emission.The optimal doping concentration of Sm³⁺ions in K₃YB₆O₁₂ was about 0.05.These results showed that K₃YB₆O₁₂:Ce³⁺/Tb³⁺,K₃YB₆O₁₂:Bi³⁺/Eu³⁺and K₃YB₆O₁₂:Sm³⁺phosphors have potential application prospects in the near ultraviolet excited white LED.2.NaKLaNbO₅:Eu³⁺NaKLaNbO₅:Dy³⁺and NaKLaMO₅:Sm³⁺?M=Nb,Ta?phosphors were synthesized by high temperature solid phase method.The crystal structure,spectral properties,microstructure,quantum efficiency and thermal stability of the synthesized material were studied.Upon excitation with blue light?464 nm?,the phosphor KNaLa_0.8Eu_0.2NbO₅ with optimized composition presented orange-red emission at 606 nm,the optimum doping concentration is 20%.By employing NaKLa_0.8Eu_0.2NbO₅ phosphor as orange-red component,a white LED device with appropriate correlated color temperature?CCT?of 5712 K,and high color rendering index?CRI?of 83.2 was fabricated.The optimum doping concentration of Dy³⁺was found to be about x=0.05 for NaKLa_1-xDy_xNbO₅ phosphors,and the critical distance of energy transfer among Dy³⁺ions was calculated to be 17.45?.The decay lifetime of Dy³⁺was very short?<1 ms?.In addition,the temperature-dependent emission spectra were also investigated.NaKLaMO₅:Sm³⁺?M=Nb,Ta?phosphors can be excited by near uv?406 nm?,emitting red light at 664 nm,the optimal doping concentration of Sm³⁺was found to be 0.03?3 mol%?.As to NaKLa_0.97Sm_0.03Ta_1-xNb_xO₅ series,with the Nb⁵⁺-contents?x?increase,the emission intensity gradually increased up to the complete replacement of Ta⁵⁺by Nb⁵⁺.So,among all as-prepared phosphors,the phosphor NaKLa_0.97Sm_0.03NbO₅ has the optimal luminescence performance,and its internal quantum efficiency,CIE coordinates,and temperature-dependent luminescence properties were investigated in detail.The results showed that NaKLaNbO₅:Eu³⁺NaKLaMO₅:Sm³⁺?M=Nb,Ta?could be used as red luminescent material for white LED,and NaKLaNbO₅:Dy³⁺could be used for yellow luminescent material.3.Alkali metal ion substitution is an effective strategy to improve the luminescence properties of phosphors.In this work,a series of red-emitting phosphors Na_1-xLi_x/2K_x/2La_0.6Eu_0.4MgWO₆ were prepared by a traditional hightemperature solid-state reaction.Their phase structure,microstructure,luminescence properties and potential application in phosphor-converted white light-emitting diodes?pc-WLEDs?were investigated in detail.Photoluminescence investigation indicated that the partial substitution of Li⁺/K⁺ions for Na⁺ions improved largely the red emission of Eu³⁺.With near ultraviolet chip to Na_0.7Li_0.15K_0.15La_0.6En_0.4MgWO₆ for red light components,mixed commercial blue/green phosphor powder preparation of LED device CIE?0.3045,0.3354?,CCT is 6911 K,CRI is79.5.The results indicated that the optimized red phosphor in this work could be a potential candidate for WLEDs pumped by NUV chips.