Synthesis And Luminescence Properties Of Tungstate And Titanate Phosphors

White LED?Light Emitting Diode?is known as a new generation of green light source and is used in the field of solid-state lighting because of its excellent luminous performance,high electro-optic conversion efficiency and environmental friendliness.The traditional lighting sources?general energy-saving lamps,halogen lamps and incandescent lamps?have large power consumption,and their performance can no longer meet the needs of users for high-quality lighting.At present,the preparation of white LEDs mainly uses the combination of blue In Ga N chips and commercial yellow phosphors(YAG:Ce³⁺).The principle is that part of the blue light generated by the electrical excitation acts on the yellow phosphor to excite it to produce yellow light,while the other part of the blue light that does not participate in the excitation is mixed with the emitted yellow light to form white light by adjusting the ratio of the two.There are also three-primary phosphors?red,green and blue?that generate white light under the excitation of an ultraviolet/near-ultraviolet chip,but after a long period of illumination,harmful ultraviolet radiation can be generated.In these two methods of realizing white LEDs,red phosphors are extremely important,and the lack of red phosphor will lead to poor color rendering index of the former and inefficient light emission of the latter.This article focuses on new type of red?orange-red?phosphors.Tungstate and titanate with double perovskite structure are excellent matrix materials for preparing phosphors.Tungstate has a self-luminous phenomenon and has a broadband emission peak.For doped Sm³⁺or Eu³⁺,tungstate can generate a strong and broad matrix excitation band in the near ultraviolet region?350?450 nm?.Titanate is also a potential phosphor matrix material because of its excellent stability and luminescent properties.In addition,the new type of A₂BTi O₆ double perovskite material is also a hotspot in the current field of materials research.Based on the above two materials,we prepared new Sr₉La₂W₄O₂₄:x Sm³⁺,y Eu³⁺series phosphors and Gd₂Zn Ti O₆:x Sm³⁺,y Dy³⁺series phosphors,then the research progress is as follows:1)For the first time,Sr₉La₂W₄O₂₄:Sm³⁺orange-red phosphor with double perovskite structure was synthesized by high temperature solid phase method.XRD results indicate that Sm³⁺ions successfully replaced La³⁺ions and were incorporated into Sr₉La₂W₄O₂₄ material,maintaining the original tetragonal crystal system structure of the material.Through SEM analysis of the growth morphology of the phosphor,it is found that the particle size is between tens of nanometers and one micrometers.Under the excitation of 407 nm,the strongest emission peak is located at 602 nm,and the optimal doping concentration of Sm³⁺ion is 15%,and the concentration quenching is due to the electric dipole-electric dipole interaction.For the Sr₉La₂W₄O₂₄:x Sm³⁺,y Eu³⁺co-doped phosphors prepared by high-temperature solid-phase method,the energy transfer from Sm³⁺to Eu³⁺was confirmed.2).For the first time,the high-temperature solid phase method was used to prepare double perovskite Gd₂Zn Ti O₆?hereinafter abbreviated as:GZT?series phosphors including GZT: successfully replaced Gd³⁺and were incorporated into monoclinic Gd₂Zn Ti O₆ materials.SEM analysis showed that the morphology of the GZT series samples emerge a short rod-like structure with a diameter of about 5 microns.GZT:x Sm³⁺phosphor emits 602 nm orange-red light under the excitation of 407 nm,and the optimal doping concentration of Sm³⁺ion is 3%;The GZT:y Dy³⁺phosphor produces a yellow light emission peak at 577 nm under excitation at 389 nm,and the optimal doping concentration of Dy³⁺ions is 5%.The concentration quenching mechanism of both is electric dipole-electric dipole interaction.The energy transfer from Dy³⁺to Sm³⁺was confirmed in GZT:0.05Dy³⁺,z Sm³⁺co-doped phosphors.Under 273nm ultraviolet excitation,this series of phosphors have tunable luminous color.