Preparation,Performance And Spectral Control Of Single-Phased Phosphor La₂Si₂O₇:Eu²⁺/Eu³⁺

White LED has the advantages of high luminous efficiency,long life,low power consumption,and fast response speed,it has gradually replaced incandescent and fluorescent lamps and is widely used in indoor,road and automotive lighting and other fields.With the improvement of living standards,the demand for lighting has shifted from pure energy saving and environmental protection to the pursuit of health and comfort,simulating the full spectrum of natural light design has become the highest requirement for light source design.At present,the main application of white light LED products on the market is that the yellow powder Y₃Al₅O₁₂:Ce³⁺is excited by the blue chip,but due to the lack of red and green components,the color rendering index is low(Ra<75)and the color temperature is high(>3000 K),it is difficult to meet the demand for high-quality lighting.Ultraviolet LEDs are more excellent in terms of electrical conversion efficiency,color rendering index and color purity,and have gradually become a more ideal light source for high-quality lighting.In recent years,ultraviolet light excites three primary color phosphors is a research hotspot in the development of full-spectrum white light LEDs,but there is a reabsorption effect between blue powder and red powder,which leads to a decrease in the luminous flux and efficiency of the light source.Ultraviolet light excites single-matrix white light emitting phosphors to become a more promising solution for high-quality white light LED lighting.At present,single-matrix white LED phosphors mainly emit multi-element rare earth luminescent ions in a coordinated manner,and the spectrum is mostly linear,with low absorption and luminous efficiency,and it is difficult to meet the demand for efficient lighting.In this subject,a new type of Eu²⁺/Eu³⁺activated La₂Si₂O₇ pyrosilicate phosphor was prepared based on the SiC reduction method assisted by the sol-gel method.Eu²⁺activated La₂Si₂O₇ has a broadband-like spectrum,showing a blue to yellow light-tunable spectral characteristic.In order to further improve the color rendering index,by controlling the degree of reduction,some Eu³⁺was introduced to supplement the red light,and La₂Si₂O₇:Eu²⁺/Eu³⁺phosphor was prepared,which realized the continuous adjustment of blue to red light.La₂Si₂O₇:Eu²⁺/Eu³⁺phosphor is characterized in that Eu exists in the form of mixed valence in the La₂Si₂O₇ matrix.There are two types of La³⁺sites in the La₂Si₂O₇lattice.When Eu enters the La₂Si₂O₇ lattice to replace La³⁺,there are three types of luminescence centers:Eu₁,Eu₂ and Eu³⁺.Eu1 is a broadband spectrum blue emission,Eu₂is a broadband spectrum yellow-green light emission,and Eu³⁺is a characteristic linear spectrum red light emission.The excitation spectrum of La₂Si₂O₇:Eu shows that after Eu³⁺is excited by the O_2p?Eu_4f charge transfer transition,there is an energy transfer from Eu³⁺?Eu²⁺,and there is an energy transfer process from Eu₁?Eu₂ at the same time.Based on the regulation of Eu doping concentration,when the Eu doping concentration is low(0.05%?0.5%),the main emission peak is the band-shaped emission of Eu²⁺,which is tunable from blue to green light.At high Eu doping concentration(0.5%?1%),the red light of Eu³⁺gradually increases as the main emission light,which can realize the wide color gamut adjustment of blue?red light.When the Eu doping concentration is 0.5%,La₂Si₂O₇:Eu appears as a single matrix white light emission.With a 254 nm UV chip,a white LED light source with Ra=91 and CCT=5800 K is designed.In order to further increase the luminous intensity of La₂Si₂O₇:Eu,the cation compensation method was tried.The substitution of Eu²⁺for La³⁺will cause a large number of oxygen vacancies to be generated in the crystal lattice.A certain amount of Li⁺and Na⁺were introduced into the system,and it was found that the compensation effect of Li⁺was better,and the luminous intensity was doubled.La₂Si₂O₇:Eu can be effectively excited by ultraviolet light,has good fluorescence thermal stability,can realize single-matrix white light emission,and has application prospects in the field of high-power full-spectrum white light LEDs.