Preparation And Properties Of Eu³⁺/Eu²⁺/Dy³⁺ Doped Borophosphate

White light emitting diodes（W-LEDs）are widely studied and applied due to their long lifespan,high brightness,and environmental friendliness.The classic implementation scheme of W-LED is a combination of blue gallium nitride chips（450-460nm）and yellow fluorescent powder Y₃Al₅O₁₂:Ce³⁺(YAG:Ce³⁺)which have defects such as low color rendering index（CRI,Ra<80）and high correlation color temperature（CCT>7000K）.The solution is a near-ultraviolet chip+red,green,and blue phosphors that can be effectively excited by it.Borophosphate crystals are widely used in fluorescent powders due to their diverse crystal structure types,low synthesis temperatures,and high quantum efficiency.This article uses a high-temperature solid-state method to synthesize two new boron phosphate phosphors:Ba₃BP₃O₁₂:Eu³⁺,Eu²⁺and Sr₆BP₅O₂₀:Dy³⁺.And conduct relevant research on the crystal structure,luminescence performance,concentration quenching mechanism,etc.of these two fluorescent powders（1）Pure phase barium borophosphate phosphors were prepared using a high-temperature solid-state method,and the luminescent properties of Eu³⁺and Eu²⁺ions in barium borophosphate were studied using two different valence states of rare earth europium.The results showed that under near-ultraviolet excitation at 395 nm,the peak of the strongest emission peak of Ba₃BP₃O₁₂:Eu³⁺was around 619 nm.Its luminescent color is located in the red region at the color coordinates（0.6342,0.3476）,making it a relatively superior red fluorescent powder.We also studied the maximum emission wavelength of Ba₃BP₃O₁₂:Eu²⁺under 345 nm excitation at 509 nm.The color coordinates are（0.2444,0.4471）,located in the green area.Both types of phosphors exhibit concentration quenching as the doping concentration of Eu ions increases,which is caused by non radiative energy transfer between adjacent Eu ions.During the research process,we also found that rare earth europium doped barium borophosphate phosphors synthesized in an air atmosphere can achieve self reduction of Eu³⁺to Eu²⁺.This not only helps to reduce experimental costs,but also ensures the safety of the preparation.（2）A series of Sr_6（1-x）BP₅O₂₀:6x Dy³⁺（x=0.01-0.011）.The fluorescent powder synthesized at 1120℃has high phase purity,good crystallinity,and uniform particle size distribution.XRD and FTIR analysis showed that Dy³⁺did not alter the crystal structure of the matrix Sr₆BP₅O₂₀.The luminescence performance of the sample was studied through excitation and emission spectra.The excitation spectrum of the fluorescent powder Sr₆BP₅O₂₀:Dy³⁺at a monitoring wavelength of 577 nm showed 8Dy³⁺4f-4f transition absorption peaks,with the strongest absorption peak at 350 nm originating from the energy level transition from ⁶H_15/2to ⁶P_7/2.Under excitation of 350nm ultraviolet light,the emission spectrum exhibits strong blue emission（484 nm）and yellow emission（577nm）,respectively,from the ⁴F_9/2→⁶H^15/2and ⁴F_9/2→⁶H_13/2transitions of Dy³⁺,with an average lifetime of 0.74μs.When the doping concentration of Dy³⁺is x=0.09,a significant concentration quenching effect caused by the exchange interaction between Dy³⁺ions occurs.Through the analysis of the chromaticity coordinates of the phosphor Sr_6（1-x）BP₅O₂₀:6x Dy³⁺,it can be seen that the phosphor emits light in the blue white region under ultraviolet excitation,with its color coordinates around（0.2482,0.2162）.