Preparation And Luminescent Properties Of Rare Earth Eu³⁺ Doped Orthophosphate And Borophosphate Red Phosphors For LEDs

At present,commercial red phosphors are mainly sulphur oxide and vanadate series,can not be matched with the near UV LED chips,and are easy to break down at high temperature.Therefore,looking for a new kind of red phosphors has became a hot spot of current research.This paper used NaBaPO₄ and KBaBP₂O₈ as matrix of phosphors,the effects of doping Si⁴⁺,Gd³⁺,Li⁺,Na⁺,Ca²⁺,Sr²⁺ ons in the orthophosphate and borophosphate on the crystal structure and spectra properties of phosphors were investigated.A series of red light-emitting phosphors NaBa_1-x PO₄:xEu³⁺? NaBa_0.98Si_xP_1-x O₄: 0.02Eu³⁺?LixNa_1-xBa_0.98Si_0.02P_0.98O₄:0.02Eu³⁺ and NaBa_0.92Si_xP_1-xO₄:0.08Eu³⁺ were synthesized by the high-temperature solid-state method under the air atmosphere.The results of XRD indicate that the best calcination temperature of NaBaPO₄ phosphors is 750 ?,its matrix belongs to hexagonal crystal system,the space group is P3 ml.Doping Si⁴⁺ have no obvious influrence on the crystal form of phosphors,but it leads to the expansion of the lattice;The results of fluorescence spectrum indicate that the luminous intensity of phosphors is the largest when the calcination temperature is 750 ?.The maximum excitation peak is located in 393 nm,the main peaks are located in 591 nm?Orange?and 616nm?red?,each peak belongs to 5D0?7F2 and 5D0?7F1 transition of Eu³⁺ respectively.The strongest emission is near 616 nm in red,indicating that Eu³⁺ ions occupy the center of non inversion symmetry in the crystal lattice.A small amount of doping Si⁴⁺ and Li⁺ have no obvious influrence on the peak shape and peak position of fluorescence spectrum of NaBaPO₄:Eu³⁺,but its luminescent intensity is significantly increased.A series of orange light-emitting phosphors Li⁺,K⁺,Ca²⁺,Sr²⁺,Gd³⁺ and Si⁴⁺ doped KBa_0.9BP₂O₈:0.1Eu³⁺ were synthesized by the high-temperature solid-state method under the air atmosphere.The results of XRD indicate that calcination temperature is 850 ? when the crystallization quality of the pure KBaBP₂O₈ phase is the largest,the matrix belongs to tetragonal crystal system,its space group is I 4 2d.A small amount of doping Gd³⁺ and Si⁴⁺ have no obvious influrence on the crystal structure of phosphors,the main phase is still tetragonal KBaBP₂O₈.The results of fluorescence spectrum indicate that the maximum excitation peak is located in 394 nm,the main peaks are located in 594 nm?Orange?and 614 nm?red?,each peak belongs to 5D0?7F2 and 5D0?7F1 transition of Eu³⁺ respectively.The strongest emission is near 594 nm in orange,indicating that Eu³⁺ ions occupy the center of inversion symmetry in the crystal lattice.Doping the appropriate amount of Ca²⁺,Sr²⁺ to replace Ba²⁺,doping the appropriate amount of Li+,Na+ replace K+ can improve the luminous intensity of phosphors;A small amount of doping Si⁴⁺and Gd³⁺ have no obvious influrence on the peak position of fluorescence spectrum of NaBaPO₄:Eu³⁺,but its luminescent intensity is significantly increased.With the increase of doping mole fraction of Si⁴⁺ and Gd³⁺,more and more Eu³⁺ ions deviate from the center of inversion symmetry location,thereby the red light emission of the material system was enhanced.