The Preparation Of Eu³⁺ Doped Phosphate And Molybdate Phosphors And The Studies Of Cations Effect On Their Luminescent Properties

Because white LEDs not only have long service life,but also are pollution-free,and environmentally friendly.So they are regarded as a new light source to replace the incandescent lamp and fluorescent lamp.As an important part of the white LEDs,phosphors have been extensively concerned.At present,most of the red phosphors have some defects and shortcomings.It is clear that the diversity of phosphors is conducive to the development of white LEDs.Therefore,for white LEDs,it is very important to explore novel red phosphors and find some rules of their luminescent properties.Currently,the near ultraviolet absorption of the commercial red phosphors excited by the near ultraviolet for the white LED is not strong enough.When combined with UV chip,their luminous intensities are not ideal.This shortcoming affects the fluorescence efficiency and color rendering of the white LEDs.In summary,to develop a new type rare earth doped red phosphor which can be excited by near ultraviolet has very important significance for the development and application of the white LED.Orthophosphate and molybdate are considered as the two important types of phosphors because of their excellent stability of chemical properties.On the basis of literature research and the experience of our research group,this paper makes some research on synthesis and properties of Eu³⁺ doped orthophosphates and molybdates.Using inorganic salts as raw materials,four series of red phosphor precursors have synthesized via the low-heating temperature solid-state reaction.Four series of phosphor samples?ASr?1.00-xP04:Eu³⁺x?A = Li,Na,K,x =0.02-0.10?,?LiSr?0.92-xPO₄:Eu³⁺0.08,Al³⁺x?x = 0.04-0.14?,ALa1.00-x?MoO₄?₂:Eu³⁺x?A = Li,Na,K,x = 0.02-0.10?,Li2Sr?MoO₄?:Eu³⁺x?x = 0.05-0.40?were obtained after calcining the precursors at high temperature for 3 hours in air.The samples of precursors and calcined products were characterized by XRD,SEM,UV-Vis,TG/DTG and PLE&PL.The major results and innovations of this paper are as follows:1.In both the series of?ASr?1.00-xPO:Eu³⁺x?A = Li,Na,K,x = 0.02-0.10?and the series of ALa1.00-x?MoO₄?₂:Eu³⁺x?A = Li,Na,K,x = 0.02-0.10?,monovalent cation A+ has the same effect on the fluorescence properties of the samples.That is,the smaller radius of the cation A+ has,the better fluorescence properties of samples will show.This result provides theoretical guidance for the synthesis and sifting of analpgous phosphors,such as?AB?1.00-xPO₄:Eu³⁺x?A = Li,Na,K,B = Mg,Ca,Ba?and ARe1.00-x?MoO₄?₂:Eu³⁺x?A = Li,Na,K,Re = Y,Gd,Lu?.2.The series of ALa1.00-x?MoO₄?₂:Eu³⁺x?A = Li,Na,K,x= 0.02-0.10?can be excited by both blue and near UV light.Li+ has dual enhanced effects on PA?the area of the biggest emission peak?and R?R=A2/A1,which A2 and A1 are the peak area of 5D0?7F2 to 5D0?7F1,respectively?of Eu³⁺ emission,the enhancement on PL intensity of Eu³⁺ is a major effect,and increasing R is a minor effect.This effect of Li+ is stronger than thoes of Na+,K+ and Li+ makes the emission light of samples more closer to the pure red.3.The series of ALa1.00-x?MoO₄?₂:Eu³⁺x?A = Li,Na,K,x= 0.02-0.10?phosphors are all electric-dipole dominated transition red phosphors with high value of R.4.For the series of?ASr?1.00-xPO₄:Eu³⁺x?A = Li,Na,K,x = 0.02-0.10?phosphors,Li+ and Na+ induced electric-dipole dominated transition?5D0?7F2?,and K+ induced magnetic-dipole dominated transition?5D0?7F2?.Li+ and Na+induced energy reassignment between 5D0?+7F1 and 5D0?7F2 transitions of Eu³⁺emission,which make the two samples are electric-dipole dominated transition phosphors.5.The doping of charge compensation Al³⁺ can greatly enhance the PL intensity of?LiSr?0.92-xPO₄:Eu³⁺0.08,the enhance amplitude is as high as more than 7 times.