Study On The Luminescence Properties Of Er³⁺ In Fluoride Nanocrystalline Of Metallic Element(Ni²⁺/Bi³⁺)

Rare earth luminescent materials have unique optical characteristics,high chemical stability,good thermal stability,and high luminescent efficiency.They have high application value in laser,display,anti-counterfeiting,biomedical imaging,solid-state luminescence and other fields,and have been widely used.The f–f or f-d transition of rare earth ions makes the trivalent lanthanide ion widely used as activators in various types of nanocrystalline.Under excitation light sources,they exhibit good luminous efficiency,color purity and sharp absorption transition.However,their absorption bands are too narrow and weak,and there is an inevitable reabsorption,which largely limits their practical applications.In order to realize the purpose of effective absorption and broadening the excitation zone,it is extremely important to explore suitable activators or sensitizers with large absorption cross section.The non-rare earth elements Ni²⁺and Bi³⁺ions have attracted much attention due to their strong and wide absorption band.Using Bi³⁺ions as an activator can generate absorption from ultraviolet to visible to infrared,and the optical properties of Bi³⁺ions are highly affected by the crystal field.In addition,Bi³⁺ion can act as a sensitizer,transferring absorbed energy to activated ions,thereby not only increasing the luminous intensity of the activated ions to a certain degree,but also adjusting the phosphor’s luminous color.This paper studies the up/down conversion light emission performance and energy transfer process of metal elements Ni²⁺and Bi³⁺ions in different rare earth fluorides.The main contents are as follows:（1）A series of Ni²⁺ion doped Na YF₄:20 mol%Yb³⁺/2 mol%Er³⁺/x mol%Ni²⁺（x=0,10,20,30,40）and Na Er F₄:x mol%Yb³⁺/y mol%Ni²⁺（x=0,5,10,15,20;y=0,5,10）nanocrystalline were prepared by hydrothermal method.Through the sample characterization of XRD,SEM,and spectroscopy,the crystal structure,the micro-morphology,the influence of upconversion luminescence properties and the energy transfer mechanism of Ni²⁺were studied.It mainly discusses whether Ni²⁺can improve the luminescence intensity of the sample in different matrices.Found that when the sample was excited at 980nm,in two different substrates,When Yb³⁺ion doping concentrations were 20mol%,the Ni²⁺ion doping enhanced the red-green peak in the Na YF₄matrix more strongly.At the same time,we found that the change of Ni²⁺ion and Yb³⁺ion doping concentration will affect the luminescence intensity of the sample.Therefore,the metal element Ni²⁺doping can improve the luminescence intensity of the sample.（2）A series of Bi³⁺ion doped Na YF₄:Yb³⁺/Er³⁺/Bi³⁺nanocrystalline were prepared by hydrothermal method.Through the sample characterization of XRD,SEM,and spectroscopy,the crystal structure,the micro-morphology,the influence of upconversion luminescence properties and the energy transfer mechanism of Bi³⁺were studied.Found that with the sample excited at 376nm,Bi³⁺ion and Yb³⁺ion formed ion pairs capable of acting together in the Na YF₄matrix.However,the sample green light emission at 523nm and 540nm was significantly reduced under the synergy of Bi³⁺ions and Yb³⁺ions,the red light emission at 656nm was significantly enhanced.Red-green ratio tuning of the sample was achieved by adjusting the ratio of Yb³⁺ions to Bi³⁺ions.It provides a reference for the coordination effect of Bi³⁺ions and Yb³⁺ions in fluoride and in the oxide matrix.