Synthesis And Properties Of Ca₂Si₅N₈:Eu²⁺ Phosphor Based On Porous Silicon Powder

With the continuous advancement and development of the society,white light-emitting diodes(WLEDs)are gradually replacing traditional lighting sources such as incandescent lamps and fluorescent lamps as a new generation of illumination sources due to their excellent luminous performance and energy saving and environmental protection advantages.At present,WLEDs on the market mainly use yellow LEDs to stimulate the synthesis of yellow phosphors.However,such white light still lacks a red light band,resulting in poor color rendering and high color temperature,which may easily cause eye discomfort.Ca2Si5N8:Eu2+phosphor is a rare red luminescent material that can be excited by blue light,and has the advantages of good stability and excellent spectral characteristics.However,the disadvantages of high melting point and strong inertness of the raw materials make the preparation of CaSi5N8:Eu2+ red phosphor with pure phase and excellent luminescent properties still a common problem in the world.Therefore,using of suitable raw materials to prepare pure phase and excellent luminescence performance of Ca2Si5N8:Eu2+phosphors has important practical significance for the application of such phosphors.In this paper,porous silicon powder(PSi)was used as the silicon source,and the liquid solution of metal calcium and europium was mixed with porous silicon powder.The Ca2SisN8:Eu2+phosphor was synthesized by solid phase sintering.The main research contents are as follows:Porous silicon powder was prepared by Ag+assisted chemical etching.It was found that with the increase of corrosion temperature,the pore size of porous silicon powder increased gradually,and the porous silicon powder with larger pores and uniform distribution was obtained under the corrosion temperature of 40?.The Ca2Si5N8:Eu2+ phosphor samples was synthesized based on porous silicon powder as a silicon source.After mixing with the liquid ammonia medium,Ca and Eu are deposited on the PSi in the form of a metal or metal ammonia complex.SEM showed that the synthesized samples of Ca2Si5N8:Eu2+phosphor had rough surface,good dispersion and uniform particle size distribution The XRD pattern showed that the samples was Ca2SisN8 matrix,and the XPS 3d high resolution spectrum of Eu showed that the samples was pure Eu2+doped.PL showed that the emission peak of the sample excited at 465 nm was at 615 nm,which was red-shifted by 19 nm and the intensity was increased by 1.92 times compared with the sample synthesized from ordinary silicon.The effect of holding time on the properties of Ca2Si5N8:Eu2+ phosphors was investigated.As the holding time increases,the sample becomes pure phase,the unit cell volume and crystallinity increase first and then decrease,and the band gap value decreases first and then increases.When the holding time is 4 h,the unit volume of the sample is the smallest and the crystallinity is good.The band gap value of the sample is the smallest and the emission peak is high.The effect of PSi corrosion temperature on the properties of Ca2Si5N8:Eu2+phosphors was investigated.As the corrosion temperature of PSi increases,the unit cell parameters of the sample slightly expand on the b-axis,shrink on the a-axis and the c-axis,and the unit cell shrinks first and then expands,and the crystallinity first increases and then decreases.When the corrosion temperature is 40?,the fluorescence emission is the strongest,the red shift position is the most significant,the emission peak is red from 596 nm to 615 nm,and the fluorescence lifetime begins to decrease when the corrosion temperature is 50?.