Preparation And Characterization Of Yb And Ce Doped Nano Meter Lanthanum Borate

The 4f5d electronic configuration of rare earth atoms is not completely filled and shielded from the outside,Therefore,rare earth atoms have many electron levels,long lifetime of excited states,and many transitional channels between energy levels,in this way,a wide variety of absorbing or emitting radiation can be generated,thereby developing various luminescent materials.Rare earth luminescent materials have received more and more attention from people and become a hot spot in scientific research.Among them,rare earth luminescent materials with good optical properties can be prepared by doping rare earth elements in borate.In this experiment,lanthanum borate was synthesized by solution combustion with lanthanum nitrate and boric acid as raw materials（oxidant）,glycine,citric acid,urea,ammonium citrate as combustion agent（reductant）,ytterbium nitrate and cerium nitrate as modifiers.Lanthanum borate was modified by cerium,lanthanum borate was modified by ytterbium,lanthanum borate and cerium were co-doped with lanthanum borate.The products were analyzed by XRD,SEM,UV-VIS,PL and IR.The effects of calcining time,calcining temperature,burning agent selection on the phase composition,morphology and spectral properties of lanthanum borate powders were investigated.The experimental results are as follows:（1）Using cerium nitrate and boric acid as raw materials,glycine is a combustion agent,calcination temperature is 900°C,calcination time is 4 h,and La（NO₃）₃·nH₂O:H₃BO₃:C₂H₅NO₂=3:3:5.The lanthanum borate product particles have good dispersibility,no obvious agglomeration and sintering occurred,and the LaBO₃ particles exhibit a regular ellipsoidal shape with a particle size of about 350 nm.Can act as a good luminescent matrix material.（2）With ytterbium nitrate as modifier,the crystal structure of the matrix lanthanum borate did not change when the Yb³⁺doping amount was 3%.The unit cell parameters and unit cell volume decrease with the increase of doping amount.The crystallinity of the product is good,the morphology is regular,and the distribution is uniform.It is mainly in the shape of small ellipsoid and the particle size is about 300 nm.The ultraviolet region has a very strong absorption,and the emission band is mainly composed of a spectral band located near 421 nm.And the light absorption range of the LaBO₃ powder is also expanded.（3）LaBO₃:Ce³⁺powder was prepared by using cerium nitrate as modifier.When the Ce³⁺doping amount was 4%,the powder luminescence intensity was the highest,and the Ce³⁺doping did not shift the main peak position of the powder emission spectrum.（4）LaBO₃:Yb³⁺,Ce³⁺powders were prepared by using cerium nitrate and ytterbium nitrate as co-modifiers.The structure analysis showed that under the condition of calcination time of 4 hours,the product had good crystallinity,regular morphology and uniform distribution,and its particle size was about 300 nm.When the molar percentage of Yb³⁺and Ce³⁺doped is1.5%,the luminescence intensity of LaBO₃:Yb³⁺and Ce³⁺powders is the highest.The emission band is mainly composed of the spectral band near 421nm,and the excitation band is mainly composed of the spectral band near 255nm.