Doping Modification And Characterization Of Submicron Lanthanum Borate Powders

Because of the structure diversity,Borate materials have very good physical and chemical properties.Such as high temperature resistance,abrasion performance,high hardness,flame retardant and good nonlinear optical properties and so on.Therefore,borate has been widely studied and applied in many fields.For example,glass,ceramics,medicine and health,lubricating oil and luminescent materials and so forth.High performance materials can be prepared by means of doping modification.Doping rare earth and transition metal elements into borate has been a hot research topic.The solution combustion method can be used to prepare powders with uniform particle size and not easy sintering with simple equipment.Compared with other processes,this method has many outstanding advantages:simple process,energy saving,high purity,low cost,fast reaction,etcetera.In this paper,submicron LaBO₃ and LaBO₃ doped with Y₂O₃,Ce?NO₃?₃·6H₂O or Cr?NO₃?₃·9H₂O were prepared by the solution combustion method,respectively.The effects of reaction conditions such as the amount of doping agent,calcination temperature and reaction time on products were discussed.The composition,structure and optical properties of the products were characteristed by XRD,FT-IR,SEM,UV-Vis DRS and PL.The main contents are as follows:?1?The submicron LaBO₃ powders and Mg₂B₂O₅ submicron rods were synthesized by La?NO₃?₃·nH₂O,Mg?NO₃?₂·6H₂O,H₃BO₃ and C₂H₅NO₂ via solution combustion method.Various characterization results showed that we could prepare a high degree of crystallinity,good dispersion of submicron LaBO₃ under the molar ratio of La?NO₃?₃·nH₂O:H₃BO₃:C₂H₅NO₂=3:3:5,and calcined at 900?for 4 h.Three orthorhombic of Mg₂B₂O₅ submicron rods can be successfully prepared under the conditions of Mg:B=1:1,the calcination temperature was 900?,the calcination time was 4 h.?2?Y³⁺modified LaBO₃ powders La_?1-x?Y_xBO₃?x=1⁷%?were synthesized by solution combustion method using La?NO₃?₃·nH₂O,H₃BO₃,C₂H₅NO₂ as raw madterials and Y₂O₃ as modifier.The best modification effect of LaBO₃ were doped with 6%Y³⁺at 850?for 4 h.The PL spectra shown that Y³⁺modified LaBO₃ had a strong emission peak near 400 nm,and the luminescence intensity was greatly improved.?3?Using La?NO₃?₃·nH₂O,H₃BO₃,C₂H₅NO₂ as raw materials and Ce?NO₃?₃·6H₂O as modifier,Ce³⁺modified LaBO₃ powders La_?1-x?Ce_xBO₃?x=1⁵%?were synthesized by solution combustion method.Experimental results showed that the best experimental conditions were 2%Ce³⁺,calcined 4h at 900?.Under these conditions,UV-Vis DRS shown that the doping of Ce³⁺can increase the absorption range of light.And in the PL spectra the strong emission peaks at 357 and 379 nm correspond to the 5d-²F_5/2 and5d-²F_7/2 transitions of Ce³⁺,respectively.?4?Cr³⁺modified LaBO₃ powders La_?1-x?Cr_xBO₃?x=1⁵%?were synthesized by solution combustion method using La?NO₃?₃·nH₂O,H₃BO₃,C₂H₅NO₂ as raw materials and Cr?NO₃?₃·9H₂O as modifier.The optimum experimental conditions are as follows:the calcination temperature T was900?,the calcination time was 4 h,and the doping amount of Cr?NO₃?₃·9H₂O was 4%.According to the UV-Vis DRS,Cr³⁺modified LaBO₃ was absorbed in the whole range of 200⁸00 nm,and the absorption intensity was higher.The fluorescence spectra showed that the emission peaks were red shifted to 355 and 383 nm.Meanwhile the luminescence intensity was enhanced obviously.