Synthesis、Characteristic And Optical Properties Of Ultraphosphate Nanomaterials With High Re³⁺ Doping Concentration

Rare earth ions doped fluorescence nanomaterials dispersion in organic solvents has a broadapplication prospect in optical amplifiers and lasers, which is expected to solve the thermalmanagement problems of the solid laser pumped under high power or high repetition frequencyfundamentally and become the new generation gain medium of high power lasers. However,nanocrystals dispersion still has two major broblems as optical gain medium, including large lossand low pump efficiency. So Carrying out the studying on refractive index matching betweennanocrystals and organic solvents, and the preparation and optical properties of rare earthstoichiometric nanocrystals, is of great research value and practical significance. In this thesis,LaF3:Nd nanocrystals dispersion in CHBr2CHBr2-DMSO is utilized to study the refractive indexmatching while dispersible LiLa1-xNdx(PO3)4micro/nanocrystals are developed to solve thecontradiction high doping concentration and long fluorescence lifetime can’t coexist.Spherical β-LaF3：Nd（10mol%）nanocrystals with small size were prepared via solvothermalprocess, and can be dispersed in mixed CHBr2CHBr2-DMSO to form transparent colloidaldispersion with high Nd3+ions concentration of1×1020cm-3. By using the differences in dispersioncapability of refractive indexes between solid and liquid, a group of wavelength with the highesttransmittance of the dispersion and refractive indexes of corresponding mixed solvents wereobtained through adjusting the volume ratio of solvents, and was fitted as the dispersion curve ofLaF3:Nd nanocrystals. The Rayleigh scattering model was also used to study the effects ofrefractive index mismatch on the dispersion’s transmittance under different wavelength, particlessize or doping concentration, which supported a new method for testing the refractive index ofnanocrystals accurately and pointed out the way to get high transmittance dispersion.On the basis of analysis and comparison of LNP crystal growth methods and the investigation ofreaction temperature, time and sovlothermal process on the optical performance ofLiLa0.4Nd0.6(PO3)4microcrystals, nevol flux-solvothermal method for prepareing dispersiable LLNPmicrocrystals with small size and regular morphology was developed. A series of LLNPmicrocrystals with excellent optical properties were synthesized, and LiLa0.4Nd0.6(PO3)4microcrystals could dispersed in CHBr2CHBr2-DMSO to form relatively transparent colloid, thefluorescence performance of which was affected by solvents weakly. According to the Judd-Ofeltmodel, a radiative lifetime of321μs, high quantum yield of32.17%and large stimulated emission cross section of4.39×10-20cm2were obtained for LiLa0.4Nd0.6(PO3)4microcrystals dispersion. Inshort, microcrystals and their dispersion possess of excellent integrated optical performance, andhas potential application in optical gain medium and glass ceramics.Based on the thermochemical theory in the propellant chemistry, urea was used as the fuel toestablish the gel-combustion method for synthesizeing LiLn(PO3)4(Ln=La、Nd、Eu) nanocrystalswith small size. By investigating the effect of heart treatment and time on the optical properties andsize,750℃-10min was selected as the best conditions, and was used to prepare a series of LLNPnanocrystals with lifetime more than120μs and LiEu(PO3)4nanocrystals with a longest lifetime of4.12ms. According to the absorption or fluorescence spectra, J-O models were utilized to calculatethe optical parameters of LNP nanocrystals dispersion in CHBr2CHBr2-DMSO and LiEu(PO3)4nanocrystals respectively. LNP nanocrystals dispersion had a radiative lifetime of321μs, amazingstimulated emission cross section of7.63×10-20cm2and high quantum yield of36.11%, while thequantum yield and stimulated emission cross section of LiEu(PO3)4nanocrystals for5D0�'7F2transition reached76.07%and4.12×10-21cm2separately, all the parameters are much higher thanthese values had been reported. Among them, LNP nanocrystals is expected to completely solve theproblem that nanocrystals dispersion can’t be pumped by LD, and LiEu(PO3)4nanocrystals have agreat potential in red phosphor, bioprobe and optical gain medium.