Synthesis Of Several Kinds Of Rare Earth Compound Powders And Their Microstructure And Photoluminescence Control

Rare earth with the phosphors of unique photoluminescent properties always is a hotresearch topic in materials and physics for their wide applications in color display,lighting, fiber-optic communications, anti-fake and so on. In particular, the rare earthinfrared-excited upconversion luminescent phosphors possess not only advantages ofthe photochemical stability, long fluorescence lifetime, narrow absorption andemission bands, and low biotoxicity, but also the virtues of deeper light penetration,lack of photodamage to the living organisms and no autofluorescent of biologicaltissue for using the infrared as excitation resource. The rare earth phosphors, whichcan be built as bioprobes based on these characteristics, present real and potentialapplications in bioimaging. Furthermore, many rare earth phosphors with niceparamagnetism have potential applications in magnetic resonance imaging andbioseparation. Several kinds of rare earth compound powders were synthesized withvarious approaches in this dissertation to explore the synthetic method of thesematerials, to achieve the control of their morphology, size and emission color, and todevelop new rare-earth fluorescent materials. This dissertaton studied systematicallythe effects of the synthesis on the structure, morphology and photoluminescentproperties of rare earth composites, and achieved successfully the control on them.The main contents and conclusions are listed as follows:（1） Yb₃Al₅O₁₂（YbAG） and YbAG/Yb₂O₃powders were prepared successfully bycombustion route. Red upconversion emission can be realized by Er³⁺-doping.Especially the pure red upconversion emission was realized in YbAG/Yb₂O₃powders.And the emission mechanism of pure red emission was discussed.（2） YF₃nanoparticles were synthesized via precipitation by using different fluorinesources. It is found the ammonium ions are responsible to YF₃octahedrananoparticles and the adsorption of NH₄⁺on specific crystalline face （111） was thedetermining factor to synthesize the octrahedra nanoparticles. YF₃nanobundles willbe defluorinated and oxidized to oxyfluorites which had nice upconversion property.（3） A series of LaF₃nanocrystals were synthesized with the solvothermal method inwhich the system of oleic acid, eunatrol, alcohol and water are mixed together to formthe microemulsion. Their crystalline structures and Synthetic Conditions were studied.For example, Tetragonal LiYF₄、LiYbF₄and LiLuF₄nanocrystals were prepared whenNaOH were displaced by LiOH. It is confirmed that these series of nanocrystals maybe used as host matrix materials for luminescence.（4） BaYF₅、Sr₂YF₇�'�Ba₂Er_1-xYb_xF₇rare earth fluoride nanocrystals containingalkaline earth ions were synthesized with the solvothermal method. Their crystallinestructures and controllable photoluminescence were studied. And the paramagneticproperty of Ba₂Er_1-xYb_xF₇nanocrystals were studied.