The Preparation And Characterization Of Rare Earth Doped Na₂Ca₃Si₂O₈ And BaZrSi₃O₉ Based Luminescent Materials

In the first part of this dissertation, we systematically introduced the research histories,recent research situations and future application prospects on inorganic luminescent phosphors for w-LEDs, long persistent luminescence phosphors, photostimulated long persistent luminescence and tunable emission color materials and mechanoluminescence. Aiming at the hotspots and confronting challenges, we have carried out massive related experiments and optimization. The main research contents and results in this dissertation are summarized as follows:（1） A series of novel red-emitting Na₂Ca₃-xSi₂O₈:xEu³⁺ phosphors were synthesized by solid state reactions.The phosphors can strongly absorb 395nm light, and show red emission with a good color purity.The excitation and emission spectra properties of Na₂Ca₃Si₂O₈:Eu³⁺were characterized.Na₂Ca₃Si₂O₈:Eu³⁺ with self-compensated and alkali metal ions charge compensated approaches (2Ca2+→Eu³⁺+M+,M=Li+,Na+,K+) have investigated,which found that the red emission of luminescent intensity can be greatly enhanced, and shows superior luminescent property to the commercial Y2O2S:Eu³⁺.The present work implies that the efficient charge compensated phosphors are promising candidates as red-emitting phosphor for w-LEDs.（2） The blue-green-emitting Na₂Ca₃Si₂O₈:Tb³⁺ phosphors were prepared successfully via a traditional high temperature solid-state reaction method. The crystal phase was checked by XRD. The dependence of photoluminescence excitation （PLE）, photoluminescence （PL） and fluorescence decay properties on Tb³⁺ doping concentration was studied in detail. The emission color can be modified from blue to green based on cross-relaxation through tuning the doping concentration of Tb³⁺ ions. The cross-relaxation from 5D3 to 5D4 state which was investigated by spectroscopic and dynamic measurements was also illustrated with an energy level scheme.It may be a good candidate for blue and green phosphor.（3） A blue-emitting long persistent phosphor was prepared successfully via a traditional high temperature solid-state reaction method. The phase structure was checked by XRD. The photoluminescene and persistent luminescence decay properties of Ce³⁺-doped samples were studied systematically. The defects acting as traps were investigated by thermoluminescence. It demonstrated that the doping Ce³⁺ ions into the Na₂Ca₃Si₂O₈ host not only largely enriched the intrinsic traps but also introduced abundant new extrinsic trap which play a determining role in the generation of persistent luminescence.（4） Undoped BaZrSi₃O₉ phosphors were synthesized by a traditional solid state reaction method.Mechanoluminescence phenomenon is a type of luminescence caused by the application of mechanical energy to solids.Thermoluminescence and mechanoluminescent properties were studied. Phase and crystal structure of the obtained materials were determined by X-ray diffraction （XRD）.Photoluminescent spectrum and mechanoluminescent measurement showed that the emission peak was about 435nm.The mechanoluminescence results show that the intensities of samples are well depended on the stress,indicating that these mechanoluninescent materials can be potentially used as sensors to detect the dynamic visualization of stress distribution of an object. The obtained results suggest that the trap and the worse symmetry of crystal structure are responsible for the mechanoluninescent intensity of BaZrSi₃O₉.