Design,Synthesis And Properties Of Single-component Spectrally-tuning Fluorescent Materials In Phosphates

White light-emitting diodes?w-LEDs?fabricated by UV-LED chips coated with white light-emitting single-component phosphors have become a current research hotspot due to various advantages for this assembly method.In this thesis,new matrixs are explored ande designed based on the mineral model of phosphate systems,and then the emission spectra are adjusted through the following two procedures including energy transfer process between the sensitizer and the activator and the single-doped activator technology route.Finally,the novel single-component direct white light fluorescent materials are prospected.A series of novel emission-tunable ScPO₄:Tb³⁺,Eu³⁺phosphors were prepared for the first time by a high temperature solid-state reaction.Tb³⁺,Eu³⁺were determined to occupy the ScO₈ coordination environment.Consequently,a tunable color emission from green to orange-red under UV light excitation was realized by the energy transfer process between Tb³⁺-Eu³⁺.Thereinto,the ScPO₄:0.03Tb³⁺,0.025Eu³⁺?yellow phosphors?exhibits good thermal stability,and they are packaged with commercial blue phosphor to fabricate w-LEDs,indicating its great potential in w-LED applications.A new phase Ca₈ZnLa?PO₄?₇ was constructed based on the mineral structural model of Whitlockite-type?-Ca₃?PO₄?₂.Then a novel single-component color tunable Ca₈ZnLa?PO₄?₇:Eu²⁺,Mn²⁺phosphors were prepared by the solid-state reaction method.Eu²⁺,Mn²⁺ions were doped into three different coordination environments of Ca²⁺.With varied Eu²⁺/Mn²⁺ratios,fine-tune emission under 365 nm excitation can be achieved from green to magenta,especially the warm white light by the process of efficient energy transfer?efficiency of 82.8%?between Eu²⁺and Mn²⁺.Furthermore,the obtained single-component direct white light fluorescent material was packaged on an ultraviolet chip to fabricate a w-LED.Based on the structure model of Whitlockite-type?-Ca₃?PO₄?₂,another new phase Ca₉Mg_1.5?PO₄?₇ was also constructed,and Eu²⁺doped Ca₉Mg_1.5?PO₄?₇ series materials were systhesised by the high temperature solid phase method.It was determined that Eu²⁺occupies the lattice of Ca²⁺and Mg²⁺ions in the matrix via the analysis of crystal structure and corresponding lumincent properties.There are two mainly emissions with multiple luminous centers:blue emission at 420 nm and yellow emission at 590 nm.With the increasing doping concentration of Eu²⁺,the ratio of blue/yellow emission is adjusted and a series of tunable fluorescent materials from dark blue to blue-white in a single-component were realized with the quenching mechanism of dipole-dipole interaction.A novel matrix KCaBi?PO₄?₂ was constructed based on the monazite?LaPO₄?mineral model.A novel white light emitting phosphor KCaBi?PO₄?₂:Dy³⁺for UV excitations has been synthesized by the solid state reaction technique.The results revealed that the KCaBi?PO₄?₂:Dy³⁺phosphors can exhibit two emission bands peaked at 480 nm?blue light?and 580 nm?yellow light?originating from the⁴F_9/2-⁶H_15/2,⁴F_9/2-⁶H_13/2 transitions of Dy³⁺,respectively.Consequently,the single-component white light emitting phosphors with better thermal stability have been illustrated,which is the potential candidate for w-LEDs.