Preparetion And Luminescent Properties Of Rare Earth Doped Silicate Phosphors And Oxyfluoride Glass Ceramics

Rare earth doped phosphors and glass ceramic materials have attracted widespread attention due to their excellent optical,chemical,thermal and mechanical properties in recent years.They are widely used in various fields,such as white light emitting diodes?W-LEDs?,fluorescent display,biological imaging,optical fiber communication,temperature sensing.With the continuous development of LED chip technology,phosphors excited by near-ultraviolet LED chips have played an important role in the field of luminescent materials.However,thermal stability,color rendering index,luminous efficiency and other factors of phosphor limit their application in the field of W-LEDs.Thus,it is of great value to find phosphors,which can achieve efficient white light emission under near-ultraviolet excitation.Oxyfluoride glass ceramic is a novel composite material that combines the low phonon energy of fluoride nanocrystals with the excellent chemical and mechanical stability of glass.Therefore,the research on temperature sensing of novel oxyfluoride transparent glass ceramics owns far-reaching significance.The research content of this thesis is as follows:1.The luminescence and energy transfer of Bi³⁺/Eu³⁺co-doped Ba₂Y₂Si₄O₁₃phosphors:Bi³⁺/Eu³⁺co-doped Ba₂Y₂Si₄O₁₃3 phosphors with adjustable color and white light emission were prepared by high temperature solid phase method.Under near-ultraviolet excitation,the Ba₂Y₂Si₄O₁₃:Bi³⁺phosphor possesses two luminescence peaks at 414 and 503 nm.These two luminescence peaks come from two different cationic sites of Bi³⁺ions in Ba₂Y₂Si₄O₁₃,respectively.The energy transfer efficiency from Bi³⁺ions to Eu³⁺ions in different sites are all above 60%.Ba₂Y₂Si₄O₁₃:Bi³⁺,Eu³⁺phosphors achieve tunable luminescence and white-light emission by adjusting the excitation wavelength and doping concentration of Eu³⁺.Ba₂Y₂Si₄O₁₃:3%Bi³⁺,20%Eu³⁺phosphor exhibits excellent thermal stability characteristics.When temperature reach 473 K,the emission intensity is 82.6% of initial intensity.At room temperature,all the results show that Ba₂Y₂Si₄O₁₃:Bi³⁺,Eu³⁺ phosphor may be promising single-composition white-emitting phosphors for n-UV-based W-LEDs.2.Temperature sensing performance of Yb³⁺/Tm³⁺co-doped transparent NaY₂F₇glass ceramics:Yb³⁺/Tm³⁺oxyfluoride glass ceramics containing NaY₂F₇ nanocrystals were successfully prepared by melt quenching method and crystallization process.After the heat treatment,orthorhombic NaY₂F₇ nanocrystals were emerged in the glass matrix.Under excitation of 980 nm,all samples exhibited characteristic emission of Tm³⁺ions(¹G₄?³H₆,¹G₄?³F₄,³F_2,3?³H₆).Compared to the precursor glass?PG?,the upconversion luminescence intensity in the glass ceramics?GC?is significantly enhanced.This phenomenon indicates that Tm³⁺and Yb³⁺ions have been gethered in NaY₂F₇ nanocrystals with low phonon energy.The temperature sensing performance of the GC sample in the temperature range of 307-567 K was investigated by using the ³F₄ and ³F_2,3,3 levels of Tm³⁺ions as the thermal coupling level under 980 nm excitation.The maximum relative sensitivity of the GC sample of1.6%K^-1 is obtained.All the results show that Yb³⁺/Tm³⁺co-doped with NaY₂F₇nanocrystalline oxyfluoride glass ceramics has potential applications in optical temperature sensing.