Synthesis And Luminescence Properties Of Aluminate Phosphors Co-Doped With Rare Earth Ions And Manganese(Chromium)Ions

Aluminate matrix phosphors have been a hot spot for research because of their wide source and easy synthesis.Due to their generally low quantum yields and single emission centers,they cannot meet the practical needs.Therefore,it is important to carry out research on their composite phosphor as well as multi-ion photoluminescence doping modulation to improve their luminescence properties and realize their efficient multi-color luminescence with practical applications.The introductory part of this thesis summarizes the properties of aluminate matrix as well as rare earth and transition metal ion doped phosphors,the influen tial factors and their performance control methods and related lumines cence mechanism.Meanwhile,it generalizes their applications in temperature sensors,plant cultivation LED lights,optical anti-counterfiting,and other fields.Based on the feature that the doping of rare earth and transition metal ions can provide multi-color luminescence,a series of phosphors are prepared in this thesis using CaAl₄O₇ and Sr₂MgAl₂₂O₃₆ aluminates,and with Mn⁴⁺,Cr³⁺as well as rare earth ions as doped ions.And then their synthesis conditions are optimized by high-temperature solid-state reaction method.What’s more,we conducte a research on photoluminescence properties and application of phosphors.The main work is as follows:（1）A series of CaAl₄O₇:Mn⁴⁺deep red phosphors have been synthesized,and their morphological structures and fluorescence properties have been investigated.To address the problem of low photoluminescence quantum yield of CaAl ₄O₇:Mn⁴⁺phosphors,MgAl₂O₄/CaAl₄O₇:Mn⁴⁺phosphors are prepared by introducing the coexisting phase MgAl₂O₄,whose photoluminescence quantum yield is 6.74 times higher than that of CaAl₄O₇:Mn⁴⁺;the modulation effect of the presence of the coexisting phase on the luminescence properties of the composite phosphor is systematically studied.Finally,0.5MgAl₂O₄/CaAl₄O₇:0.010Mn⁴⁺in the field of temperature sensing is discussed,and its absolute sensitivity S_a is a constant value of 5.4×10^-3 K^-1 in the temperature range of 318～418 K;the maximum value of relative sensitivity is S_r=4.15×10^-3 K^-1 when the temperature is 418 K.（2）Due to the problem of accurate quantification of composite phosphor,a dual-mode emissions Sr₂MgAl₂₂O₃₆ matrix phosphor is prepared by co-doping transition metal and rare earth ions to achieve the purpose of quantitative regulation of phosphor luminescence properties.Firstly,the luminescence mechanism of Sr ₂MgAl₂₂O₃₆:Mn⁴⁺is explored and the luminescence properties of the phosphor is analyzed,f urthermore the color purity of the sample is calculated to be 72.80%.Secondly,the measure of replacing the Al³⁺-Mn⁴⁺ion pair by the Ga³⁺-Mn⁴⁺ion pair is constructed to realize the luminescence redshift of the system,and the activation energy（E_a）was calculated to be0.60 e V by the thermal stability test.The activation energy（E_a）is calculated to be 0.60e V,which is much higher than that of other Mn⁴⁺-doped red phosphors.Finally,the Mn⁴⁺,Tm³⁺co-activated Sr₂MgAl₂₂O₃₆ substrate luminescence system is designed by optimizing the concentration of Mn⁴⁺ions.The results show that the Sr₂MgAl₂₂O₃₆:Mn⁴⁺,Tm³⁺material,and can be excited by near-UV excitation light,has both deep red emission at 664 nm and blue emission at 458 nm,which overlap with photosensitive pigments（P_R）and phytochromes（carotenoids）,demonstrating its potential application in the field of indoor plant cultivation lighting.（3）Based on the fact that double-doped ions can achieve double emission in a single phase,an anti-counterfeiting scheme is designed by using a combination of Cr³⁺and Sm³⁺.By adjusting the doping concentration of Cr³⁺,a series of Sr₂MgAl₂₂O₃₆:Sm³⁺,Cr³⁺phosphors with peaks at 597 nm（orange-red light）and 696 nm（red light）with different luminescence intensities and different R/FR ratios（R:red light,FR:far-red light）are obtained.The Sr₂MgAl₂₂O₃₆:0.05Sm³⁺,0.03 Cr³⁺phosphors have the largest standard deviation corresponding to the color coordinates（0.37,0.28）and can be applied to optical anti-counterfeiting;meanwhile,their emission spectra overlap significantly with the absorption spectra of photosensitive pi gments P_R and P_FR in the range of 620～740 nm and can be applied to LED devices for plant cultivation.