Luminescence Properties And Applications Of Rare Earth Co-Doped Ca₂Al₂SiO₇ Phosphors Prepared By Sol-Gel Method

Rare earth doped phosphors were progressively reported for applications in lighting,fluorescence temperature measurement and anti-counterfeiting due to the advantages of environmental friendliness,long service life,high stability,low energy consumption and high luminescence efficiency.Researchers are working to explore and study how to improve the various properties of phosphors to meet the application needs of different fields.In this paper,Ca₂Al₂Si O₇（CAS）with the structure of yellow feldspar is used as the substrate by doping different rare earth ions to study how to use its special emission characteristics in the field of fluorescence temperature sensing,fluorescence anti-counterfeiting and lighting innovative applications.The specifics of the research for this paper are as follows:（1）In the first part,Tb³⁺,Eu³⁺co-doped Ca₂Al₂Si O₇ phosphors were prepared by sol-gel method.The Tb³⁺→Eu³⁺energy transfer and tunable emission based on energy transfer in this matrix were studied.To explore the effect of temperature on phosphor luminescence intensity under dual emission centers and study its temperature sensing performance based on Fluorescence intensity ratio（FIR）.Tunable luminescence was achieved when at 238 nm excitation by tuning the doping contents of Tb³⁺,Eu³⁺.Moreover,the maximum relative temperature sensitivity S_r of CAS:0.09Tb³⁺,0.07Eu³⁺phosphors reached 1.17%K^-1 at 443 K.In comparison with other Tb³⁺,Eu³⁺co-doped phosphors,a higher relative temperature sensing sensitivity is found for Tb³⁺,Eu³⁺co-doped CAS phosphors.It has the potential to be applied in the field of fluorescent temperature sensing.（2）In the second part,a series of Er³⁺single-doped and Er³⁺,Eu³⁺co-doped CAS samples were synthesized by sol-gel method in order to acquire dual-mode fluorescent anti-counterfeiting materials.The fluorescence spectroscopy and upconversion luminescence spectroscopy study revealed that CAS:Er³⁺can achieve dual-mode luminescence.Er³⁺,Eu³⁺co-doped CAS samples can attain red down-conversion luminescence and green up-conversion luminescence.By combining CAS:0.03Er³⁺,0.01Eu³⁺,CAS:0.03Er³⁺and CAS:0.01Eu³⁺phosphors,dual-mode fluorescent anti-counterfeiting can be achieved.In addition,by exploring the unique dual-mode luminescence properties of other lanthanide-doped phosphors,multi-mode luminescence anti-counterfeiting can be further realized and more color combinations can be created.（3）In the third part,the effects of different charge compensators Li⁺,Na⁺,K⁺and Mg²⁺on the crystal structures and luminescence properties of CAS:0.05Er³⁺and CAS:0.07Eu³⁺were investigated.The charge-compensating ion enhanced the luminescence intensity of CAS:0.05Er³⁺and CAS:0.07Eu³⁺had the same pattern,and the order of enhancement of luminescence intensity was I_Mg>I_K>I_Na>I_Li,and the Mg²⁺had the best effect on the enhancement of luminescence intensity.Among them,CAS:0.07 Mg²⁺,0.07Eu³⁺phosphors,with high color purity of 92.91%and good thermal stability,the phosphor can be used as a candidate material for red phosphor in white LED.