Synthesis And Properties Of Color Tunable Silicate/Borate Phosphors

White light-emitting diodes?WLEDs?have been regarded as the fourth generation of lighting sources due to many superiorities such as energy conservation,environmental friendliness,high brightness and small size and so on.There are several approaches to realize white light,among those phosphor-converted WLEDs?pc-WLEDs?is the most common one due to simple fabrication procedure,tunable color,and easily-controlled process and so on.At present,the main method to achieve pc-WLEDs is combing a near ultraviolet chip with tricolor phosphors or combing a blue chip with yellow and red phosphors.The performance of obtained pc-WLEDs mainly depends on the luminescent properties of the selected phosphors,therefore,the preparation of phosphors with excellent luminescent properties,tunable emitting colors and excellent absorption in the near ultraviolet or blue region are of great significance.1.Ca₃?SiO₃?₃:Ce³⁺,Na⁺phosphors were prepared by a high temperature solid state reaction.Under excitations at 330 nm and 360 nm,two different emission bands can be observed peaking at 380 nm and⁴00 nm,respectively.Further analyses indicate that there should exist four different Ce³⁺luminescent centers.The phosphor with optimal Ce³⁺content Ca_2.82?SiO₃?₃:0.18Ce³⁺shows high quantum efficiencies up to90.1%and 79.5%for the above emission bands,respectively.Moreover,the selected phosphor exhibits good thermal stability and the emission intensity at 150°C remains 65%of that at the room temperature.2.A series of La₂Si₂O₇:Ce³⁺,Tb³⁺,Eu³⁺phosphors were synthesized by a high temperature solid state reaction.Under ultraviolet excitation,the emission color of the phosphor can be changed from green to orange-red by energy transfer of Ce³⁺?Tb³⁺?Eu³⁺.It shows that the phosphors have good thermal stability,the emission intensity of La_1.13Si₂O₇:0.05Ce³⁺,0.8Tb³⁺,0.02Eu³⁺phosphor at 150°C can still maintain 80%of that at room temperature.In addition,the phosphors also exhibit a high quantum efficiency,71.04%for Ce³⁺single-doped one,up to 95.60%for the Ce³⁺/Tb³⁺codoped phosphors,and the quantum efficiency values of La_1.93-y.93-y Si₂O₇:0.05Ce³⁺,yTb³⁺,0.02Eu³⁺phosphors remain higher than 70%.These results indicate that the phosphors have potential applications in pc-WLEDs.3.AseriesofSr₃Y₂?BO₃?₄:Ce³⁺,Tb³⁺,Eu³⁺phosphorswere synthesized by a high temperature solid state reaction.By changing the content of activator ions,phosphors with tunable colors can be obtained through energy transfer in the form Ce³⁺?Tb³⁺?Eu³⁺.The emitting color of the phosphors can be adjusted from blue to green then to yellow and eventually to red excited at 360 nm.In addition,the phosphors also exhibit good thermal stability,and the emission intensity at 150°C can still remain above 80%of that at room temperature,besides,the quantum efficiency of the green phosphor can reach 86.44%.These results indicate that Sr₃Y₂?BO₃?₄:Ce³⁺,Tb³⁺,Eu³⁺phosphors have promising application in pc-WLEDs as single-component color-tunable phosphors.