Synthesis And Luminescence Properties Of Nitride Phosphor

The development of modern science and technology always stick to the topic of energy conservation and emission reduction.As the most promising solid-state lighting source in the 21st century,white LEDs won the people’s recognition by right of many advantages,such as high light efficiency,reliability,lower power consumption,pro-environment and long use lifetime.The traditional method to out white light is utilizing a blue LED chip in conjunction with a yellow-emitting phosphor of YAG:Ce³⁺,nevertheless,the color rendering index is not high owing to lacking red color composition.Therefore,it has a great significance to develop red-emitting phosphor.In this work,the Eu²⁺-,Mn²⁺-and Eu²⁺/Mn²⁺-doped CaAlSiN₃ phosphors were synthesized in N₂ atmosphere via high temperature solid-state reaction,and their luminescence properties were investigated.The results indicate that the emission spectra of Eu²⁺-doped CaAlSiN₃ phosphors show a single broad band.The optimum concentrations of Eu²⁺-doped CaAlSiN₃ phosphors were 2.0 mol%,the concentration quenching mechanism is dipole-dipole（d-d）interaction.When Mn²⁺ ions were introduced into CaAlSiN₃:0.02Eu²⁺,the emission intensity of Eu²⁺ was enhanced,and the existence of energy transfer from Mn²⁺ to Eu²⁺ was proved.The band gap of CaAlSiN₃ host was evaluated to be～3.6 eV.Ca0.975AlSiN₃:0.02Eu²⁺,0.005Mn²⁺ has the wonderful thermal stability（T50>300℃）,and the internal quantum efficiency is 84.9%.The activation energy of sample Ca0.98AlSiN₃:0.02Eu²⁺ was calculated to be about 0.293 eV.A white LED was packaged by using Ca0.975AlSiN₃:0.02Eu²⁺,0.005Mn²⁺,and the various parameters of white LED were tested.The color rendering index of Ra = 93.2,CCT =3009 K and CIE =（0.4223,0.3748）.The remarkable performance of CaAlSiN₃:Eu²⁺,Mn²⁺ phosphor signifies the spacious application foreground in the field of illumination and display.In addition,the samples CaAlSiN₃:Tb³⁺,CaAlSiN₃:Dy³⁺ were also synthesized by high temperature solid-state reaction.Spectral characteristics,the change of activators concentration and effects of co-doped with monovalent alkali metal ions as charge compensation on luminescence intensity were studied.The results show that the phosphor CaAlSiN₃:Tb³⁺ displays green-emitting,two groups of emission peak of CaAlSiN₃:Tb³⁺are attributed to the ⁵D3 → ⁷FJ（J= 6,5,4,3,2,1）and ⁵D4 →⁷FJ（J-6,5,4,3）transition of Tb³⁺,respectively.The strongest emission is attributed to ⁵D4→⁷F5 transition.The excitation peaks at 252 nm and 296 nm are ascribed to host lattice excitation and 4f8→4f75d spin-allowed transition of Tb³⁺,severally.There is cross relaxation between ⁵D3 and ⁵D4 level,and the optimized doping concentration of Tb³⁺ is 0.04 mol.Li⁺-doped sample CaAlSiN₃:Tb³⁺ showed the most significant improvement on luminescence intensity.The emission peaks of CaAlSiN₃:Dy³⁺ phosphor located at about 484 nm,582 nm,672 nm and 760 nm are assigned to the 4F9/2 →6H15/2,4F9/2 →6H13/2,4F9/2 → 6H11/:2 and 4F9/2→6H9/2 transitions of Dy³⁺,respectively.The strongest emission is attributed to 4F9/2→6H13/2 transition.The yellow phosphor CaAlSiN₃:Dy³⁺ could be applied in low-pressure mercury vapor lamps.The quenching concentration of Dy³⁺ is determined to be about 1.0 mol%,Li⁺ ions are the best charge compensator.