Study On Preparation And Luminescence Properties Of Rare Earth Ions Doped Nano LuAG Phosphors

Energy and environment are key factors to limit the development of the society all the way.Semiconductor white light-emitting diodes?LED?is regarded as green light source in the 21th century and has drawn extensive attention because of their excellent performance,such as energy saving,environmental protection,quick response,long operation life,etc.Cerium-activated lutetium aluminum garnets?Lu3Al5O12,LuAG?phosphors possess high quantum efficiency and excellent thermal stability,which can be potentially utilized as an effective phosphor to make blue chip motivated white LED.Currently,cerium-activated LuAG phosphors encounter with complicated preparation,bad particle distribution,low luminescence and lack of red emitting.In the present work,LuAG:Ce phosphors were synthesized by microwave-assisted solution combustion method.The effect of preparation technology on the microstructure and optical prpperties of LuAG:Ce phosphors was studied.The spectral properties of Sm,Pr,Eu,Cr activated LuAG phosphors were respectively investigated.The optical properties of Sm,Pr,Eu and Cr ions respectively co-doped LuAG:Ce phosphors were also studied.The detailed research content is as follows:LuAG:Ce yellow phosphors were synthesized by microwave-assisted solutioncombustion method using Lu₂O₃,HNO₃,Al?NO₃?3·9H2O,Ce?NO₃?3·6H2O and glycine as main raw materials.Results show that the phosphors show single cubic phase and uniform distribution with grain size of 20-30nm after calcined at 950? The excitation spectrum included two bands centered at 348 nm and 445 nm,indicating the phosphors can be effectively activiated by blue light,and the emission spectrum included a broad asymmetric band within 460?650 nm centered at around 505 nm.When the molar ratio of metal ions/glycine is 1:0.5,the phosphors have less surface defects and maximum luminescence intensity.The quenching concentration of Ce³⁺ ions is 1.0 mol%and the concentration quenching was attributed to the dipole-dipole interaction.There is a red shift in the emission spectra of LuAG:Ce at higher Ce³⁺ concentration.Adding 3wt%LiF decreased the crystallization temperature to 850? and enhenced the luminescence intensity of phosphors.Adding 10 mol%?NH4?2SO4 can deagglomerate the phosphors and promote the luminescence properties but increase the crystallization temperature as the decomposition of?NH4?2SO4 consumed extra energy.Different concentration of Sm³⁺,Pr³⁺,Eu³⁺ and Cr³⁺ ions activated LuAG phosphors were respectively prepared by microwave-assisted solution combustion method.LuAG:Sm phosphors exhibited excitation bands at 406 nm,418 nm and 466 nm,and the maximum emission band appear at 618 nm.The quenching concentration of Sm³⁺ is 1.50 mol%.LuAG:Pr phosphors showed excitation bands at 451 nm,460 nm and 474 nm,and the emission bands were centred at 487 nm,564 nm and 610 nm.The quenching concentration of Pr³⁺ at 610 nm is 0.50 mol%.LuAG:Eu phosphors showed excitation bands at 382 nm,394 nm and 466 nm,and the emission bands were centred at 592 nm,610 nm and 710 nm.The quenching concentration of Eu³⁺ is 10.00 mol/%.LuAG:Cr phosphors exhibited excitation bands at 458 nm and 575 nm,and the emission bands were centred at 565 nm,677 nm and 704 nm.There is no obvious concentration quenching in LuAG:Cr phosphors.These four ions doped LuAG phosphors all exhibit excitation band in blue light area and emit light in orange and red area,indicating that all these phosphors can be effectively activated by InGaN blue LED chip and emit orange and red lights.Different concentration of Sm³⁺,Pr³⁺,Eu³⁺ and Cr³⁺ with Ce³⁺ ions co-doped LuAG phosphors were prepared by microwave-assisted solution combustion method.In the emission spectra of Sm³⁺,Pr³⁺and Cr³⁺ with Ce³⁺ co-doped LuAG phosphors,there can be observed characteristic emission bands of Sm³⁺,Pr³⁺ and Cr³⁺ at 618 nm,610 nm and 704 nm respectively,apart from the characteristic yellow emission of Ce³⁺ ions.Energy transfer between Sm³⁺,Pr³⁺,Cr³⁺ and Ce³⁺ ions mainly exists in the way of nonradiative energy migration.The energy transfers from 5d excitation state of Ce³⁺ions to 465/2 state of Sm³⁺,3P0 state of Pr³⁺ and 4T2g state of Cr³⁺.The co-doping of Sm³⁺,Pr³⁺ and Cr³⁺ with Ce³⁺ enhance the orange and red light emitting and decline the color temperature of the phosphors.When the doping concentration of Sm³⁺,Pr³⁺ and Cr³⁺ ions is 3.0 mol%,1.0 mol%and 1.0 mol%,the color temperature decrease the most from 7221.94K to 6772.77K,6837.40K and 6785.31K respectively.In the emission spectra of Eu³⁺ with Ce³⁺ co-doped LuAG phosphors,however,severe luminescence quenching of Ce³⁺ emission appears,so Eu³⁺ ions are not suitable for co-doping in LuAG:Ce phosphors.In this paper,a novel and simple microwave-assisted solution combustion method was employed to synthesize uniform ions doped LuAG nano phosphors.The luminescence was intensified by process optimization and the color temperature decreased by ions co-doping compensating the red emission.The as-prepared phosphors are promising materials to develop high-efficiency and good color-rending white LED light source.