Preparation And Optical Properties Of YAGG-based Transparent Ceramics

As a newly developed transparent optical functional material,transparent ceramics not only have optical properties comparable to single crystals and glass,but also have the unique physical and mechanical properties.Therefore,they have received extensive attention in the field of scientific research as well as industrial applications,such as laser technology field,lighting technology field,detector technology field and optical window field.Yttrium aluminum gallium garnet(Y₃Al_5-xGa_xO₁₂,YAGG)based transparent ceramic is expected to applied in LEDs,laser lighting and long afterglow illumination based on its garnet cubic crystal structure similar to YAG with excellent physical and chemical properties,as well as great optical properties.Based on these aspects,the main contents are as following:1.In this paper,YAGG:Ce-based transparent ceramics with different Al/Ga ratios were prepared via oxygen atmosphere sintering combining hot isostatic pressing.The effects of Ga concentration on the crystal structure,morphologies,energy level structure and optical properties of YAGG:Ce ceramics were intensively investigated.As Ga concentration increased,its grain size increased and a continuous blue shift of the emission from 565 to 515 nm can be achieved.It can be seen from the chromaticity color coordinates that the emitting colors of samples transfer from warm yellow region to green region.High quality green light was obtained by coupling the YAGG:Ce ceramics with commercial blue LED chips.Transparent luminescent ceramics accomplished in this work can be quite prospective for high power LEDs application.2.The recorded spectrum of Y₃Al₃Ga₂O₁₂:Ce transparent luminescent ceramic shows that blue laser light is converted to green light with a wavelength of 520 nm,and the luminous flux can reach nearly 400 lm when irradiated by a13.7 W blue laser.Moreover,with varied temperatures of 20–80^oC,the luminous flux,spectrum and color coordinates of the sample all exhibit relatively stable,which indicates that Y₃Al₃Ga₂O₁₂:Ce transparent ceramic has great thermostability.The experiment provides an experimental basis for the application of YAGG:Ce transparent ceramics in the field of laser lighting.3.A series of Y₃Al_5-xGa_xO₁₂:Ce transparent ceramics were prepared via a two-step sintering method?oxygen atmosphere sintering combining hot isostatic pressing?.Especially,we successfully prepared YGG-based transparent ceramic for the first time.YGG(Y₃Ga₅O₁₂)has a garnet crystal structure similar to YAG and YAGG,which can offer scientists a new ceramic matrix to explore luminescent materials.By doping Dy³⁺and Cr³⁺activation ions,YGG:Dy and YGG:Cr transparent ceramics were prepared respectively.It was found that three emission peaks centered at 492 nm,581 nm and 669 nm can be observed under excitation of 353 nm for YGG:Dy transparent ceramic.Its CIE color coordinate is?0.3182,0.3326?under UV irradiation,which is a promising UV-converting candidate for WLEDs.While the emission peak of YGG:Cr transparent ceramic is at about 709 nm,which can be one of the candidate materials applied in red-emitting LEDs.The experimental results demonstrate that Y₃Ga₅O₁₂:M³⁺?M=Dy,Cr?transparent ceramics are expected to be further studied as LED luminescent materials.