Study Of Al-based Garnet Luminescent Ceramics For Solid Lighting

Laser diode（LD）lighting without light decay phenomenon and with high power,small components is considered to be a new generation of solid lighting source,which has become a hot spot in current research.However,due to the high energy density of the laser,it is difficult for phosphors to meet the requirements of laser illumination.Ceramic has the advantages of high temperature strength and good heat resistance.It is currently the most promising fluorescent material for laser lighting.Among them,YAG garnet has an isotropic crystal structure and is an excellent ceramic matrix.Therefore,the study of aluminum-based garnet luminescence ceramics was carried out in the thesis.The ceramic precursors were prepared by molten salt method,and then luminescence ceramics were prepared by using the precursors and raw materials respectively.The effects of Ce³⁺,Gd³⁺and Cr³⁺ions on the luminescent properties of luminescence ceramics were studied.The vacuum hot-press sintering（VHS）method was used to prepare luminescence ceramics,and the effects of ceramic sintering process（temperature,time,annealing temperature,etc.）on the luminescent performance were studied.And the LD devices were fabricated with synthetic luminescence ceramics,and the luminescent properties of white light LDs were studied.1.The optimal calcination temperature for preparing YAG phosphor by the molten salt method is 1350°C,and the optimal ratio of inorganic salt to the raw material is 3:1.The phosphor is used as the precursor to obtain YAG luminescence ceramics by VHS.The optimal sintering process for luminescence ceramics is determined to be 1725°C for 6h.And annealing at 1450°C for 10h can significantly increase the luminescent intensity of the ceramics.2.The pre-sintering atmosphere and ball milling time can affect the performance of the sintered body.The phase and luminescent properties of the sintered body are significantly improved in the reducing atmosphere.The sintering activity of the powder is also significantly improved after 30 hours of ball milling.In addition,the addition of Gd³⁺,Ce³⁺and Cr³⁺ions has no effect on the phase structure of the YAG sintered body.The optimal sintering process for the luminescence ceramics obtained by VHS of the sintered body is1700°C,holding for 6 hours,and the luminescent intensity is higher than that of the ceramics sintered at 1725°C with the precursor made by molten salt method.The optimal Ce³⁺ions doping concentration of luminescence ceramics is 0.06 mol,and the emission peak is between 530-535 nm.After doping with different concentrations of Gd³⁺ions,the emission peak of the sample ranges from 534.4 nm to 545.2 nm,with a red shift of 10.8 nm.After doping with Cr³⁺ions,a weak red emission peak of the sample appears between675-720 nm,and the red emission intensity tends to increase with the increase of Cr³⁺ions doping content.3.With the increase of Ce³⁺ions concentration,the color coordinates in the chromaticity diagram measured by the packaged LD device gradually moves to the direction of warm white light,the color rendering index shows a trend of first decreasing and then increasing,and the maximum luminous efficiency reaches up to 82.1 lm/W.As the thickness of the ceramic increases,the CIE color coordinates move to the yellow area.And at the same time,the color temperature,color rendering index and luminous efficiency also decrease.After the addition of Gd³⁺and Cr³⁺ions,the light spots have red shift phenomenon,forming the warm white light.Among them,the addition of Gd³⁺ions reduces the LD color rendering index and luminous efficiency.However,the luminous efficiency decreases after the addition of Cr³⁺ions,while the color rendering index increases.