Property Research Of YAH Microwave Dielectric Ceramics Peprepared From YAG:Ce³⁺ Phosphor

With the rapid development of semiconductor lighting technology,the usage of YAG:Ce³⁺yellow phosphor increased year by year.In order to satisfy the luminous effciency of LED lamp,the fluorescence conversion efficiency of phosphor put forward higher request,therefore screening YAG:Ce³⁺phosphor is a necessary process in order to meet the demand of luminescence properties of LED.The rest of the YAG:Ce³⁺phosphor can not meet the requirement,but the characteristic that high purity,and particle dispersion,narrow particle size distribution and crystal shape of the phosphor makes it can be used as a good raw material of YAG microwave dielectric.YAG ceramics were prepared by solid-phase sintering using YAG:Ce³⁺phosphor as raw material.Through coating active SiO₂ film on YAG:Ce³⁺phosphor by sol-gel method to improve the sintering activity and doping CaO-B₂O₃-SiO₂,CaO-MgO-SiO₂ composite oxide powder as sintering aids to reduce sintering temperature of YAG ceramics.At last,modifying the resonant frequency temperature coefficient by doping TiO₂.The main research work and results were presented as follows:?1?The lowering of phosphor's granularity,to some extent,promoted the sintering of YAG ceramic,the densification sintering temperature lowered to 1625?C from 1650?C;the relative density increased to 94.8%from 91.7%;the dielectric constant increased to 10.2 from 9.04;the value of Q·f increased to 19447GHZ from 11115GHZ.Coating tetraethoxysilane?TEOS?significantly improved the sintering activity,reduced the sintering temperature and modified the microwave dielectric properties of YAG ceramics.when the coating amount?mass friction?was 2wt%,the sintering temperature of YAG ceramics reduced to 1575?C,the relative density achieved over 96%,the samples got the pretty excellent microwave dielectric properties:?_r=10.63,Q?f=24756 GHz,?_f=-48.56ppm/?C;?2?CaO-B₂O₃-SiO₂ and CaO-MgO-SiO₂ composite oxide aids had remarkable effect on the sintering and microwave dielectric properties of Y₃Al₅O₁₂ ceramics.Experimental results show that doping 10wt%CaO-B₂O₃-SiO₂ can realize densification sintering of YAG ceramics at 1475?C,the microwave dielectric properties are:?_r=9.02,Q?f=30416 GHz,?_f=-46.98ppm/?C.Doping 15wt%CMS composite oxide aids can implement densification sintering at 1450?C,the microwave dielectric properties are:?_r=8.67,Q?f=21421GHz,?_f=-53.8ppm/?C;?3?The?_f of the Y₃Al₅O₁₂-10wt%CaO-B₂O₃-SiO₂ ceramics was modified to near-zero by TiO₂.With 10wt%TiO₂ additional,the microwave dielectric properties are:?_r=26.98,Q?f=18097GHz,?_f=-5.6ppm/?C.