Phosphor in polycrystalline ceramic structure and a light-emitting element comprising same
View Patent ↗The invention relates to a phosphor in a polycrystalline ceramic structure and a light-emitting element provided with the same comprising a Light-Emitting Diode (LED) in which a composite structure of phosphor particles is embedded in a matrix, characterized in that the matrix is a ceramic composite structure comprising a polycrystalline ceramic alumina material, hereafter called luminescent ceramic matrix composite. This luminescent ceramic matrix composite can be made by the steps of converting a powder mixture of ceramic phosphor particles and alumina particles into a slurry, shaping the slurry into a compact, and applying a thermal treatment, optionally in combination with hot isostatic pressing into a polycrystalline phosphor-containing ceramic alumina composite structure. The luminescent ceramic matrix composite further allows a method of tuning the light-diffusing properties by changing at least one of the fractions of phosphor particles and second ceramic particles, the grain size of the particles of the ceramic composite structure, the difference in the refractive index of the particles of the ceramic composite structure, and the porosity in the polycrystalline phosphor-containing ceramic composite structure.
1. A phosphor in, a polycrystalline ceramic structure comprising pores within the polycrystalline ceramic structure and a phosphor of the doped YAG type, characterized in that the phosphor is embedded in a ceramic matrix comprising non-luminescent polycrystalline alumina,
wherein the ceramic matrix comprises 80 to 99.99 vol. % alumina and 0.01 to 20 vol. % phosphor,
wherein the porosity is less than or equal to 1% of the ceramic matrix,
wherein at least 90% of the pores of the ceramic matrix composite have an average pore size of less than 300 nm.
2. The phosphor in the polycrystalline ceramic structure of claim 1 , wherein the phosphor is a doped YAG having the composition (Lu 1-x-y-a-b Y x Gd y ) 3 (Al 1-z Ga z ) 5 0 12 :Ce a Pr b , with 0≦x≦1; 0≦y<1; 0≦z≦0.1; 0≦a≦0.2 and 0≦b≦0.1, and a+b>0.
3. The phosphor in the polycrystalline ceramic structure of claim 1 , wherein the ceramic matrix comprises 90 to 99.9 vol. % alumina and 0.1 to 10 vol. % phosphor.
4. The phosphor in the polycrystalline ceramic structure of claim 3 , wherein the matrix comprises 95 to 99 vol. % alumina and 1 to 5 vol. % phosphor.
5. The phosphor in the polycrystalline ceramic structure of claim 1 , wherein the average grain size of the grains comprised in the ceramic matrix is 0.3 to 50 μm.
6. The phosphor in the polycrystalline ceramic structure of claim 1 , wherein all of the pores of the ceramic matrix composite are less than 300 nm.