Rare-earth doped fluorides and process for preparing
View Patent ↗The present invention is directed to rare-earth doped solid state solutions of alkaline earth fluorides having novel luminescence properties, and to a process for preparing them. The invention is useful as identifying markers on articles. Other uses include phosphors for plasma displays, optical frequency multipliers, optical amplifiers and the like.
1. A composition comprising a rare-earth-doped solid-state solution of alkaline earth fluorides represented by the chemical formula
RE x (Ca a Sr b Ba c ) 1-x F 2+x−2y O y
wherein RE represents a three-valent rare-earth element, 0.005≦x≦0.20, and 0≦y≦0.2, a+b+c=1, with the proviso at least two of a, b, and c are not equal to zero; the composition exhibiting a luminescence spectrum having a plurality of luminescence peaks at characteristic wavelengths, at least one pair of the luminescence peaks exhibiting an intensity ratio with respect to one another that differs by at least 5% from the corresponding intensity ratio of a corresponding reference composition.
2. The composition of claim 1 wherein one of a, b, or c=0.
3. The composition of claim 1 wherein a=0.01 to 0.99, b=0.99 to 0.01, and c=0.
4. The composition of claim 1 wherein a=0.25 to 0.75, b=0.75 to 0.25, and c=0.
5. The composition of claim 1 wherein 0.01≦x≦0.10.
6. The composition of claim 1 wherein the rare earth is Eu +3 , Er +3 , or Tb +3 .
7. The composition of claim 1 wherein a=0.25 to 0.75, b=0.75 to 0.25, and c=0, 0.01≦x≦0.10, and the rare earth is Eu +3 .
8. The composition of claim 1 wherein the rare-earth doped solid-state solution of alkaline earth fluorides is in the form of particles.
9. The composition of claim 8 wherein the particles are nano-scale.
10. The composition of claim 8 wherein the particles are micro-scale.