Rare-earth doped fluorides and process for preparing
View Patent ↗The invention is directed a composition represented by the chemical formula Eu x A 1−x F 2+x−2y O y wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; the composition exhibiting a luminescence spectrum characterized by peaks at 592±2 nm and 627±2 nm, wherein the ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% larger than the corresponding peak intensity ratio at the same wavelengths of a first corresponding reference composition with the same value of x that has not been exposed to a temperature above 100° C., and wherein said ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% smaller than the corresponding peak intensity ratio at the same wavelengths of a second corresponding reference composition with the same value of x that has been subject to heating to 900° C. for 6 hours.
1. A composition represented by the chemical formula
Eu x A 1−x F 2+x−2y O y
wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; the composition exhibiting a luminescence spectrum characterized by peaks at 592±2 nm and 627±2 nm, wherein the ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% larger than the corresponding peak intensity ratio at the same wavelengths of a first corresponding reference composition with the same value of x that has not been exposed to a temperature above 100° C., and wherein said ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% smaller than the corresponding peak intensity ratio at the same wavelengths of a second corresponding reference composition with the same value of x that has been subject to heating to 900° C. for 6 hours.
2. The composition of claim 1 wherein A is selected from Ca +2 , Ba +2 , or Sr +2 .
3. The composition of claim 2 wherein A is Ca +2 .
4. The composition of claim 2 wherein A is Sr +2 .
5. The composition of claim 1 wherein 0.01≦x≦0.10.
6. A process comprising heating in the presence of oxygen a composition represented by the chemical formula
Eu x +3 A 1−x F 2+x−2y O y
wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; initially prepared at a temperature below 100° C., to a maximum temperature in the range of 200° C. to 900° C., followed by cooling to ambient temperature; with the proviso that the duration of heating not exceed six hours at 900° C., and with the further proviso that the composition so heated has not previously been exposed to the maximum temperature.
7. The process of claim 6 wherein A is selected from Ca +2 , Ba +2 , or Sr +2 .
8. The process of claim 7 wherein A is Ca +2 .
9. The process of claim 7 wherein A is Sr +2 .
10. The process of claim 6 wherein 0.01≦x≦0.10.
11. The process of claim 6 wherein the heating is effected in a series of steps.