Luminescent ceramic converter and LED containing same
There is herein described a luminescent ceramic converter that comprises a flat, monolithic piece of a ceramic material containing a luminescent species wherein a concentration of the luminescent species in a peripheral region of the converter is lower than in a central region of the converter.
1. A luminescent ceramic converter comprising: a flat, monolithic piece of a ceramic material containing a luminescent species wherein a concentration of the luminescent species in a peripheral region of the converter is lower than in a central region of the converter, the ceramic material is yttrium aluminum garnet and the luminescent species is Ce 3+ , and the converter has a substantially uniform concentration of cerium and at least a portion of the cerium in the peripheral region is Ce 4+ .
2. The luminescent ceramic converter of claim 1 wherein the peripheral region has a width of less than about 100 micrometers and surrounds the central region of the converter.
3. The luminescent ceramic converter of claim 1 wherein the converter has a substantially rectangular shape.
4. A luminescent ceramic converter comprising: a flat, monolithic piece of a ceramic material containing a luminescent species wherein a concentration of the luminescent species in a peripheral region of the converter is lower than in a central region of the converter, the ceramic material is yttrium aluminum garnet and the luminescent species is Ce 3+ , and the amount of the luminescent species in the peripheral region has been reduced by evaporation.
5. A method of making a luminescent ceramic converter comprising the steps of:
forming a ceramic material containing a substantially uniform concentration of a luminescent species; and
treating said ceramic material by selectively evaporating a portion of said luminescent species to reduce the concentration of said luminescent species in a peripheral region thereof and complete said luminescent ceramic converter.
6. A light emitting device comprising:
a blue-light emitting LED; and
a luminescent ceramic converter plate overlying said blue-light emitting LED, the converter plate comprising a flat, monolithic piece of a ceramic material containing a luminescent species wherein a concentration of the luminescent species in a peripheral region of the converter is lower than in a central region of the converter, the ceramic material is yttrium aluminum garnet and the luminescent species is Ce 3+ , and wherein the converter has a substantially uniform concentration of cerium and at least a portion of the cerium in the peripheral region is Ce 4+ .
7. The light-emitting device of claim 6 wherein the peripheral region has a width of less than about 100 micrometers and surrounds the central region of the converter.
8. The light-emitting device of claim 6 wherein the converter has a substantially rectangular shape.