Phosphor ceramic

Abstract

The present disclosure relates to a phosphor ceramic comprising a plurality of luminescence conversion materials, wherein a luminescence conversion material serves as a matrix material for the others.

Claims

1. A light emitting device, comprising a phosphor ceramic comprising at least two light emitting materials, wherein one of the materials has a melting point which is ≥200° C. lower than that of the other light emitting materials, and this material is used as matrix material, wherein the matrix material comprises one or more of the following materials: (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2SiO.sub.5, (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Si.sub.2O.sub.7, A(Tb.sub.1-x-yEu.sub.xLn.sub.y)SiO.sub.4, Ba.sub.2(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Si.sub.4O.sub.13, AE.sub.2(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Si.sub.4O.sub.13, Sr.sub.3(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Si.sub.6O.sub.18, AE.sub.3(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Si.sub.6O.sub.18, (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2GeO.sub.5, (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Ge.sub.2O.sub.7, A(Tb.sub.1-x-yEu.sub.xLn.sub.y)GeO.sub.4, Ba.sub.2(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Ge.sub.4O.sub.13, AE.sub.2(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Ge.sub.4O.sub.13, Sr.sub.3(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Ge.sub.6O.sub.18, AE.sub.3(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2Ge.sub.6O.sub.18, (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2(Ge.sub.1-a-bZr.sub.aHf.sub.b)O.sub.5, (Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2(Ge.sub.1-a-bZr.sub.aHf.sub.b).sub.2O.sub.7, A(Tb.sub.1-x-yEu.sub.xLn.sub.y)(Ge.sub.1-a-bZr.sub.aHf.sub.b)O.sub.4, Ba.sub.2(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2(Ge.sub.1-a-bZr.sub.aHf.sub.b).sub.4O.sub.13, Sr.sub.3(Tb.sub.1-x-yEu.sub.xLn.sub.y).sub.2(Ge.sub.1-a-bZr.sub.aHf.sub.b).sub.6O.sub.18, with for each material independently: Ln=La, Gd, Lu, Y or mixtures thereof, A=Li, Na, K, Rb, Cs or mixtures thereof, AE=Sr, Ca, Ba, or mixtures thereof, x>0 and <1 and y≥0 and <1, wherein 1-x-y>0 and a, b≥0 and <0.2 and z≥0 and ≤1, and the non-matrix material comprises a material with a garnet structure.

2. The light emitting device according to claim 1, wherein the matrix material has a melting point of <1300° C.

3. The light emitting device according to claim 1, wherein the matrix material is red-emitting.

4. The light emitting device according claim 1, wherein the matrix material has a melting point which is >400° C. lower than that of the other light emitting materials.

5. The light emitting device according to claim 1, wherein one of the light emitting materials, which is not the matrix material, is green-emitting or yellow-emitting.

6. The light emitting device according to claim 1, wherein one of the light emitting materials, which is not the matrix material, is blue-emitting.

7. The light emitting device according to claim 1, wherein said phosphor ceramic comprises more than one light emitting material, which is not a matrix material, and there are one or more zones or areas within the phosphor ceramic, in which essentially only selected materials under these “non-matrix” light emitting materials are present.

8. The light emitting device according to claim 1, wherein the volume fraction of the matrix material in the phosphor ceramic (in vol.-%/vol.-% in the finished phosphor ceramic) is between ≥20% and ≤99%.

9. A method of manufacturing a light emitting device according to claim 1, comprising the steps of: a) providing starting materials comprising at least one light emitting matrix material and at least one further light emitting material in powder form; b) optionally shaping, in particular by axial and/or cold isostatic pressing and/or tape casting or slot die processes and/or thermoplastic processes; c) sintering and/or hot pressing of the starting materials into a ceramic; d) optionally recompressing the sintered ceramic by hot isostatic pressing; e) optionally reworking the sintered ceramic.

10. A system comprising a light emitting device according to claim 1, the system being used in one or more of the following applications: Office lighting systems household application systems shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and decorative lighting systems portable systems automotive applications green house lighting systems.

Description

DRAWINGS

(1) The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

(2) Further details, features and advantages of the subject matter of the disclosure can be obtained from the dependent claims and from the following description of the accompanying drawings, in which—by way of example—several embodiments of the device according to the disclosure are shown, as well as with respect to the following examples, which are to be considered as purely illustrative and not restrictive. In the drawings:

(3) FIG. 1 shows a first embodiment of the light emitting device according to the disclosure

(4) FIG. 2 shows a very schematic cross section through a first phosphor ceramic of a device according to the disclosure;

(5) FIG. 3 shows a very schematic cross section through a second phosphor ceramic of a device according to the disclosure;

(6) FIG. 4 shows a very schematic cross section through a third phosphor ceramic of a device according to the disclosure;

(7) FIG. 5 shows an emission spectrum of the ceramic according to Example I;

(8) FIG. 6 shows an emission spectrum of the ceramic according to Example II;

(9) FIG. 7 shows an emission spectrum of the ceramic according to Example III;

(10) FIG. 8 shows a XRD spectrum of the ceramic of example III as well as of the two individual substances;

(11) FIG. 9 shows an emission spectrum of the ceramic according to Example IV;

(12) FIG. 10 shows an emission spectrum of the ceramic according to Example V;

(13) FIG. 11 shows an emission spectrum of the ceramic according to Example VI; and

(14) FIG. 12 shows a XRD spectrum of the ceramic of example VI as well as of the two individual substances.

(15) Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

(16) Example embodiments will now be described more fully with reference to the accompanying drawings.

(17) FIG. 1 shows a first embodiment of the light emitting device according to the disclosure in terms of a “remote phosphor” application. However, this is not restrictive and it is obvious to a person skilled in the art that also other embodiments are contemplated. According to FIG. 1 the device 1 comprises a UVA or blue emitting semiconductor device 20, which, for example, is a gallium-nitride based LED. Alternatively, the semiconductor device 20 may be a laser or may be based on other LED technologies realizing a higher radiation power per mm.sup.2 by enabling a higher current flow.

(18) The semiconductor device 20 is disposed in a reflective housing 30, above which the ceramic phosphor 10 is formed.

(19) FIG. 2 shows a very schematic cross section through a first phosphor ceramic 10 of a device according to the disclosure. As can be seen in FIG. 1, the ceramic 10 comprises a matrix material 11 in which an additional light-emitting material 12 is dispersed in the form of small grains or particles.

(20) FIG. 3 shows an alternative light emitting ceramic, in which two zones are present, which are indicated by the dashed line. In the upper zone in the figure only a “non-matrix” light-emitting material 12 is disposed, in the lower zone a further material 13 is disposed. This phosphor ceramic is preferably produced such that at first two pre-ceramics are prepared in which in one case only the material 12 and in the other case only the material 13 is processed together with the matrix material 11. Subsequently the two ceramics are bonded together and form the final phosphor ceramic.

(21) FIG. 4 shows a very schematic cross section through a third phosphor ceramic of a device according to the disclosure. As can be seen in FIG. 3, the ceramic 10 comprises a first matrix material 11 and non-emitting second matrix material 14, wherein in both two further light emitting materials 12 and 13 are dispersed in the form of smaller grains or particles. Herein, the materials 11 and 14 are preferably made of the same basic material, wherein the material 11 is doped and the material 14 is not doped.

(22) This arrangement has the advantage that the emission of the matrix material can be confined specifically to a certain region within the phosphor ceramic and, moreover, doping material can be saved.

(23) Hereinafter the disclosure is explained by way of examples, which are to be considered purely as illustrative and not as limiting.

EXAMPLE I

(24) The ceramic according to Example I comprises 90 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 10 vol.-% Lu.sub.3Al.sub.5O.sub.12:Ce(0.65%), and was prepared as follows: Synthesis of Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8

(25) 0.7894 g (4.000 mmol) BaCO.sub.3, 2.3030 g (16.000 mmol) MoO.sub.3, 0.2217 g (3.000 mmol) Li.sub.2CO.sub.3, 0.4223 g (1.200 mmol) Eu.sub.2O.sub.3 and 0.5865 g (1.800 mmol) La.sub.2O.sub.3 were pounded in a mortar with acetone as grinding aid. The obtained powder was dried, transferred to a porcelain crucible and calcinated in air at 800° C. for 12 h. The cake thus obtained was ground and sieved through a 36-μm sieve. The melting point is approximately 960 degrees C. Synthesis of Lu.sub.3Al.sub.5O.sub.12:Ce (0.65%)

(26) 2.9651 g (7.451 mmol) Lu.sub.2O.sub.3, 0.0168 g (0.098 mmol) CeO.sub.2 and 1.2745 g (12.500 mmol) Al.sub.2O.sub.3 were pounded in a mortar with acetone as grinding aid. The obtained powder was dried, transferred to a porcelain crucible and heated at 1750° C. for 12 h under a CO atmosphere. The melting point is approximately 2040-2080° C. Manufacture of the ceramic

(27) A mixture of 90 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 10 vol.-% Lu.sub.3Al.sub.5O.sub.12:Ce (0.65%) was thoroughly ground in a mill. The crude phosphor powder thus obtained was mixed with an organic glycol binder, pressed into pellets and compacted by cold isostatic pressing at 300 MPa. The thus obtained ceramic green bodies were placed on a tungsten foil and heated at 1700° in the above described reducing atmosphere. After cooling to room temperature, the ceramics were sawed into wafers. The quantum yield is 67% and the color point is located at x=0.510 and y=0.458.

(28) FIG. 5 shows the emission spectrum of the ceramic at an excitation of 465 nm.

EXAMPLE II

(29) The ceramic according to Example II comprises 85 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 15 vol.-% Lu.sub.3Al.sub.5O.sub.12:Ce(0.65%). It was prepared analogously to the ceramic of Example I. The quantum yield is 68% and the color point is located at x=0.473 and y=0.488.

(30) FIG. 6 shows the emission spectrum of the ceramic at an excitation of 465 nm.

EXAMPLE III

(31) The ceramic according to Example III comprises 80 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 20 vol.-% Lu.sub.3Al.sub.5O.sub.12:Ce(0.65%). It was also prepared analogously to the ceramic of Example I. The quantum yield is 74% and the color point is located at x=0.455 and y=0.504.

(32) FIG. 7 shows the emission spectrum of the ceramic at an excitation of 465 nm.

(33) FIG. 8 shows (from top to bottom) the XRD spectra of the ceramic as well as the powder spectra of Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and Lu.sub.3Al.sub.5O.sub.12:Ce(0.65%). As is clearly seen, no further significant peaks appear in the ceramic spectrum, i.e. during the manufacture of the ceramic virtually no reaction has occurred between the two substances.

EXAMPLE IV

(34) The ceramic according to Example IV comprises 90 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 10 vol.-% Y.sub.3Al.sub.5O.sub.12:Ce(2.5%). It was also prepared analogously to the ceramic of Example I. The quantum efficiency is 42% and the color point is at x=0.500 and y=0.483, the melting point of Y.sub.3Al.sub.5O.sub.12:Ce is about 1940-1980° C.

(35) FIG. 9 shows the emission spectrum of the ceramic at an excitation of 465 nm.

EXAMPLE V

(36) The ceramic according to Example V includes 85% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 15% Y.sub.3Al.sub.5O.sub.12:Ce(2.5%). It was also prepared analogously to the ceramic of Example I. The quantum yield is 51% and the color point is located at x=0.483 and y=0.500.

(37) FIG. 10 shows the emission spectrum of the ceramic at an excitation of 465 nm.

EXAMPLE VI

(38) The ceramic according to Example VI comprises 80 vol.-% Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and 20 vol.-% Y.sub.3Al.sub.5O.sub.12:Ce(2.5%). It was also prepared analogously to the ceramic of Example I. The quantum yield is 69% and the color point is 0.477 and y=0.507.

(39) FIG. 11 shows the emission spectrum of the ceramic at an excitation of 465 nm.

(40) FIG. 12 shows (from top to bottom) the XRD spectra of the ceramic and the powder spectra of Li.sub.3Ba.sub.2La.sub.1.8Eu.sub.1.2(MoO.sub.4).sub.8 and Y.sub.3Al.sub.5O.sub.12:Ce(2.5%). As is clearly seen, no further significant peaks appear in the ceramic spectrum, i.e. during the manufacture of the ceramic virtually no reaction has occurred between the two substances.

(41) The individual combinations of the ingredients and the characteristics of the embodiments mentioned above are exemplary, the exchange and substitution of the teachings included in this publication with other teachings included in the cited documents are also explicitly contemplated. A person skilled in the art will recognize that variations and modifications of the embodiments described herein and other embodiments may be realized without departing from the spirit and scope of the disclosure. Accordingly, the above description is to be considered exemplary and not as limiting. The word “comprises” used in the claims does not exclude other elements or steps. The indefinite article “a” does not exclude the importance of a plural. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. The scope of the disclosure is defined in the following claims and the associated equivalents.

(42) The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.