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WO2008139418A2 - Green emitting luminescent materials - Google Patents

Green emitting luminescent materials Download PDF

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Publication number
WO2008139418A2
WO2008139418A2 PCT/IB2008/051887 IB2008051887W WO2008139418A2 WO 2008139418 A2 WO2008139418 A2 WO 2008139418A2 IB 2008051887 W IB2008051887 W IB 2008051887W WO 2008139418 A2 WO2008139418 A2 WO 2008139418A2
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WIPO (PCT)
Prior art keywords
systems
compound
light emitting
lighting
present
Prior art date
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Ceased
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PCT/IB2008/051887
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French (fr)
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WO2008139418A3 (en
Inventor
Thomas JÜSTEL
Petra Huppertz
Henning Ohland
Detlef Uwe Wiechert
Dominik Uhlich
Helga Bettentrup
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Intellectual Property and Standards GmbH
Koninklijke Philips Electronics NV
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Publication of WO2008139418A2 publication Critical patent/WO2008139418A2/en
Publication of WO2008139418A3 publication Critical patent/WO2008139418A3/en
Anticipated expiration legal-status Critical
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Definitions

  • the present invention is directed to novel luminescent materials for light emitting devices, especially to the field of novel luminescent materials for LEDs
  • Phosphors comprising silicates, phosphates (for example, apatite) and aluminates as host materials, with transition metals or rare earth metals added as activating materials to the host materials, are widely known.
  • phosphates for example, apatite
  • aluminates as host materials, with transition metals or rare earth metals added as activating materials to the host materials.
  • transition metals or rare earth metals added as activating materials to the host materials
  • luminescent materials have been in the focus of interest and several materials have been proposed, which mostly employ Mn 2+ as emitters.
  • these luminescent materials usually have long decay times Xi io of 5 ms or more, which limit their applicability
  • LEDs may be built, which show improved lighting features, especially due to the high lumen equivalent, their fast decay, and their high conversion efficiency of many compounds of the inventive - Due to the fact that many compounds within the present invention have rather low melting point of the materials ( 1000 - 1 100 0 C), their synthesis at a moderate temperature and moreover eases their processing during device manufacturing is allowed.
  • Tb + as a line emitting activator peaking at around 545 nm, these green emitting materials exhibit a high lumen equivalent.
  • the compound has >12%, more preferred >15% and most preferred >20% absorption at 487 nm and between 330 and 380 nm and a decay time Xi io of ⁇ 3 ms. This has been found to be advantageous for many applications for which the inventive compound may be of use.
  • the term "absorption between 330 and 380 nm" includes especially that the compound has this absorption over the whole range and/or over > 95 %, preferably > 97 % and most preferred > 99 % of the range between 330 and 380 nm.
  • decay time especially means that the luminescence intensity has been decreased to 1/e of the initital intensity.
  • the compound has a decay constant ti io of ⁇ 3 ms, preferably of ⁇ 2.5 ms and most preferred of ⁇ 2 ms
  • the content of Terbium in the compound is >10 %, i.e. that the factor d is >0.1. This has been found to be advantageous for many applications for which the inventive compound may be of use.
  • d is >0.2, more preferred d is >0.5 and most preferred d is >0.8.
  • the compound has a lumen equivalent of >450 lumen/W, preferably >500 lumen/W and most preferred >530 lumen/W.
  • Me is selected out of the group comprising Rb, Cs or mixtures thereof. It has been surprisingly found that the resulting compounds have a novel structure, which makes them even more advantageous for the present invention.
  • additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiOi and the like and mixtures thereof.
  • LEDs may be built which show improved lighting features, especially due to the high lumen equivalent, their fast decay, and their high conversion efficiency of many compounds of the inventive.
  • the compound Due to the application of Tb + as a line emitting activator peaking at around 545 nm, these green emitting materials exhibit a high lumen equivalent.
  • the compound has >12%, more preferred >15% and most preferred >20% at 487 nm and between 330 and 380 nm and a decay time ti K , of ⁇ 3 ms. This has been found to be advantageous for many applications for which the inventive compound may be of use.
  • absorption between 330 and 380 nm includes especially that the compound has this absorption over the whole range and/or over > 95 %, preferably > 97 % and most preferred > 99 % of the range between 330 and 380 nm.
  • decay time especially means that the luminescence intensity has been decreased to 1/e of the initital intensity.
  • the compound has a decay constant ti io of ⁇ 3 ms, preferably of ⁇ 2.5 ms and most preferred of ⁇ 2 ms
  • the content of Terbium in the compound is >20 %, i.e. that the factor d is >0.1. This has been found to be advantageous for many applications for which the inventive compound may be of use.
  • the compound has a lumen equivalent of >450 lumen/W, preferably >500 lumen/W and most preferred >530 lumen/W.
  • the present invention furthermore relates to the use of the inventive compound(s) as a luminescent material.
  • the inventive compound(s) are used in fluorescent lamps including but not limited to fluorescent lamps for illumination and LCD backlighting purposes.
  • the inventive compound(s) are used as and/or in green pixels in emissive displays, including but not limited to cathode-ray tubes, plasma display panels, and emissive LCDs.
  • the present invention furthermore relates to a light emitting material, especially a LED, ILED and/or OLED comprising at least one compound as described above.
  • the at least one compound is provided as powder and/or as ceramic material.
  • the at least one compound is provided at least partially as a powder, it is especially preferred that the powder has a d.so of >2 ⁇ m, preferably >5 ⁇ m and ⁇ 15 ⁇ m, preferably ⁇ 10 ⁇ m. This has been shown to be advantageous for a wide range of applications within the present invention.
  • the at least one compound is at least partly provided as at least one ceramic material.
  • ceramic material in the sense of the present invention means and/or includes especially a crystalline or polycrystalline compact material or composite material with a controlled amount of pores or which is pore free.
  • polycrystalline material in the sense of the present invention means and/or includes especially a material with a volume density larger than 90 percent of the main constituent, consisting of more than 80 percent of single ciystal domains, with each domain being larger than 0.5 ⁇ m in diameter and having different crystallographic orientations.
  • the single ciystal domains may be connected by amorphous or glassy material or by additional crystalline constituents.
  • a light emitting device especially a LED, ILED and/or OLED comprising at least one ceramic material with an average diameter from > 100 ⁇ m to ⁇ 2000 ⁇ m, more preferred > 200 ⁇ m to ⁇ 1500 ⁇ m, yet more preferred > 250 ⁇ m to ⁇ 1000 ⁇ m and most preferred > 300 ⁇ m to ⁇ 750 ⁇ m.
  • the at least one ceramic material has a density of >90% and ⁇ 100% of the theoretical density. This has been shown to be advantageous for a wide range of applications within the present invention since then the luminescent properties of the at least one ceramic material may be increased.
  • the at least one ceramic material has a density of >97% and ⁇ 100% of the theoretical density, yet more preferred >98% and ⁇ 100%, even more preferred >98.5% and ⁇ 100% and most preferred >99.0% and ⁇ 100%.
  • the surface roughness RMS (disruption of the planarity of a surface; measured as the geometric mean of the difference between highest and deepest surface features) of the surface(s) of the at least one ceramic material is > 0.001 ⁇ m and ⁇ 1 ⁇ m.
  • the surface roughness of the surface(s) of the at least one ceramic material is >0.005 ⁇ m and ⁇ 0.8 ⁇ m, according to an embodiment of the present invention >0.01 ⁇ m and ⁇ 0.5 ⁇ m, according to an embodiment of the present invention >0.02 ⁇ m and ⁇ 0.2 ⁇ m. and according to an embodiment of the present invention >0.03 ⁇ m and ⁇ 0.15 ⁇ m.
  • the specific surface area of the at least one ceramic material is >10 "7 ⁇ r/g and ⁇ 0.1 i ⁇ r/g.
  • a compound and/or a light emitting device may be of use in a broad variety of systems and/or applications, amongst them one or more of the following: 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
  • Fig. 1 shows an excitation, emission, and reflection spectiiim of a compound according to a first example of the present invention.
  • Fig. 2 shows a decay curve of the compound of the first example (cf.
  • Fig. 1 shows an excitation, emission, and reflection spectiiim of a compound according to a second example of the present invention.
  • Fig.4 shows a decay curve of the compound of the first example (cf.
  • Fig. 5 shows an excitation, emission, and reflection spectiiim of a compound according to a third example of the present invention.
  • Fig. 6 shows a decay curve of the compound of the first example (cf.
  • Fig. 5 shows an excitation and emission spectiiim of a compound according to a fourth example of the present invention.
  • Fig. 8 shows a decay curve of the compound of the first example (cf.
  • Example I refers to TbiMojOi:, which was made as follows:
  • the starting materials 4.486 g (6.0 mmol) MoO 3 and 5.182 g (36.0 mmol) Tb 4 C ⁇ are thoroughly mixed in a acetone shiny in an agate mortar. After the acetone has been completely evaporated the obtained powder is filled into an alumina crucible.
  • the powder is annealed for several hours at 1000 0 C in a CO atmosphere. Afterwards, it is ground again, and annealed for 12 h at 1000 0 C in air. The resulting powder is milled on a roller bench for 1 hour until and has an average particle size of 2 - 10 ⁇ m.
  • Fig. 1 shows the excitation, emission, and reflection spectiiim
  • Fig. 2 the decay curve of TbiMojOii. It can be seen that from the spectra of Fig. 1 that this compound has an unusually strong absorption in the UV-A and blue spectral range, in particular between 330 and 380 nm and between 480 and 490 nm. Furthermore from Fig. 2 it follows that this compound has a veiy short decay time.
  • Example II refers to Tb 2 W 3 Oi 2 , which was made as follows: The starting materials 1.043 g (4.5 mmol) WO 3 and 0.561 g ( 1.5 mmol) Tb 4 ⁇ 7 are thoroughly mixed in a acetone slurry in an agate mortar. After the acetone has been completely evaporated the obtained powder is filled into an alumina caicible. Then the powder is annealed for several hours at 1000 0 C in a CO atmosphere.
  • Example III refers to LiTbMoiCX which was made similar to the compounds of Example I and II.
  • Fig. 5 shows the excitation, emission, and reflection spectram
  • Fig. 6 the decay curve of LiTbMoiCX. From the figures it can be seen that this compound also has the same advantageous features as the compound of Example I (s. also Table I). In this compound the excitation spectiiim shows lesser peaks in the region between 300 and 400 nm, which may be of use for many applications within the present invention.
  • Example IV refers to Yi ⁇ which was made similar to the compounds of Example I to III.
  • Fig. 7 shows the excitation and emission spectrum
  • Fig. 8 the decay curve of Yi 6 Tb() 4 W ⁇ ,Oi2. From the figures it can be seen that this compound also has the same advantageous features as the compound of Example I (s. also Table I).
  • the excitation spectiiim shows lesser peaks in the region between 300 and 400 nm but a rather high peak in the region of about 250 nm, which may be of use for many applications within the present invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
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  • Luminescent Compositions (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

The invention relates to improved green light emitting materials of the formula Me(La 1-a-b-c-d Y a Gd b Lu c Tb d )(Mo 1-x W x ) 2 O8, (La 1-a-b-c-d Y a Gd b Lu c Tb d ) 2 (Mo 1-x W x ) 2O9 and (La 1-a-b-c-d Y a Gd b Lu c Tb d ) 2 (Mo 1-x W x )3O12. These materials have a high lumen equivalent, a fast decay, and a high conversion efficiency which makes them useful for lighting purposes.

Description

GREEN EMITTING LUMINESCENT MATERIALS
FIELD OF THE INVENTION
The present invention is directed to novel luminescent materials for light emitting devices, especially to the field of novel luminescent materials for LEDs
BACKGROUND OF THE INVENTION
Phosphors comprising silicates, phosphates (for example, apatite) and aluminates as host materials, with transition metals or rare earth metals added as activating materials to the host materials, are widely known. As blue LEDs, in particular, have become practical in recent years, the development of white light sources utilizing such blue LEDs in combination with such phosphor materials is being energetically pursued.
Especially green emitting luminescent materials have been in the focus of interest and several materials have been proposed, which mostly employ Mn2+ as emitters. However, these luminescent materials usually have long decay times Xi io of 5 ms or more, which limit their applicability
However, there is still the continuing need for green emitting luminescent materials, which are usable within a wide range of applications.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a material, which is usable within a wide range of applications and especially allows the use in applications, in which a fast decay times is advantageous.
This object is solved by a material according to claim 1 of the present invention. Accordingly, a compound Me(Lai.a.b.c.dYaGdbLucTbd)(Mθi.NWN)2θ\ is provided, whereby Me is selected out of the group comprising Li, Na, K, Cs, Rb or mixtures thereof, a, b, c, x are independently from each other >0 and <1, d is >0 and <1 and a + b + c + d = 1.0
It should be noted that by the term ,,Me(Lai.a.h.c.dYaGdbLucTbd)(Mθi. N WO2(X" especially and/or additionally any material and/or compound is meant and/or included, which has essentially this composition. The term "essentially" means especially that > 95 %, preferably > 97 % and most preferred > 99 % wt-%. However, in some applications, trace amounts of additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiOi and the like and mixtures thereof. Such a material has shown for a wide range of applications within the present invention to have at least one of the following advantages:
Using the material as luminescent material, LEDs may be built, which show improved lighting features, especially due to the high lumen equivalent, their fast decay, and their high conversion efficiency of many compounds of the inventive - Due to the fact that many compounds within the present invention have rather low melting point of the materials ( 1000 - 1 1000C), their synthesis at a moderate temperature and moreover eases their processing during device manufacturing is allowed.
Due to the application of Tb + as a line emitting activator peaking at around 545 nm, these green emitting materials exhibit a high lumen equivalent.
According to a preferred embodiment of the present invention, the compound has >12%, more preferred >15% and most preferred >20% absorption at 487 nm and between 330 and 380 nm and a decay time Xi io of < 3 ms. This has been found to be advantageous for many applications for which the inventive compound may be of use. The term "absorption between 330 and 380 nm" includes especially that the compound has this absorption over the whole range and/or over > 95 %, preferably > 97 % and most preferred > 99 % of the range between 330 and 380 nm.
The term "decay time" especially means that the luminescence intensity has been decreased to 1/e of the initital intensity.
According to a preferred embodiment of the present invention, the compound has a decay constant ti io of <3 ms, preferably of <2.5 ms and most preferred of <2 ms
According to a preferred embodiment of the present invention, the content of Terbium in the compound is >10 %, i.e. that the factor d is >0.1. This has been found to be advantageous for many applications for which the inventive compound may be of use.
Preferably d is >0.2, more preferred d is >0.5 and most preferred d is >0.8. According to a preferred embodiment of the present invention, the compound has a lumen equivalent of >450 lumen/W, preferably >500 lumen/W and most preferred >530 lumen/W. According to a preferred embodiment of the present invention, Me is selected out of the group comprising Rb, Cs or mixtures thereof. It has been surprisingly found that the resulting compounds have a novel structure, which makes them even more advantageous for the present invention.
(Cs,Rb)(Lai.a.b.c.dYaGdbLucTbd)(Mθi.NWN)2Ov crystallises as a novel structure in the tetragonal ciystal system (space group P 4/n n c ( No. 126 )). The cell parameters are α = β = γ = 90° a = 6.5475 A c = 9.5925 A cell volume = 41 1.77 A\ whereby the structur refinement was done on a basis of an x-ray diffraction pattern taken by Cu k(/ radiation.
The present invention also relates to a compound (La1-a-b-c- jYaGdilucTbd ) 2 ( Mo 1-xW02n Og +1J whereby a, b, c, x are independently from each other >0 and <1, d is >0 and <1, y is 0 or 1 and a + b + c + d = 1.0 It should be noted that by the term ,,(Lai.a.h.c.dYaGdbLucTbd)2(Mθi.
Figure imgf000006_0001
especially and/or additionally any material and/or compound is meant and/or included, which has essentially this composition.
The term "essentially" means especially that > 95 %, preferably > 97 % and most preferred > 99 % wt-%. However, in some applications, trace amounts of additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiOi and the like and mixtures thereof.
Such a material has shown for a wide range of applications within the present invention to have at least one of the following advantages:
Using the material as luminescent material, LEDs may be built which show improved lighting features, especially due to the high lumen equivalent, their fast decay, and their high conversion efficiency of many compounds of the inventive.
Due to the fact that many compounds within the present invention have rather low melting point of the materials ( 1000 - 1 1000C), their synthesis at a moderate temperature and moreover eases their processing during device manufacturing is allowed.
Due to the application of Tb + as a line emitting activator peaking at around 545 nm, these green emitting materials exhibit a high lumen equivalent. According to a preferred embodiment of the present invention, the compound has >12%, more preferred >15% and most preferred >20% at 487 nm and between 330 and 380 nm and a decay time ti K, of < 3 ms. This has been found to be advantageous for many applications for which the inventive compound may be of use.
The term "absorption between 330 and 380 nm" includes especially that the compound has this absorption over the whole range and/or over > 95 %, preferably > 97 % and most preferred > 99 % of the range between 330 and 380 nm.
The term "decay time" especially means that the luminescence intensity has been decreased to 1/e of the initital intensity.
According to a preferred embodiment of the present invention, the compound has a decay constant ti io of <3 ms, preferably of <2.5 ms and most preferred of <2 ms According to a preferred embodiment of the present invention, the content of Terbium in the compound is >20 %, i.e. that the factor d is >0.1. This has been found to be advantageous for many applications for which the inventive compound may be of use.
Preferably d is >0.2, more preferred d is >0.5 and most preferred d is >0.8. According to a preferred embodiment of the present invention, the compound has a lumen equivalent of >450 lumen/W, preferably >500 lumen/W and most preferred >530 lumen/W.
The present invention furthermore relates to the use of the inventive compound(s) as a luminescent material. According to a preferred embodiment of the present invention, the inventive compound(s) are used in fluorescent lamps including but not limited to fluorescent lamps for illumination and LCD backlighting purposes.
According to a preferred embodiment of the present invention, the inventive compound(s) are used as and/or in green pixels in emissive displays, including but not limited to cathode-ray tubes, plasma display panels, and emissive LCDs.
The present invention furthermore relates to a light emitting material, especially a LED, ILED and/or OLED comprising at least one compound as described above.
Preferably the at least one compound is provided as powder and/or as ceramic material.
If the at least one compound is provided at least partially as a powder, it is especially preferred that the powder has a d.so of >2 μm, preferably >5 μm and < 15 μm, preferably < 10 μm. This has been shown to be advantageous for a wide range of applications within the present invention. According to a preferred embodiment of the present invention, the at least one compound is at least partly provided as at least one ceramic material.
The term "ceramic material" in the sense of the present invention means and/or includes especially a crystalline or polycrystalline compact material or composite material with a controlled amount of pores or which is pore free. The term "polycrystalline material" in the sense of the present invention means and/or includes especially a material with a volume density larger than 90 percent of the main constituent, consisting of more than 80 percent of single ciystal domains, with each domain being larger than 0.5 μm in diameter and having different crystallographic orientations. The single ciystal domains may be connected by amorphous or glassy material or by additional crystalline constituents.
According to a preferred embodiment of the present invention, a light emitting device especially a LED, ILED and/or OLED is provided comprising at least one ceramic material with an average diameter from > 100 μm to < 2000 μm, more preferred > 200 μm to < 1500 μm, yet more preferred > 250 μm to < 1000 μm and most preferred > 300 μm to < 750 μm.
According to a preferred embodiment, the at least one ceramic material has a density of >90% and < 100% of the theoretical density. This has been shown to be advantageous for a wide range of applications within the present invention since then the luminescent properties of the at least one ceramic material may be increased.
More preferably the at least one ceramic material has a density of >97% and < 100% of the theoretical density, yet more preferred >98% and < 100%, even more preferred >98.5% and < 100% and most preferred >99.0% and < 100%.
According to a preferred embodiment of the present invention, the surface roughness RMS (disruption of the planarity of a surface; measured as the geometric mean of the difference between highest and deepest surface features) of the surface(s) of the at least one ceramic material is > 0.001 μm and <1 μm. According to an embodiment of the present invention, the surface roughness of the surface(s) of the at least one ceramic material is >0.005 μm and <0.8 μm, according to an embodiment of the present invention >0.01 μm and <0.5 μm, according to an embodiment of the present invention >0.02 μm and <0.2 μm. and according to an embodiment of the present invention >0.03 μm and < 0.15 μm. According to a preferred embodiment of the present invention, the specific surface area of the at least one ceramic material is >10"7 πr/g and < 0.1 iτr/g.
A compound and/or a light emitting device according to the present invention may be of use in a broad variety of systems and/or applications, amongst them one or more of the following: 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
The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, material selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional details, features, characteristics and advantages of the object of the invention are disclosed in the subclaims, the figures and the following description of the respective figures and examples, which —in an exemplary fashion— show several embodiments and examples of inventive compounds Fig. 1 shows an excitation, emission, and reflection spectiiim of a compound according to a first example of the present invention. Fig. 2 shows a decay curve of the compound of the first example (cf.
Fig. 1 ) Fig. 3 shows an excitation, emission, and reflection spectiiim of a compound according to a second example of the present invention. Fig.4 shows a decay curve of the compound of the first example (cf.
Fig. 3)
Fig. 5 shows an excitation, emission, and reflection spectiiim of a compound according to a third example of the present invention.
Fig. 6 shows a decay curve of the compound of the first example (cf.
Fig. 5) Fig. 7 shows an excitation and emission spectiiim of a compound according to a fourth example of the present invention. Fig. 8 shows a decay curve of the compound of the first example (cf.
Fig. 7)
The invention will be further understood by the following Examples I to IV which - in a merely illustrative fashion - shows several materials of the present invention.
EXAMPLE I:
Example I refers to TbiMojOi:, which was made as follows:
The starting materials 4.486 g (6.0 mmol) MoO3 and 5.182 g (36.0 mmol) Tb4C^ are thoroughly mixed in a acetone shiny in an agate mortar. After the acetone has been completely evaporated the obtained powder is filled into an alumina crucible.
Then the powder is annealed for several hours at 10000C in a CO atmosphere. Afterwards, it is ground again, and annealed for 12 h at 10000C in air. The resulting powder is milled on a roller bench for 1 hour until and has an average particle size of 2 - 10 μm.
Fig. 1 shows the excitation, emission, and reflection spectiiim, Fig. 2 the decay curve of TbiMojOii. It can be seen that from the spectra of Fig. 1 that this compound has an unusually strong absorption in the UV-A and blue spectral range, in particular between 330 and 380 nm and between 480 and 490 nm. Furthermore from Fig. 2 it follows that this compound has a veiy short decay time.
Without being bond to any theory, the inventors believe that these surprising features of the inventive compounds at least result partly as a consequence of the rather high covalent character of the host lattice and the activator-oxygen bonds. This may then result in a partly relaxation of the spin selection rule and thus into a higher transition probability of the respective 4f-4f transitions (absorption: 7F6 - "D4 and 7F6 - D3; emission: D4 - 7Fj). The decay time and the color points x and y of this compound and the compounds of Example II and III (to be discussed further on) are given in Table I
Table I
Figure imgf000011_0001
EXAMPLE II:
Example II refers to Tb2W3Oi2, which was made as follows: The starting materials 1.043 g (4.5 mmol) WO3 and 0.561 g ( 1.5 mmol) Tb4θ7 are thoroughly mixed in a acetone slurry in an agate mortar. After the acetone has been completely evaporated the obtained powder is filled into an alumina caicible. Then the powder is annealed for several hours at 10000C in a CO atmosphere.
Afterwards, it is ground again, and annealed for 12 h at 10000C in air. The resulting powder is milled on a roller bench for 1 hour until and has an average particle size of 2 - 10 μm. Fig. 3 shows the excitation, emission, and reflection spectram, Fig. 4 the decay curve Of Tb2W3Oi2. From the figures it can be seen that this compound also has the same advantageous features as the compound of Example I (s. also Table I). EXAMPLE III:
Example III refers to LiTbMoiCX which was made similar to the compounds of Example I and II.
Fig. 5 shows the excitation, emission, and reflection spectram, Fig. 6 the decay curve of LiTbMoiCX. From the figures it can be seen that this compound also has the same advantageous features as the compound of Example I (s. also Table I). In this compound the excitation spectiiim shows lesser peaks in the region between 300 and 400 nm, which may be of use for many applications within the present invention.
EXAMPLE IV:
Example IV refers to Yi β
Figure imgf000012_0001
which was made similar to the compounds of Example I to III.
Fig. 7 shows the excitation and emission spectrum, Fig. 8 the decay curve of Yi 6 Tb() 4Wϊ,Oi2. From the figures it can be seen that this compound also has the same advantageous features as the compound of Example I (s. also Table I). In this compound the excitation spectiiim shows lesser peaks in the region between 300 and 400 nm but a rather high peak in the region of about 250 nm, which may be of use for many applications within the present invention.
The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.

Claims

CLAIMS:
1. Me( La ! -a-h.c. d YaGdbLucTbd KMo1 -N Wx )2(X whereby
Me is selected out of the group comprising Li, Na, K, Cs, Rb or mixtures thereof, a, b, c, x are independently from each other >0 and <1 , d is >0 and <1 and a + b + c + d = 1.0
2. The compound of claim 1, having >12% absorption at 487 nm and between 330 and 380 nm and a decay constant ti io of <3 ms.
3.
Figure imgf000013_0001
whereby a, b, c, x are independently from each other >0 and <1 , d is >0 and <1 , y is 0 or 1 and a + b + c + d = 1.0
4. The compound of claim 3, having >12% absorption at 487 nm and between 330 and 380 nm and a decay constant ti io of <3 ms.
5. Use of a compound according to any of the claims 1 to 4 as a luminescent material, especially in fluorescent lamps including but not limited to fluorescent lamps for illumination and LCD backlighting purposes and/or as and/or in green pixels in emissive displays, including but not limited to cathode-ray tubes, plasma display panels, and emissive LCDs
6. The light emitting device, especially a LED, an ILED and/or OLED comprising at least one compound according to any of the claims 1 to 4.
7. The light emitting device according to claim 6, whereby said compound is provided in form of a powder and/or ceramic.
8. The light emitting device of any of the claims 5 to 7 whereby the powder has a d.so of >2 μm and < 15 μm
9. The light emitting device of any of the claims 5 to 7, whereby the ceramic has >90% of the theoretical density
10. A system comprising a material according to any of the claims 1 to 4 and/or a light emitting device according to any of the claims 6 to 9 and/or making use according to Claim 5, 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
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