Phosphors, such as new narrow-band red emitting phosphors for solid state lighting

Abstract

The invention provides, amongst others for application in a lighting unit, a phosphor having the formula M.sub.1xyzZ.sub.zA.sub.aB.sub.bC.sub.cD.sub.dE.sub.eN.sub.4nO.sub.n:ES.sub.xRE.sub.y (I), with M=selected from the group consisting of Ca, Sr, and Ba; Z=selected from the group consisting of monovalent Na, K, and Rb; A=selected from the group consisting of divalent Mg, Mn, Zn, and Cd; B=selected from the group consisting of trivalent B, Al and Ga; C=selected from the group consisting of tetravalent Si, Ge, Ti, and Hf; D=selected from the group consisting of monovalent Li, and Cu; E=selected for the group consisting of P, V, Nb, and Ta; ES=selected from the group consisting of divalent Eu, Sm and Yb; RE=selected from the group consisting of trivalent Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm; 0x0.2; 0y0.2; 0<x+y0.4; 0z<1; 0n0.5; 0a4 (such as 2a3); 0b4; 0c4; 0d4; 0e4; a+b+c+d+e=4; and 2a+3b+4c+d+5e=10yn+z.

Claims

1. A lighting unit comprising a light source, configured to generate light source light and a luminescent material, configured to convert at least part of the light source light into luminescent material light, wherein the light source comprises a light emitting diode (LED), and wherein the luminescent material comprises a phosphor having a UCr.sub.4C.sub.4 structure, or an ordering variant of the UCr.sub.4C.sub.4 aristotype, or a NaLi.sub.3SiO.sub.4 structure, or a KLi.sub.3GeO.sub.4 structure, having the formula:
M.sub.1xyzZ.sub.zA.sub.aB.sub.bC.sub.cD.sub.dE.sub.eN.sub.4nO.sub.n:ES.sub.x,RE.sub.y, wherein M is selected from the group consisting of Ca, Sr, and Ba Z is selected from the group consisting of monovalent Na, K, and Rb A is selected from the group consisting of divalent Mg, Mn, Zn, and Cd B is selected from the group consisting of trivalent boron, Al and Ga C is selected from the group consisting of tetravalent Si, Ge, Ti, and Hf D is selected from the group consisting of monovalent Li, and Cu E is selected from the group consisting of P, V, Nb, and Ta ES is selected from the group consisting of divalent Eu, Sm and Yb RE is selected from the group consisting of trivalent Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm 0x0.2; 0y0.2; 0<x+y0.4; 0z1; 0n0.5; 0a4; 0b4; 0c4; 0d4; 0e4; a+b+c+d+e=4; and 2a+3b+4c+d+5e=10yn+z.

2. The lighting unit according to claim 1, wherein z+d>0, and 2a3.

3. The lighting unit according to any one of the preceding claims, wherein M is selected from the group consisting of Ca and Sr, A is Mg, B is selected from the group consisting of Al and Ga, C is tetravalent Si, ES is divalent Eu, RE is selected from the group consisting of trivalent Ce, Pr, Sm, Gd, Tb, and Dy, 0<x0.2, y/x<0.1, and n0.1.

4. The lighting unit according to claim 1, wherein the luminescent material comprises one or more other phosphors selected from the group consisting of a divalent europium containing nitride luminescent material, a divalent europium containing oxynitride luminescent material, a trivalent cerium containing garnet and a trivalent cerium containing oxynitride, and wherein the light source is configured to generate blue light.

5. The lighting unit according to claim 1, wherein the luminescent material comprises one or more other phosphors selected from the group consisting of Ba.sub.0.95Sr.sub.0.05Mg.sub.2Ga.sub.2N.sub.4:Eu, BaMg.sub.2Ga.sub.2N.sub.4:Eu, SrMg.sub.3SiN.sub.4:Eu, SrMg.sub.2Al.sub.2N.sub.4:Eu, SrMg.sub.2Ga.sub.2N.sub.4:Eu, BaMg.sub.3SiN.sub.4:Eu, CaLiAl.sub.3N.sub.4:Eu, SrLiAl.sub.3N.sub.4:Eu, CaLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu, and SrLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu.

6. The lighting unit according to claim 1, wherein the phosphor complies with 0x0.2, y/x<0.1, M comprises at least Sr, z0.1, a0.4, 2.5b3.5, B comprises at least Al, c0.4, 0.5d1.5, D comprises at least Li, e0.4, n0.1, and wherein ES at least comprises Eu.

7. The lighting unit according to claim 1, wherein M is selected from the group consisting of Ca, Sr, and Ba Z is Na or z=0 A is Mg or a=0 B is selected from the group consisting of trivalent Al and Ga C is selected from the group consisting of tetravalent Si and Ge D is Li or d=0 e is 0 ES is Eu RE is Ce wherein x/y<0.1 or wherein y/x<0.1.

8. The lighting unit according to claim 1, wherein the phosphor is selected from the group consisting of
M.sub.1xyzZ.sub.zA.sub.3CN.sub.4nO.sub.n:ES.sub.x,RE.sub.y,
M.sub.1xyzZ.sub.zB.sub.3DN.sub.4nO.sub.n:ES.sub.x,RE.sub.y, and
M.sub.1xyzZ.sub.zA.sub.2B.sub.2N.sub.4nO.sub.n:ES.sub.x,RE.sub.y.

9. A phosphor having a UCr.sub.4C.sub.4 structure, or an ordering variant of the UCr.sub.4C4 aristotype, or a NaLi.sub.3SiO.sub.4 structure, or a KLi.sub.3GeO.sub.4 structure, having the formula:
M.sub.1xyzZ.sub.zA.sub.aB.sub.bC.sub.cD.sub.dE.sub.eN.sub.4nO.sub.n:ES.sub.x,RE.sub.y wherein, M is selected from the group consisting of Ca, Sr, and Ba Z is selected from the group consisting of monovalent Na, K, and Rb A is selected from the group consisting of divalent Mg, Mn, Zn, and Cd B is selected from the group consisting of trivalent boron, Al and Ga C is selected from the group consisting of tetravalent Si, Ge, Ti, and Hf D is selected from the group consisting of monovalent Li, and Cu E is selected from the group consisting of P, V, Nb, and Ta ES is selected from the group consisting of divalent Eu, Sm and Yb RE is selected from the group consisting of trivalent Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm, 0x0.2; 0y0.2; 0x+y0.4; 0z<1; 0n0.5; 0a4; 0b4; 0c4; 0d4; 0e4; a+b+c+d+e=4; and 2a+3b+4c+d+5e=10yn+z.

10. The phosphor according to claim 9, wherein z+d>0.

11. The phosphor according to claim 9, wherein A is Mg, B is selected from the group consisting of Al and Ga, C is tetravalent Si, ES is divalent Eu, RE is selected from the group consisting of trivalent Ce, Pr, Sm, Gd, Tb, and Dy, 2a3, 0x0.2, y/x<0.1, and n0.1.

12. The phosphor according to claim 9, wherein the phosphor is selected from the group consisting of (Sr,Ca)Mg.sub.3SiN.sub.4:Eu, (Sr,Ca)Mg.sub.2Al.sub.2N.sub.4:Eu, (Sr,Ca)LiAl.sub.3N.sub.4:Eu, (Sr,Ca)Li.sub.dMg.sub.aAl.sub.bN.sub.4:Eu, Ba.sub.0.95Sr.sub.0.05Mg.sub.2Ga.sub.2N.sub.4:Eu, BaMg.sub.2Ga.sub.2N.sub.4:Eu, SrMg.sub.3SiN.sub.4:Eu, SrMg.sub.2Al.sub.2N.sub.4:Eu, SrMg.sub.2Ga.sub.2N.sub.4:Eu, BaMg.sub.3SiN.sub.4:Eu, CaLiAl.sub.3N.sub.4:Eu, SrLiAl.sub.3N.sub.4:Eu, CaLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu, and SrLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu.

13. The phosphor according to claim 9, wherein RE comprises Ce, and wherein x/y<0.1 and n0.1.

14. The phosphor according to claim 9, wherein the phosphor comprises phosphor particles having a coating, wherein the coating comprises one or more coating selected from the group consisting of an AlPO.sub.4 coating, an Al.sub.2O.sub.3 coating and a SiO.sub.2 coating.

15. The phosphor according to claim 9, wherein the phosphor complies with 0x0.2, y/x<0.1, M comprises at least Sr, z0.1, a0.4, 2.5b3.5, B comprises at least Al, c0.4, 0.5d1.5, D comprises at least Li, e0.4, n0.1, and wherein ES at least comprises Eu.

16. The phosphor according to claim 9, wherein M is selected from the group consisting of Ca, Sr, and Ba Z is Na or z=0 A is Mg or a=0 B is selected from the group consisting of trivalent Al and Ga C is selected from the group consisting of tetravalent Si and Ge D is Li or d=0 e is 0 ES is Eu RE is Ce wherein x/y<0.1 or wherein y/x<0.1.

17. The phosphor according to claim 9, wherein the phosphor is selected from the group consisting of
M.sub.1xyzZ.sub.zA.sub.3CN.sub.4nO.sub.n:ES.sub.x,RE.sub.y,
M.sub.1xyzZ.sub.zB.sub.3DN.sub.4nO.sub.n:ES.sub.x,RE.sub.y, and
M.sub.1xyzZ.sub.zA.sub.2B.sub.2N.sub.4nO.sub.n:ES.sub.x,RE.sub.y.

18. An LCD display device comprising the lighting unit according to claim 1 configured as a backlighting unit.

19. The lighting unit according to claim 1, wherein: M is selected from the group consisting of Ca and Sr; A is Mg; B is selected from the group consisting of Al and Ga; C is tetravalent Si; ES is divalent Eu; RE comprises Ce; x/y<0.1; and n0.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

(2) FIGS. 1a-1d schematically depict some embodiments of the lighting unit; the drawings are not necessarily on scale;

(3) FIG. 2: Emission spectra of a plurality of different phosphors (displayed in one figure) (measured at 25);

(4) FIG. 3: Photoluminescence spectrum of Ca[LiAl.sub.3]N.sub.4 doped with 5% Europium is shown;

(5) FIG. 4a: Photoluminescence spectrum of Sr[LiAl.sub.3]N.sub.4 doped with 1% Europium in comparison with CaSiAlN.sub.3:Eu (dashed); also the reflectance spectra (r) are shown;

(6) FIG. 4b.: Low T emission spectra of SrLiAl.sub.3N.sub.4:Eu(1%). Excitation wavelength: 450 nm;

(7) FIG. 4c: shows a comparison of emission properties of some of the claimed phosphors with state of the art red emitting phosphor materials;

(8) FIG. 5a: Photoluminescence spectrum of CaLi.sub.0.5MgAl.sub.2.5N.sub.4 doped with 1% Europium;

(9) FIG. 5b: Photoluminescence spectrum of SrLi.sub.0.5MgAl.sub.2.5N.sub.4 doped with 1% Europium;

(10) FIG. 6 displays Emission spectra of SrMg.sub.2Al.sub.2N.sub.4:Eu with 0.1-5% (order curves from left to right: 0.1%; 0.2%; 0.5%; 1%; 2%; and 5% Eu, respectively); and

(11) FIG. 7: Photoluminescence spectrum of CaMg.sub.2Al.sub.2N.sub.4 doped with 1% Ce.

(12) The symbol I in graphs 2-4B, 5A-7 on the y-axis indicates the emission intensity in arbitrary units; the symbol R on the y-axis in graph 4A indicates the reflectivity with 1 being maximum reflectivity and 0 being entire absorption; SS in graph 4C indicates Stokes shift and FWHM indicates full width half maximum.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(13) FIG. 1a schematically depicts an embodiment of the lighting unit, indicated with reference 100, of the invention. The lighting unit comprises a light source 10, which is in this schematic drawing a LED (light emitting diode). In this embodiment, on top of the light source 10, here on the (light exit) surface 15, thus downstream of the light source 10, a luminescent material 20 is provided. This luminescent material 20 comprises phosphor as described herein, indicated with reference 40. By way of example, the lighting unit 100 further comprises, for instance for light extraction properties, a (transmissive) dome 61. This is an embodiment of a transmissive optical element 60, which is in this embodiment arranged downstream of the light source 10 and also downstream of the light conversion layer 20. The light source 10 provides light source light 11, which is at least partly converted by the light conversion layer 20, at least by phosphor 40, into luminescent material light 51. The light emanating from the lighting unit is indicated with reference 101, and contains at least this luminescent material light 51, but optionally, dependent upon the absorption of luminescent material 50 also light source light 11.

(14) FIG. 1b schematically depicts another embodiment, without dome, but with an optional coating 62. This coating 62 is a further example of a transmissive optical element 60. Note that the coating 62 may in an embodiment be one or more of a polymeric layer, a silicone layer, or an epoxy layer. Alternatively or additionally a coating of silicon dioxide and/or silicon nitride may be applied.

(15) In both schematically depicted embodiment of FIGS. 1a-1b, the luminescent material 20 is in physical contact with the light source 10, or at least its light exit surface (i.e. surface 15), such as the die of a LED. In FIG. 1c, however, the luminescent material 20 is arranged remote from the light source 10. In this embodiment, the luminescent material 20 is configured upstream of a transmissive (i.e. light transmissive) support 30, such as an exit window. The surface of the support 30, to which the light conversion layer 20 is applied, is indicated with reference 65. Note that the luminescent material 20 may also be arranged downstream of the support 30, or at both sides of the support luminescent material 20 may be applied. The distance between the luminescent material 20 and the light source (especially its light exit surface 15) is indicated with reference dl, and may be in the range of 0.1 mm-10 cm. Note that in the configuration of FIG. 1c, in principle also more than one light source 10 may be applied.

(16) FIG. 1d is schematically the same as FIG. 1c, but now with a plurality of light sources 10.

(17) Optionally, the luminescent material is shaped into a self-supporting layer, such as a ceramic material. In such instance, the transmissive optical element 60 may not be necessary, but may nevertheless be present.

EXPERIMENTAL

(18) As indicated above, synthesis of the claimed materials can be carried out by a variety of processing methods. It has been found by the inventors that keeping firing temperatures low (below 1200 C.) improves phase purity and luminescence properties of the claimed phases. It turned out that reactive precursors like intermetallic phases obtained by melting of the constituent M, Z, A, B, C, D and E metals, alkaline earth amides, or silicon diimide are especially suitable. The addition of flux materials like fluorides or chlorides is also improving phase formation. Suitable synthesis methods comprise high pressure nitridation, processing in alkaline metal melts, ammonothermal synthesis and standard mix and fire approaches.

(19) Synthesis of BaMg.sub.2Ga.sub.2N.sub.4:Eu

(20) 5 g BaH.sub.2 powder made by hydrogenation of Ba and 1.744 g Mg powder are mixed and fired for 4 h under N.sub.2/H.sub.2 (95/5) at 800 C. 4 g of the obtained BaMg.sub.2N.sub.2 is mixed with 3.131 g GaN powder and 0.039 g EuF.sub.3 and fired at 850 C. for 4 hrs. under flowing N.sub.2 atmosphere followed by pressure sintering at 1000 C., 500 bar N.sub.2 pressure for 4 hrs. To remove remaining BaGa.sub.4 impurity phase, the pressure treatment may be repeated after milling of the sample.

(21) Alternative Synthesis of BaMg.sub.2Ga.sub.2N.sub.4:Eu

(22) Starting from the elements Ba, Mg, Ga in a molar ratio of 0.24:0.26:1 with NaN.sub.3 (1.3 mol %) and EuF.sub.3 (0.004 mol %) in a Na-flux, the mixture is fired in weld shut metal ampoules for 48 h at 760 C. and then slowly cooled down within 165 h to 200 C. The inhomogeneous product is purified by sublimation of Na after reaction.

(23) Synthesis of SrMg.sub.2Al.sub.2N.sub.4:Eu

(24) A mixture of SrAl.sub.2(NH.sub.2).sub.8, LiAlH.sub.4, Mg, and LiN.sub.3 in a molar ratio 1:2:1:2.6 with Eu(NH.sub.2).sub.2 (0.03 mol %) in Li flux is fired in weld shut tantalum ampoules for 24 h at 900 C. SrMg.sub.2Al.sub.2N.sub.4:Eu is obtained.

(25) Synthesis of MMg.sub.3SiN.sub.4:Eu (M=Ca,Sr,Ba)

(26) Starting from M, Eu, silicon diimide Si(NH).sub.2 and Mg in a molar ratio of 1:1:3, the mixture is heated in an open tungsten crucible to 900 C. in 1.5 h under nitrogen atmosphere, kept for 8 h at this temperature and subsequently quenched to room temperature by switching off the furnace. A homogeneous powder containing (M,Eu)Mg.sub.3SiN.sub.4 is obtained.

(27) Alternative Synthesis of MMg.sub.3SiN.sub.4:Eu (M=Ca, Sr, Ba)

(28) A mixture of MF.sub.2, EuF.sub.3, Mg.sub.3N.sub.2, Si(NH).sub.2 and LiN.sub.3 in a molar ratio 0.99:0.01:1:1:2 in Li flux is fired in weld shut tantalum ampoules for 24 h at 900 C. MMg.sub.3SiN.sub.4:Eu is obtained. Fluoride byproducts can be removed by sublimation under vacuum.

(29) Excitation and emission were measured with a custom-made spectrofluorimeter. The herein described phosphors are well excitable in the blue spectral range which makes them especially useful for application in phosphor converted LEDs with blue pump emission. Most of the systems have surprisingly an excitation maximum at or close to 450 nm.

(30) Emission spectra of some systems are depicted in FIG. 2. On the y-axis, the normalized intensities are displayed; on the x-axis the wavelength in nm. The emission spectra of Ba.sub.0.95Sr.sub.0.05Mg.sub.2Ga.sub.2N.sub.4; Eu (1), BaMg.sub.2Ga.sub.2N.sub.4:Eu (2), SrMg.sub.3SiN.sub.4:Eu (3), SrMg.sub.2Al.sub.2N.sub.4:Eu (4), and BaMg.sub.3SiN.sub.4:Eu (5) are displayed; the latter two are nearly on top of each other. Further, also the luminescence of another sample that was made, Ca0.2Sr0.8Mg3SiN4:Eu (2%), was measured. The luminescence thereof is not displayed in FIG. 2, but is with respect to its spectral position comparable to the luminescence of Ba0.95Sr0.05Mg2Ga2N4:Eu(2%), but substantially narrower (FWHM), see in below table 4.

(31) TABLE-US-00004 Composition Ba0.95Sr0.05Mg2Ga2N4: Eu(2%) Ca0.2Sr0.8Mg3SiN4: Eu(2%) Structure type UCr4C4 NaLi3SiO4 CIE x 0.6326 0.6547 CIE y 0.3669 0.345 LE (lm/W) 222 204.1 peak emission (nm) 625 626 FWHM (nm) 84 69

(32) Hence, such (Ca,Sr)Mg.sub.3SiN.sub.4, especially with Ca/Sr in the range of 0.1-0.4, are also interesting phosphors because of the spectral position and shape of the emission (luminescence).

(33) Further, also a Ce-doped compound, CaMg.sub.3SiN.sub.4:Ce(1%), crystallizing in the NaLi.sub.3SiO.sub.4 structure type, was measured, which has a yellow luminescence with an emission band maximum at about 585 nm and a spectral half width, FWHM, of about 90 nm.

(34) A number of other systems were made as well, but the not all emission spectra are displayed herein.

(35) The crystal data for Ba.sub.0.95Sr.sub.0.05Ga.sub.2Mg.sub.2N.sub.4 were estimated to be:

(36) TABLE-US-00005 Space group I4/m (No. 87) a 8.3883(12) b 8.3883(12) c 3.4393(7) 90.00 90.00 90.00 Cell volume 242.22(7) Z 2 density 2.617 g/cm.sup.3

(37) Also of other systems the crystal date were estimated, and appeared to be in conformance with the indicated (two) crystal structures.

(38) Synthesis of Ca.sub.1xLiAl.sub.3N.sub.4:Eu.sub.x

(39) Stoichiometric mixtures of CaH.sub.2, Li.sub.3N, Al, and 1 or 5 mol % EuF.sub.3 as dopant were mixed in a mortar under a protective nitrogen atmosphere. The powders were fired at 1250 C. under a nitrogen atmosphere for at least 5 hours. The photoluminescence spectrum of the phosphor excited at 444 nm reveals an emission peak at about 660 nm with a full width at half maximum (FWHM) of approximately 67 nm as visible in FIG. 3 (5% Eu sample).

(40) The lattice constants of the phosphor Ca[LiAl.sub.3]N.sub.4 obtained from X-ray diffraction measurements of a single-crystal are as follows: Crystal system: Tetragonal Space group: I4.sub.1/a a (): 11.1600 c (): 12.8650 Volume of cell (10.sup.6 pm.sup.3): 1602.28
SrLiAl.sub.3N.sub.4:Eu(1%)

(41) The phosphor is synthesized by using a conventional solid-state reaction in nitrogen atmosphere. The mixture of the starting compounds SrH.sub.2, Li.sub.3N, Al, and EuF.sub.3 is fired at 1250 C. for at least 5 hours. The calculated doping level of Europium is 1 mol %. The photoluminescence spectrum excited at 444 nm shows a peak emission at about 656 nm and a FWHM of approximately 49 nm, as shown in FIG. 4a. Low temperature emission measurements (FIG. 4b) show that the zero phonon line is located at 633 nm (15798 cm.sup.1) and the observed Stokes shift is 1014 cm.sup.1. FIG. 4b shows low T emission spectra of SrLiAl.sub.3N.sub.4:Eu(1%) at an excitation wavelength of 450 nm. FIG. 4c shows a comparison of emission properties of claimed phosphors with state of the art red emitting phosphor materials. On the x-axis, the emission band width (FWHM; full width half maximum) in cm.sup.1 is displayed, and on the y-axis the Stokes shift in cm.sup.1. Calculated values are in the high T approximation (see Henderson, Imbusch: Optical Spectroscopy of Inorganic Solids, Clarendon Press, 1989) given by FWHM=sqr(81n2)*sqr(2kT)*sqr(SS/2), with SS2S*h/2*.

(42) The lattice constants obtained from a Rietveld refinement are as follows: Crystal system: Triclinic Space group: P-1 a (): 10.3303 b (): 7.474 c (): 5.8713 A 100.56 B 110.50 90.38 Volume of cell (10.sup.6 pm.sup.3): 416.2
CaLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu(5%)

(43) Stoichiometric mixtures of Ca, AlF.sub.3, Mg.sub.3N.sub.2 and 5 mol % EuF.sub.3 were put in arc welded tantalum ampoules together with LiN.sub.3 and a surplus of Li metal as fluxing agent. The setup is fired at 1000 C. for at least 24 hours in inert gas atmosphere. Driving force of the reaction is the formation of the very stable LiF by metathesis. The photoluminescence spectrum of the phosphor excited at 460 nm reveals an emission peak at about 706 nm with a full width at half maximum (FWHM) of approximately 72 nm.

(44) The lattice constants of the phosphor CaLi.sub.0.5MgAl.sub.2.5N.sub.4 obtained from X-ray diffraction measurements of a single-crystal are as follows: Crystal system: Tetragonal Space group: I4/m a (): 7.9921 c (): 3.2621 Volume of cell (10.sup.6 pm.sup.3): 208.36
Rietveld refinement of bulk powder samples confirmed the lattice parameters as well as the composition: Crystal system: Tetragonal Space group: I4/m a (): 8.00392 c (): 3.26027 Volume of cell (10.sup.6 pm.sup.3): 208.8618

(45) Also a 1% Eu sample was made. The emission spectrum thereof is shown in FIG. 5a.

(46) SrLi.sub.0.5MgAl.sub.2.5N.sub.4:Eu(5%)

(47) The compound is synthesized by using a solid-sate metathesis reaction in nitrogen atmosphere. Driving force of the reaction is the formation of the very stable LiF. Stoichiometric mixtures of Sr, AlF.sub.3, Mg.sub.3N.sub.2 and 5 mol % EuF.sub.3 were put in arc welded tantalum ampoules together with LiN.sub.3 and a surplus of Li metal as fluxing agent. The setup is fired at 1000 C. for at least 24 hours in protective gas atmosphere. The photoluminescence spectrum of the phosphor excited at 450 nm reveals an emission peak at about 704 nm with a full width at half maximum (FWHM) of approximately 86 nm.

(48) The lattice constants of the phosphor SrLi.sub.0.5MgAl.sub.2.5N.sub.4 obtained from X-ray diffraction measurements of a single-crystal are as follows: Crystal system: Tetragonal Space group: I4/m a (): 8.0917 c (): 3.3166 Volume of cell (10.sup.6 pm.sup.3): 217.16

(49) Also a 1% Eu sample was made. The emission spectrum thereof is shown in FIG. 5b.

(50) Europium Concentration

(51) SrMg.sub.2Al.sub.2N.sub.4:Eu and BaMg.sub.2Al.sub.2N.sub.4:Eu were made as described above, with Europium concentrations varying from 0.1-5% and 0.1-1% respectively. A (red) shift of 100 nm and 50 nm, respectively, is found when increasing the concentration. Emission spectra of SrMg.sub.2Al.sub.2N.sub.4:Eu with 0.1-5% (order curves from left to right: 0.1%; 0.2%; 0.5%; 1%; 2%; and 5% Eu, respectively) are shown in FIG. 6.

(52) Flux Variations

(53) For several systems fluxes were varied. Here below, results for SrMg.sub.3SiN.sub.4:Eu (1%) are described.

(54) A sample (1) was weighted in stoichiometrically and contains no SrF2 (as a reference sample): 0.99 SrH2+0.01 EuF3+3 Mg+Si. A sample (2) was weighed in with 20 (mol) % of the educt SrH2 exchanged for SrF2: 0.79 SrH2+0.01 EuF3+0.2 SrF2+3 Mg+Si. A sample (3) was weighted containing 20 mol % of SrF2 in addition to the same amount of SrH2 as in sample (1): 0.99 SrH2+0.01 EuF3+0.2 SrF2+3 Mg+Si. A sample (4) was weighted containing 40% of SrF2 additionally: 0.99 SrH2+0.01 EuF3+0.4 SrF2+3 Mg+Si.

(55) All four samples have been synthesized in a Hot Isostatic Press (HIP) in the same run, so they had the same temperature and pressure conditions and can be compared quite well. (The temperature in the HIP was raised with 150 C./h to 600 C., maintaining a N2-pressure of 3000 PSI (=207 bar). After two hours at 600 C., the temperature and pressure then have been raised with about 200 C./h to 1050 C. and 7500 PSI (=517 bar) respectively. After 5 h at 1050 C. the samples were cooled down again in 2.5 h to room temperature.)

(56) The efficiencies of the phosphor increases from sample (1) to sample (4).

(57) Further Data for Sr.sub.1xLiAl.sub.3N.sub.4:Eu.sub.x

(58) TABLE-US-00006 Eu Refl at LE FWHM Plpeak [mol %] 440 nm x y [lm/W] [nm] [nm] 0.05 0.499 0.695 0.305 86 52 651 0.20 0.394 0.705 0.295 72 52 653 1.00 0.268 0.712 0.288 58 53 655
Luminescence lifetime (monoexponential fit, no afterglow observed):

(59) TABLE-US-00007 Eu Decay time [mol %] [ns] 0.2 789 0.2 794 0.2 780 0.6 798 0.4 793
Thermal quenching measurement (450 nm excitation):

(60) TABLE-US-00008 T ( C.) 50 75 100 125 150 rel. Int. 1.00 1.00 0.99 0.98 0.97 T ( C.) 175 200 225 250 275 300 323 rel. Int. 0.95 0.92 0.89 0.85 0.81 0.75 0.69

(61) SrLiAl.sub.3N.sub.4:Eu.sup.2+ was also dispersed in a resin for a LED application with a blue emitting die (700 mA/mm.sup.2, 85 C.). Good results were obtained in terms of lifetime and thermal quenching. Especially the quenching temperature is very beneficial.