Abstract
A phosphor is disclosed. In an embodiment the phosphor includes an inorganic compound having at least one activator E and N and/or O in its empirical formula, wherein E is selected from the group consisting of Mn, Cr, Ni, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, Tm, Li, Na, K, Rb, Cs and combinations thereof, and wherein the inorganic compound crystallizes in a crystal structure with the same atomic sequence as in K.sub.2Zn.sub.6O.sub.7.
Claims
1-19. (canceled)
20. A phosphor comprising: an inorganic compound having at least one activator E and N and/or O in its empirical formula, wherein E is selected from the group consisting of Mn, Cr, Ni, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, Tm, Li, Na, K, Rb, Cs and combinations thereof, and wherein the inorganic compound crystallizes in a crystal structure with the same atomic sequence as in K.sub.2Zn.sub.6O.sub.7.
21. The phosphor according to claim 20, wherein the crystal structure is described in the orthorhombic space group Pnnm.
22. The phosphor according to claim 20, wherein the inorganic compound has one of the following general empirical formulae:
(AX.sub.aAY.sub.bAZ.sub.c)(BV.sub.dBW.sub.eBX.sub.fBY.sub.gBZ.sub.h)(CX.sub.nCY.sub.y):E or
(AX.sub.aAY.sub.bAZ.sub.c)(BV.sub.dBW.sub.eBX.sub.fBY.sub.gBZ.sub.h)(CX.sub.nCY.sub.y), wherein AX is selected from the group consisting of monovalent metals, wherein AY is selected from the group consisting of divalent metals, wherein AZ is selected from the group consisting of trivalent metals, wherein BV is selected from the group consisting of monovalent metals, wherein BW is selected from the group consisting of divalent metals, wherein BX is selected from the group consisting of trivalent elements, wherein BY is selected from the group consisting of tetravalent elements, wherein BZ is selected from the group consisting of pentavalent elements, wherein CX is selected from the group consisting of O, S, C, F, Cl, Br, I and combinations thereof, wherein CY=N, wherein E is selected from the group consisting of Mn, Cr, Ni, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, Tm, Li, Na, K, Rb, Cs and combinations thereof, and wherein:
1a+2b+3c+1d+2e+3f+4g+5h2n3y=z,
3<a+b+c<5,
10<d+e+f+g+h<14,
12<n+y<16 and
0.5z0.5.
23. The phosphor according to claim 22, wherein:
1a+2b+3c+1d+2e+3f+4g+5h2n3y=z,
a+b+c=4,
d+e+f+g+h=12,
n+y=14, and
0.1z0.1.
24. The phosphor according to claim 22, wherein z=0.
25. The phosphor according to claim 24, wherein the inorganic compound has one of the following empirical formulae:
M.sub.4Li.sub.1+y/2Al.sub.11y/2N.sub.14yO.sub.y:E, M.sub.4Li.sub.1zAl.sub.11zZn.sub.2zN.sub.14:E, M.sub.4Li.sub.1Al.sub.11xZn.sub.xN.sub.14xO.sub.x:E,
M.sub.4Li.sub.1Al.sub.11yMg.sub.yN.sub.14yO.sub.y:E, M.sub.4Li.sub.1+zAl.sub.113zSi.sub.2zN.sub.14:E or M.sub.4Li.sub.1Al.sub.112xSi.sub.xMg.sub.xN.sub.14:E, wherein M=Ca, Sr and/or Ba, and wherein:
0y14,
0z1,
0x11,
0y11,
0z3 and and
0x5.
26. The phosphor according to claim 25, wherein M=Sr.
27. The phosphor according to claim 20, wherein AX is selected from the group consisting of Li, Na, K, Rb, Cs and combinations thereof, wherein AY is selected from the group consisting of Mg, Ca, Sr, Ba, Eu, Yb, Mn, Ni and combinations thereof, wherein AZ is selected from the group consisting of Sc, Y, La, Pr, Ce, Yb, Cr and combinations thereof, wherein BV is selected from the group consisting of Li, Na and combinations thereof, wherein BW is selected from the group consisting of Mg, Zn, Mn, Ni and combinations thereof, wherein BX is selected from the group consisting of B, Al, Ga, Ce, Cr and combinations thereof, wherein BY is selected from the group consisting of Si, Ge, Mn and combinations thereof, wherein BZ=P, wherein CX is selected from the group consisting of O, S and combinations thereof, wherein CY=N, and wherein E is selected from the group consisting of Mn, Cr, Ni, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Yb, Tm, Li, Na, K, Rb, Cs and combinations thereof.
28. The phosphor according to claim 20, wherein the inorganic compound has one of the following empirical formulae:
M.sub.4xEu.sub.xLi.sub.1+y/2Al.sub.11y/2N.sub.14yO.sub.y, M.sub.4xEu.sub.xLi.sub.1zAl.sub.11zZn.sub.2zN.sub.14, M.sub.4xEu.sub.xLi.sub.1Al.sub.11xZn.sub.xN.sub.14xO.sub.x,
M.sub.4xEu.sub.xLi.sub.1Al.sub.11yMg.sub.yN.sub.14yO.sub.y, M.sub.4xEu.sub.xLi.sub.1+zAl.sub.113zSi.sub.2zN.sub.14 or M.sub.4xEu.sub.xLi.sub.1Al.sub.112xSi.sub.xMg.sub.xN.sub.14 wherein M=Ca, Sr and/or Ba, and
0y14,
0z1,
0x11,
0y11,
0z3,
0x5 and
0x2.
29. The phosphor according to claim 20, wherein the inorganic compound has the following empirical formula:
M.sub.4xEu.sub.xLiAl.sub.11N.sub.14, wherein M=Ca, Sr and/or Ba, and 0<x2.
30. The phosphor according to claim 20, wherein the phosphor has an emission maximum in a range from 500 to 680 nm.
31. The phosphor according to claim 20, wherein the phosphor has a dominant wavelength of >500 nm.
32. A method for producing the phosphor according to claim 20, the method comprising: mixing starting materials comprising Li.sub.3N, LiAlH.sub.4, Sr.sub.3N.sub.2, AlN and EuF.sub.3 or Li.sub.3N, LiAlH.sub.4, Sr.sub.3N.sub.2, AlN, SrH.sub.2 and EuF.sub.3; heating the mixture to a temperature of between 900 and 1400 C.; annealing the mixture at a temperature of 900 to 1400 C. for five minutes to six hours; and cooling the mixture to room temperature.
33. The method according to claim 32, wherein method comprises performing the method between heating the mixture and cooling the mixture under a gas atmosphere.
34. A conversion element comprising the phosphor according to claim 20.
35. The conversion element according to claim 34, wherein the conversion element is a conversion element for an LED.
36. A method for using the phosphor according to claim 20, the method comprising: converting incoming light, by the phosphor, into a longer-wave light.
37. A red-emitting phosphor comprising: an Eu.sup.2+-doped nitridoaluminate phosphor, wherein, in a X-ray powder diffractogram using CuK.sub.1 radiation, the red-emitting phosphor has two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2.
38. The red-emitting phosphor according to claim .sub.37, wherein a crystal structure of the Eu.sup.2+-doped nitridoaluminate phosphor has the same atomic sequence as in K.sub.2Zn.sub.6O.sub.7.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0116] Further advantageous embodiments and further developments of the invention are revealed by the exemplary embodiments described below in conjunction with the figures.
[0117] FIGS. 1, 4 and 7 show X-ray powder diffractograms using copper K.sub.1 radiation of three exemplary embodiments of a red-emitting phosphor;
[0118] FIGS. 2, 5 and 8 show emission spectra from three exemplary embodiments of a red-emitting phosphor;
[0119] FIGS. 3, 6 and 9 show reflectances from three exemplary embodiments of a red-emitting phosphor;
[0120] FIG. 10 shows an emission spectrum of an exemplary embodiment of a red-emitting phosphor;
[0121] FIG. 11 shows the reflectance of an exemplary embodiment of a red-emitting phosphor;
[0122] FIGS. 12A, 12B, 13A, 13B and 14 show an X-ray powder diffractogram using copper K.sub.1 radiation from an exemplary embodiment of a red-emitting phosphor;
[0123] FIG. 15 shows a portion of the crystal structure of a red-emitting phosphor;
[0124] FIGS. 16A, 16B and 16C show characteristic properties of a red-emitting phosphor;
[0125] FIG. 17 shows the emission spectra from three substitution variants based on Sr.sub.4Eu.sub.xLiAl.sub.11N.sub.14; and
[0126] FIGS. 18A and 18B show a selection of possible, electroneutral empirical formulae for substitution experiments.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0127] FIG. 1 shows three X-ray powder diffractograms using copper K.sub.1 radiation. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The X-ray powder diffractogram provided with reference sign I shows that of a first exemplary embodiment of the red-emitting phosphor according to the invention. It has two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2. These characteristic reflections of the red-emitting phosphor according to the invention have a relative intensity compared to the strongest reflection in the X-ray powder diffractogram of over 2% (absolute intensity) or over 1% (integral intensity). The intensity of these reflections is at least three times as great as the average noise in the X-ray powder diffractogram and the reflections are thus significant reflections, which may be associated with the red-emitting phosphor. The X-ray powder diffractogram provided with reference sign II corresponds to that of the known phosphor of formula SrLiAl.sub.3N.sub.4:Eu.sup.2+. As is apparent, this known phosphor does not show the characteristic reflections of the red-emitting phosphor according to the invention in the angular range of 11.5-12.5 2 and in the angular range of 18.5-19.5 2. The X-ray powder diffractogram provided with reference sign III is a simulated diffractogram of a compound of formula SrLiAl.sub.3N.sub.4. It is clear from the X-ray powder diffractograms shown that the red-emitting phosphor according to the invention is a phosphor which differs from the known phosphor of formula SrLiAl.sub.3N.sub.4:Eu.sup.2+. This is also proven by the additional reflections in an angular range of 11.5-12.5 2 and in the angular range of 18.5-19.5 2 of the red-emitting phosphor according to the invention compared with the known phosphor. The phosphor according to the invention comprises the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+ and additionally also one further phase of an Eu.sup.2+-doped nitridoaluminate phosphor of empirical formula Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0128] The first exemplary embodiment of the phosphor according to the invention, which has the X-ray powder diffractogram with the reference sign I in FIG. 1, was produced as follows: 0.0591 mol Sr.sub.3N.sub.2, 0.0297 Li.sub.3N, 0.089 mol LiAlH.sub.4, 0.445 mol AlN and 0.0007 mol EuF.sub.3 are mixed together homogeneously. The molar ratio AlN:Sr.sub.3N.sub.2:Li.sub.3N:LiAlH.sub.4:EuF.sub.3 is 1:0.1328:0.0667:0.2:0.0016. The mixture is transferred into a tungsten crucible, which is transferred into a tube furnace. Under a forming gas atmosphere (N.sub.2:H.sub.2=92.5:7.5) the mixture is heated at a heating rate of 250 C. per hour to a temperature of 1250 C. The mixture is annealed for 15 minutes at a temperature of 1250 C., and then cooling to 1000 C. proceeds at a cooling rate of 170 C. per hour. The mixture is held for 15 minutes at 1000 and then cooled to room temperature at a cooling rate of 250 C. per hour.
[0129] FIG. 2 shows the emission spectrum of the first exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 1. The wavelength in nanometers is plotted on the x axis and the emission intensity in per cent is plotted on the y axis. To measure the emission spectrum, the phosphor according to the invention was excited with blue light of a wavelength of 460 nm. The phosphor has a half-value width of 59 nm and a dominant wavelength of 627 nm, the emission maximum being at about 654 nm. Compared with the known phosphors (Sr,Ba).sub.2Si.sub.5N.sub.8:Eu.sup.2+ with a half-value width of greater than 90 nm and (Sr,Ca)AlSiN.sub.3:Eu.sup.2+ with a half-value width of greater than 70 nm, the phosphor according to the invention thus has a smaller half-value width. The phosphor according to the invention thus emits virtually only in the visible range of the electromagnetic spectrum, which leads to a reduction in losses in the IR region. The known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+ has a half-value width of about 50 nm, but in comparison with the phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+ the quantum efficiency of the phosphor according to the invention is higher.
[0130] FIG. 3 shows the reflectance of the first exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 1, as a function of wavelength. The wavelength in nanometers is plotted on the x axis and the reflectance in per cent is plotted on the y axis. As is apparent, the phosphor according to the invention has a minimum reflectance between 450 and 500 nm and is thus best excited with a wavelength of between 450 and 500 nm, since absorption is particularly high at this wavelength. Compared to the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+, the phosphor according to the invention has a higher absorption in the range from 450 nm to 500 nm.
[0131] FIG. 4 shows three X-ray powder diffractograms using copper K.sub.1 radiation. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The X-ray powder diffractogram provided with reference sign I shows that of a second exemplary embodiment of the red-emitting phosphor according to the invention. Like the first exemplary embodiment, it has two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2. In comparison with the first exemplary embodiment, the intensity of the characteristic reflections is higher. The X-ray powder diffractogram provided with reference sign II shows that of the known phosphor of formula SrLiAl.sub.3N.sub.4:Eu.sup.2+. As in FIG. 1, it is here also apparent that the known phosphor does not have the characteristic reflections of the phosphor according to the invention in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2. The X-ray powder diffractogram provided with reference sign III is a simulated diffractogram of a compound of formula SrLiAl.sub.3N.sub.4.
[0132] The second exemplary embodiment of the phosphor according to the invention, the X-ray powder diffractogram of which is shown in Figure .sub.4 with reference sign I, was produced as follows: 0.0509 mol Sr.sub.3N.sub.2, 0.0383 Li.sub.3N, 0.0383 mol LiAlH.sub.4, 0.4216 mol AlN and 0.0006 mol EuF.sub.3 are processed into a homogeneous mixture. The molar ratio AlN:Sr.sub.3N.sub.2:Li.sub.3N:LiAlH.sub.4:EuF.sub.3 is 1:0.1207:0.0908:0.0908:0.0014. The mixture is transferred into a tungsten crucible, which is transferred into a tube furnace. Under a forming gas atmosphere (N.sub.2:H.sub.2=92.5:7.5), the mixture is heated at a heating rate of 250 C. per hour to a temperature of 1250, held for one hour at this temperature and then cooled to room temperature at a cooling rate of 250 C. per hour. The phosphor according to the invention of the second exemplary embodiment comprises the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+ and additionally also one further phase of an Eu.sup.2+-doped nitridoaluminate phosphor of empirical formula Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0133] FIG. 5 shows the emission spectrum of the second exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 4. The wavelength in nanometers is plotted on the x axis and the emission intensity in per cent is plotted on the y axis. To measure the emission spectrum, the phosphor according to the invention was excited with blue light of a wavelength of 460 nm. The phosphor has a half-value width of 61 nm and a dominant wavelength of 627 nm, the emission maximum being at about 654 nm.
[0134] FIG. 6 shows the reflectance of the second exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 4, as a function of wavelength. The wavelength in nanometers is plotted on the x axis and the reflectance in per cent is plotted on the y axis. As is apparent, the phosphor according to the invention has a minimum reflectance between 450 and 500 nm and is thus best excited with a wavelength of between 450 and 500 nm, since absorption is particularly high at this wavelength. In comparison with the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+, the second exemplary embodiment of the phosphor according to the invention also has a higher absorption in the range from 450 nm to 500 nm.
[0135] FIG. 7 shows three X-ray powder diffractograms using copper K.sub.1 radiation. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The X-ray powder diffractogram provided with reference sign I shows that of a third exemplary embodiment of the red-emitting phosphor according to the invention. Like the first and second exemplary embodiments, it has two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2. In comparison with the first and second exemplary embodiments, the intensity of the characteristic reflections is greater. The X-ray powder diffractogram provided with reference sign II shows that of a phosphor of formula SrLiAl.sub.3N.sub.4:Eu.sup.2+. As in FIGS. 1 and 4, it is here also apparent that the known phosphor does not have the characteristic reflections of the phosphor according to the invention in an angular range of 11.5-12.5 2 and in the range 18.5-19.5 2. The X-ray powder diffractogram provided with reference sign III is a simulated diffractogram of a compound of formula SrLiAl.sub.3N.sub.4. The phosphor according to the invention of the third exemplary embodiment comprises the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+ and additionally also one further phase of an Eu.sup.2+-doped nitridoaluminate phosphor of empirical formula Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0136] The third exemplary embodiment of the phosphor according to the invention, the X-ray powder diffractogram of which is shown in FIG. 7 with reference sign I, was produced as follows: 0.0591 mol Sr.sub.3N.sub.2, 0.0297 Li.sub.3N, 0.089 mol LiAlH.sub.4, 0.445 mol AlN and 0.0007 mol EuF.sub.3 were processed into a homogeneous mixture. The molar ratio AlN:Sr.sub.3N.sub.2:Li.sub.3N:LiAlH.sub.4:EuF.sub.3 is 1:0.1328:0.0667:0.20:0.0016. The mixture is transferred into a tungsten crucible, which is transferred into a tube furnace. Under a forming gas atmosphere (N.sub.2:H.sub.2=92.5:7.5), the mixture is heated at a heating rate of 250 C. per hour to a temperature of 1250 , held for five hours at this temperature and then cooled to room temperature at a cooling rate of 250 C. per hour.
[0137] FIG. 8 shows the emission spectrum of the third exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 7. The wavelength in nanometers is plotted on the x axis and the emission intensity in per cent is plotted on the y axis. To measure the emission spectrum, the phosphor according to the invention was excited with blue light of a wavelength of 460 nm. The phosphor has a half-value width of 68 nm and a dominant wavelength of 625 nm, the emission maximum being at about 652 nm.
[0138] FIG. 9 shows the reflectance of the third exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 7, as a function of wavelength. The wavelength in nanometers is plotted on the x axis and the reflectance in per cent is plotted on the y axis. As is apparent, the phosphor according to the invention has a minimum reflectance between 450 and 500 nm and is thus best excited with a wavelength of between 450 and 500 nm, since absorption is particularly high at this wavelength. In comparison with the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+, a higher absorption in the range from 450 nm to 500 nm may also be shown for the third exemplary embodiment of the phosphor according to the invention.
[0139] Overall, it is clear from the three exemplary embodiments of the red-emitting phosphor according to the invention that by varying the temperature T1, the duration of method step C) and/or the molar ratios of the starting materials, the half-value width of the red-emitting phosphor or the composition of the red-emitting phosphor may be varied. In summary, the three exemplary embodiments have the following half-value widths and dominant wavelengths:
TABLE-US-00001 FWHM/nm .sub.dom/nm First exemplary embodiment 59 627 Second exemplary embodiment 61 627 Third exemplary embodiment 68 625
[0140] FIG. 10 shows the emission spectrum of a fourth exemplary embodiment of the red-emitting phosphor according to the invention. The wavelength in nanometers is plotted on the x axis and the emission intensity in per cent is plotted on the y axis. To measure the emission spectrum, the phosphor according to the invention in the form of a powder tablet was excited with blue light of a wavelength of 460 nm. The phosphor has a half-value width of 85 nm and a dominant wavelength of 623.5 nm, the emission maximum being at 670 nm.
[0141] The fourth exemplary embodiment of the phosphor according to the invention was produced as follows: 161.75 mmol Sr.sub.3N.sub.2, 485.26 mmol SrH.sub.2, 828.27 mmol LiAlH.sub.4 48.72 mmol Li.sub.3N, 1843.60 mmol AlN and 3.90 mmol EuF.sub.3 were processed into a homogeneous mixture. The molar ratio AlN:Sr.sub.3N.sub.2:SrH.sub.2:LiAlH.sub.4:Li.sub.3N:EuF.sub.3 is 1:0.088:0.263:0.449:0.026:0.002. The mixture is transferred into a tungsten crucible, which is in turn transferred into a tube furnace. Under a forming gas atmosphere (N.sub.2:H.sub.2=92.5:7.5), the mixture is heated at a heating rate of 250 C. per hour to a temperature of 1400, held for 15 minutes at this temperature and then cooled to room temperature at a cooling rate of 250 C. per hour. The phosphor has the empirical formula Sr.sub.4LiAl.sub.11N.sub.14:Eu.sup.2+, wherein Eu.sup.2+ partly replaces Sr. This can alternatively be written Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14. The red-emitting phosphor or the Eu.sup.2+-doped nitridoaluminate phosphor crystallizes in a crystal structure with the same atomic sequence as in K.sub.2Zn.sub.6O.sub.7. The crystal structure may in particular be described in the orthorhombic space group Pnnm. In particular, the lattice parameters in the orthorhombic description with the space group Pnnm are a=10.4291(7) , b=10.4309(7) and c=3.2349(2) and ===90. Descriptions in other space groups are also possible.
[0142] FIG. 11 shows the reflectance of the fourth exemplary embodiment of the phosphor according to the invention, which was synthesized as described in relation to FIG. 10, as a function of wavelength. The wavelength in nanometers is plotted on the x axis and the reflectance in per cent is plotted on the y axis. As is apparent, the phosphor according to the invention has a minimum reflectance between 450 and 500 nm and is thus best excited with a wavelength of between 450 and 500 nm, since absorption is particularly high at this wavelength. In comparison with the known phosphor SrLiAl.sub.3N.sub.4:Eu.sup.2+, a higher absorption in the range from 450 nm to 500 nm may also be shown for the fourth exemplary embodiment of the phosphor according to the invention.
[0143] FIG. 12A shows the X-ray powder diffractogram using copper K.sub.1 radiation of the fourth exemplary embodiment, which was synthesized as described in relation to FIG. 10. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The fourth exemplary embodiment also has two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2.
[0144] FIG. 12B shows a portion of the X-ray powder diffractogram from FIG. 12A. Here again, the two characteristic reflections in an angular range of 11.5-12.5 2 and in an angular range of 18.5-19.5 2 are clearly apparent.
[0145] FIG. 13A shows two X-ray powder diffractograms using copper Km radiation. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The X-ray powder diffractogram provided with reference sign I shows that of the fourth exemplary embodiment of the red-emitting phosphor according to the invention. The X-ray powder diffractogram provided with reference sign II shows that of a phosphor of formula SrLiAl.sub.3N.sub.4:Eu.sup.2+. As in FIGS. 1 and 4 and 7, it is here also apparent that the known phosphor does not have the characteristic reflections of the phosphor according to the invention in an angular range of 11.5-12.5 2 and in the range 18.5-19.5 2.
[0146] FIG. 13B shows a portion of the X-ray powder diffractogram of FIG. 13A.
[0147] FIG. 14 shows two X-ray powder diffractograms using copper K.sub.1 radiation. The diffraction angles are plotted on the x axis in 2 values and the intensity is plotted on the y axis. The X-ray powder diffractogram provided with reference sign I shows that the measured X-ray powder diffractogram of the fourth exemplary embodiment of the red-emitting phosphor according to the invention. The diffractogram provided with reference sign IV corresponds to the X-ray powder diffractogram calculated from single crystal data for the phosphor according to the invention of formula Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14. The reflections marked * should be assigned to a secondary phase of AlN. This may also result from the starting material or possibly also be attributable to partial decomposition of the phosphor. As is apparent, the match between the measured X-ray powder diffractogram with the reference sign I and the calculated diagram with the reference sign VI is very high.
[0148] FIG. 15 shows the orthorhombic crystal structure of the phosphor Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14 in a schematic diagram. The phosphor crystallizes orthorhombically in the space group Pnnm. The structure of the phosphor was determined on the basis of single crystal diffraction data. The structure has corner-linked and edge-linked (Al,Li)N-tetrahedra. Sr atoms are arranged amongst the network of tetrahedra. Descriptions in other space groups are also possible. The phosphor according to the invention thus has the same atomic sequence as K.sub.2Zn.sub.6O.sub.7.
[0149] FIG. 16A shows crystallographic data of Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0150] FIG. 16B shows atomic layers in the structure of Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0151] FIG. 16C shows anisotropic displacement parameters for Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14.
[0152] FIG. 17 shows the emission spectra of three substitution variants of the phosphor Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14. Substitution variants should here be understood to mean that in these phosphors the elements Sr, Eu, Li, Al and/or N in the empirical formula Sr.sub.4xEu.sub.xLiAl.sub.11N.sub.14 are in part replaced by other elements. The wavelength in nanometers is plotted on the x axis and the emission intensity E in per cent is plotted on the y axis. To measure the emission spectrum, the samples in the form of individual crystals were excited with blue light of a wavelength of 460 nm. By varying the composition, while preserving the half-value width, i.e., while preserving the atomic sequences, it is possible to achieve a significant shift in the emission bands towards shorter wavelengths, leading to a further increase in the overlap with the sensitivity of the eye and thus more efficient phosphors. The phosphor, which has the emission with reference sign A, shows in EDX measurements an Al:Si molar ratio of about 1:1 and has a peak wavelength of 636 nm and is thus markedly blueshifted compared with the unsubstituted phosphor Sr.sub.4LiAl.sub.11N.sub.14:Eu.sup.2+, which has a peak wavelength at 670 nm.
[0153] FIGS. 18A and 18B show tables with possible, electroneutral compounds, which may be achieved by substitution experiments, as with general empirical formula (AX.sub.aAY.sub.bAZ.sub.c)(BV.sub.dBW.sub.eBX.sub.fBY.sub.gBZ.sub.h)(CX.sub.nCY.sub.y):E. The substitutions shown are merely exemplary, other substitutions are likewise possible while preserving the crystal structure.
[0154] The description made with reference to exemplary embodiments does not restrict the invention to these embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or exemplary embodiments.
