LUMINOPHORE, METHOD FOR PRODUCING A LUMINOPHORE AND RADIATION-EMITTING COMPONENT

Abstract

A luminophore may have the general formula A.sub.2EZ.sub.zX.sub.x:RE,

where: A is selected from the group of the monovalent elements; E is selected from the group of the tetravalent, pentavalent, or hexavalent elements; Z is selected from the group of the divalent elements; X is selected from the group of the monovalent elements; RE is selected from activator elements; 2+e=2z+x, with the charge number e of the element E; and x+z=5 and z>0.

A process is also disclosed that is directed to producing the luminophore and a corresponding radiation-emitting component.

Claims

1. A luminophore having the general formula A.sub.2EZ.sub.zX.sub.x:RE where: A is selected from the group of the monovalent elements; E is selected from the group of the tetravalent, pentavalent, or hexavalent elements; Z is selected from the group of the divalent elements; X is selected from the group of the monovalent elements; RE is selected from activator elements; 2+e=2z+x, with the charge number e of the element E; and x+z=5 and z>0.

2. The luminophore as claimed in claim 1, wherein the luminophore has the formula A.sub.2EO.sub.zF.sub.x:RE.

3. The luminophore as claimed in claim 1, wherein A is selected from Li, Na, K, Rb, Cs, and combinations thereof; wherein E is selected from Sn, Si, Ge, Ti, Zr, Hf, Pb, V, W, Mo, and combinations thereof; wherein RE is selected from Mn, Eu, Ce, and combinations thereof; and combinations thereof.

4. The luminophore as claimed in claim 1, wherein RE has a molar proportion ranging from 0.001 to 0.1 inclusive, based on element E.

5. The luminophore as claimed in claim 1, wherein the luminophore has the formula K.sub.2SnOF.sub.4:RE, or wherein the luminophore has the formula K.sub.2WO.sub.3F.sub.2:RE.

6. The luminophore as claimed in claim 1, wherein the luminophore has a host structure that crystallizes in an orthorhombic space group.

7. The luminophore as claimed in claim 1, wherein the luminophore has a host structure comprising [E(Z,X).sub.6].sup.4− octahedra linked via common Z atoms to give strands.

8. The luminophore (1) as claimed in claim 7, wherein the strands composed of linked [E(Z,X).sub.6].sup.4− octahedra form interspaces, wherein there is an A element at least in one interspace.

9. The luminophore as claimed in claim 1, wherein an emission spectrum of the luminophore has a multitude of emission peaks ranging from 590 nanometers to 700 nanometers.

10. The luminophore as claimed in claim 1, wherein a half-height width of an emission peak of the luminophore ranges from 1 nanometer to 15 nanometers inclusive.

11. The luminophore as claimed in claim 1, wherein an emission maximum of an emission peak of the luminophore ranges from 626 nanometers to 635 nanometers inclusive.

12. A process for producing a luminophore having the general formula A.sub.2EZ.sub.zX.sub.x:RE, where: A is selected from the group of the monovalent elements; E is selected from the group of the tetravalent, pentavalent, or hexavalent elements; Z is selected from the group of the divalent elements; X is selected from the group of the monovalent elements; RE is selected from activator elements; 2+e=2z+x, with the charge number e of the element E; x+z=5 and z>0; wherein the method comprises: synthesizing the host material; and doping the host material.

13. The process for producing a luminophore as claimed in claim 12, wherein the synthesis of the host material comprises: providing a composition of reactants; and heating the composition of reactants to a maximum temperature ranging from 150° C. to 1000° C. inclusive at a maximum pressure ranging from 0.55 GPa to 7.50 GPa inclusive.

14. The process for producing a luminophore as claimed in claim 12, wherein the doping of the host material comprises: providing a composition of host material and dopant; and grinding the composition of host material and dopant.

15. The process for producing a luminophore as claimed claim 12, wherein no hydrofluoric acid solution is used.

16. A radiation-emitting component comprising: a semiconductor chip configured to emit electromagnetic radiation from a first wavelength range; a conversion element including a luminophore having the general formula A.sub.2EZ.sub.zX.sub.x:RE that converts electromagnetic radiation of the first wavelength range to electromagnetic radiation of a second wavelength range; wherein: A is selected from the group of the monovalent elements; E is selected from the group of the tetravalent, pentavalent, or hexavalent elements; Z is selected from the group of the divalent elements; X is selected from the group of the monovalent elements; RE is selected from activator elements, 2+e=2z+x, with the charge number e of the element E; and x+z=5 and z>0.

17. The radiation-emitting component as claimed in claim 16, wherein the luminophore emits in the red spectral region.

18. The radiation-emitting component as claimed in claim 16, wherein the conversion element comprises at least one further luminophore configured to convert electromagnetic radiation of the first wavelength range to electromagnetic radiation of a third wavelength range.

19. The radiation-emitting component as claimed in claim 18, wherein the conversion element comprises a further luminophore configured to emit in the green spectral region.

20. The radiation-emitting component (10) as claimed in claim 16, wherein the conversion element is free of any further luminophore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Further advantageous embodiments, configurations and developments of the luminophore, of the process for producing a luminophore and of the radiation-emitting component will be apparent from the working examples that follow, which are described in conjunction with the figures.

[0107] FIG. 1A shows a detail of the host structure of the comparative example K.sub.2SiF.sub.6,

[0108] FIGS. 1B and 1C each show a detail of the host structure of the luminophore in different working examples,

[0109] FIGS. 2A and 2B show powder x-ray diffractograms (PXRD) of the host structure of the luminophore and of the luminophore in different working examples,

[0110] FIG. 3 shows an emission spectrum of the luminophore in one working example,

[0111] FIG. 4A shows the comparison of emission spectra of a working example and a comparative example,

[0112] FIG. 4B shows the comparison of spectral efficiency of a working example and a comparative example, and

[0113] FIG. 5 shows a radiation-emitting component in one working example.

[0114] Elements that are the same, of the same type or have the same effect are given the same reference numerals in the figures. The figures and the size ratios of the elements shown in the figures relative to one another should not be considered to be to scale. Instead, individual elements, especially layer thicknesses, may be represented in excessively large size for better representability and/or for better understanding.

DETAILED DESCRIPTION

[0115] FIG. 1A shows a detail of the host structure of the comparative example K.sub.2SiF.sub.6. The host structure of the comparative example K.sub.2SiF.sub.6 crystallizes in the cubic Fm-3m space group (no. 225). In the unit cell of the crystal structure of the comparative example K.sub.2SiF.sub.6, [SiF.sub.6].sup.2− octahedra 2 are present exclusively in spatially isolated form.

[0116] The working examples of the host structures K.sub.2SnOF.sub.4 (FIG. 1B) and K.sub.2WO.sub.3F.sub.2 (FIG. 1C), by contrast, crystallize in the orthorhombic space group Pnma (no. 62). In the unit cells of the working examples, there are ordered [SnO.sub.2F.sub.4].sup.4− octahedra 5 and [WO.sub.4F.sub.2].sup.4− octahedra 9 that are linked via common oxygen atoms 6 to give infinite strands 7. In other words, in the crystal structure, there are thus [SnO.sub.2/2F.sub.4].sup.2− octahedra 5 and [WO.sub.2/2 (O.sub.2F.sub.2)].sup.2− octahedra 9 that are linked via oxygen atoms 6 to give strands 7.

[0117] The [SnO.sub.2F.sub.4].sup.4− octahedra 5 in FIG. 1B are formed by two oxygen atoms 6 and four fluorine atoms 3. The two oxygen atoms 6 occupy two opposite vertices of the octahedron via which the octahedra are linked to one another. The four further vertices of the octahedron are occupied by fluorine atoms 3. The Sn atom is arranged within the octahedron.

[0118] The [WO.sub.4F.sub.2].sup.4− octahedra 9 in FIG. 1C are formed by four oxygen atoms 6 and two fluorine atoms 3. Two oxygen atoms 6 occupy two opposite vertices of the octahedron via which the octahedra are joined to one another. The four further vertices of the octahedron are occupied by a mixture of oxygen atoms and fluorine atoms 3 and 6 (50% each). The W atom is arranged within the octahedron.

[0119] The strands 7 are arranged parallel to one another and run along the vertical edges of the unit cell along the crystallographic b axis or along [010], and vertically through the middle of the unit cell along [010]. The strands 7 are not linked to one another either directly or indirectly. Between the strands 7, interspaces 8 are formed, in which potassium atoms 4 are present. The crystal structure, the formation units and the linkage patterns thereof are thus similar to those in (NH.sub.4).sub.2FeF.sub.5.

[0120] The working example K.sub.2SnOF.sub.4:Mn.sup.4+ of the luminophore 1 was synthesized as follows: the reactants SnO.sub.2 and KHF.sub.2 were weighed out in a molar ratio of 1:2.5. The reactant KHF.sub.2 was thus in excess.

[0121] The reactants were put under a maximum pressure of 2.5 GPa (25 kbar) in a multianvil high-pressure press. The pressure was built up within 65 minutes. Subsequently, the reactants were heated to a maximum temperature of 350° C. with the following temperature program: proceeding from room temperature (RT), the temperature was increased in steps of 32.5° C. per minute to 350° C. Subsequently, the temperature was maintained for 60 minutes. The subsequent cooling of the reaction mixture was effected in steps of 8.125° C. per minute from 350° C. to 25° C. The subsequent reduction of pressure was effected within 200 minutes.

[0122] This was followed by doping of the resultant host material K.sub.2SnOF.sub.4 in a ball mill. The K.sub.2SnOF.sub.4 host material was admixed with the K.sub.2MnF.sub.6 dopant in a molar ratio of 1:0.042 and ground 6 times at 300 rpm for 10 minutes. There was a break for 15 minutes between the grinding steps.

[0123] The host material of the working example K.sub.2WO.sub.3F.sub.2 was synthesized as follows: the KF and WO.sub.3 reactants were weighed out in a molar ratio of 2:1. The reactants were thus in a stoichiometric ratio.

[0124] The reactants were put under a maximum pressure of 5.5 GPa (55 kbar) in a multianvil high-pressure press. The pressure was built up within 145 minutes. Subsequently, the reactants were heated to a maximum temperature of 900° C. with the following temperature program: proceeding from room temperature (RT), the temperature was increased to 900° C. in steps of 87.5° C. per minute. Subsequently, the temperature was maintained for 60 minutes. The subsequent cooling of the reaction mixture was effected in steps of 18.33° C. per minute from 900° C. to 350° C. Cooling from 350° C. to room temperature was then effected by switching off the heating power. The subsequent reduction of pressure was effected within 430 minutes.

[0125] Tab. 1 below shows the crystallographic data of the host structures of the working examples K.sub.2SnOF.sub.4 and K.sub.2WO.sub.3F.sub.2 of the luminophore 1. In the orthorhombic space group, the angles α, β and γ are 90°.

[0126] Tab. 1 reports the measured section of reciprocal space via the boundaries of the corresponding Miller indices (hkl). As a quality feature reported for the structural refinement, i.e. for the agreement of calculated and measured structure factors F (F.sup.2=reflection intensity I) with inclusion of further parameters, the goodness of fit (GoF) is reported, which should be close to 1. In addition, R1/wR2 [I≥2σ(I)] and R1/wR2 [all data] are reported, which should be as close as possible to 0. These are likewise goodness factors for the agreement of F or F.sup.2 “measured” with “calculated”. For R1/wR2 [I≥2σ(I)], only reflections having an intensity greater than 2× the average error of the determination of intensity itself are considered. For R1/wR2 [all data], all reflections are considered. R1 here is a measure of the general quality in relation to F and tends to 0. wR2 takes account of further parameters and relates to F.sup.2.

[0127] The goodness factor, and also R1/wR2 [I≥2σ(I)] and R1/wR2 [all data], are within the desired range for both working examples K.sub.2SnOF.sub.4 and K.sub.2WO.sub.3F.sub.2.

TABLE-US-00001 TABLE 1 Empirical formula K.sub.2SnOF.sub.4 K.sub.2WO.sub.3F.sub.2 Crystal system orthorhombic orthorhombic Space group Pnma (no. 62) Pnma (no. 62) a/pm 612.35(2) 607.71(3) b/pm 738.35(3) 735.19(3) c/pm 1082.94(5) 1077.38(5) Cell volume V/nm.sup.3 0.4896(1) 0.4814(1) Z 4 4 Packing density ρ/g × cm.sup.−3 3.919 4.803 T/K 173(2) 183(2) Diffractometer BRUKER D8 Quest BRUKER D8 Quest Radiation/Å Mo—Kα (0.71073) Mo—Kα (0.71073) Measurement range/° 6.7 < 2θ < 75.7 6.7 < 2θ < 70 −10 < h < 10 −9 < h < 9 −11 < k < 11 −11 < k < 11 −18 < l < 18 −17 < l < 17 R.sub.1/wR.sub.2 [I ≥ 2σ(I)] 0.0153/0.0377 0.0148/0.0335 R.sub.1/wR.sub.2 [all data] 0.0205/0.0397 0.0179/0.0343 GoF 1.065 1.163

[0128] FIG. 2A shows a powder x-ray diffractogram (PXRD) of the undoped host material K.sub.2SnOF.sub.4 of the working example K.sub.2SnOF.sub.4:Mn.sup.4+ of the luminophore 1 (top) compared to a simulation based on single-crystal data (bottom). FIG. 2B shows a powder x-ray diffractogram of the working example K.sub.2SnOF.sub.4:Mn.sup.4+ of the luminophore 1 after doping (top) compared to an image before the grinding operation (bottom). The plot in each case is of intensity I against diffraction angle 2θ in degrees. Mo-Kai radiation was used for the taking of the diffractograms. The powder x-ray diffractograms show that the luminophore 1 can be produced in good quality and is unchanged even after ball milling.

[0129] FIG. 3 shows an emission spectrum of the working example K.sub.2SnOF.sub.4:Mn.sup.4+ of the luminophore 1 after excitation with blue laser light having an excitation wavelength of 448 nm. The plot is of relative intensity I in % against wavelength A in nm. The emission spectrum shows a line spectrum having a multitude of narrow bands in the wavelength range between 590 nm and 660 nm and hence within the red wavelength range. The emission maximum of the most intense emission band of the luminophore 1 is at about 630.5 nm. Overall, the emission spectrum of FIG. 3 shows at least four emission bands having a relative intensity of more than 25%.

[0130] FIG. 4A shows a comparison of the emission spectra of the working example K.sub.2SnOF.sub.4:Mn.sup.4+ of the luminophore 1 (4-1) with the emission spectrum of the comparative example K.sub.2SiF.sub.6:Mn.sup.4+ (4-2), in each case after excitation with blue laser light having an excitation wavelength of 448 nm. Overall, it is possible to detect a high degree of agreement in terms of number and shape of the individual peaks. However, the emission spectrum of the luminophore 1 (4-1) has a small shift in emission to shorter wavelengths and an additional emission band at about 622 nm. In the cubic comparative luminophore (4-2), the corresponding transition is disallowed on symmetry grounds because of the octahedral Mn environments. As a result of the loss of symmetry with respect to the orthorhombic crystal system of the luminophore 1, the perfect octahedral symmetry is broken, as a result of which the corresponding transition is allowed by symmetry.

[0131] Tab. 2 below compares optical properties of the luminophore 1 (4-1) and of the comparative example (4-2).

TABLE-US-00002 TABLE 2 x, y LER/ Rel. λ.sub.dom/nm λ.sub.max/nm coordinates lmWopt.sup.− 1 LER/% 4-1 620.5 630.5 0.693(1); 217 106 0.307(1) 4-2 621 631 0.693(1); 204 100 0.307(1)

[0132] Given a comparable dominant wavelength λ.sub.dom and a comparable emission maximum λ.sub.max and an identical color locus (x,y coordinates), the luminophore K.sub.2SnOF.sub.4:Mn.sup.4+ has a higher spectral efficiency at 217 lmW.sub.opt.sup.−1 than the comparative example K.sub.2SiF.sub.6:Mn.sup.4+ at 204 lmW.sub.opt.sup.−1. The relative spectral efficiency of the luminophore K.sub.2SnOF.sub.4:Mn.sup.4+ is elevated by 6 percentage points compared to the comparative example K.sub.2SiF.sub.6:Mn.sup.4+ (tab. 2 and FIG. 4B). The rise in efficiency may be the result of the fact that the eye sensitivity curve has a large negative slope in the region of the emission maximum of the luminophore K.sub.2SnOF.sub.4:Mn.sup.4+, as a result of which even small additional signals result in a distinctly different spectral efficiency on the short-wave side of the emission maximum, such as the additional emission band at about 622 nm.

[0133] FIG. 5 shows a schematic section diagram of a radiation-emitting component 10. The radiation-emitting component 10 comprises a semiconductor chip 11 with an active layer sequence and an active region (not shown here explicitly), which emits primary radiation in operation of the radiation-emitting component 10. The primary radiation may be electronic radiation in the ultraviolet or blue region. For example, the semiconductor chip 11 is a semiconductor diode chip that emits primary radiation with wavelengths from 430 nm to 500 nm inclusive. Alternatively, the semiconductor chip 11 may be a laser diode chip which, for example, emits primary radiation with a wavelength of 448 nm. The primary radiation is emitted via the radiation exit surface 12 and forms a beam path.

[0134] The radiation-emitting component 10 further comprises a conversion element 13 which is set up to absorb the primary radiation and to convert at least partly to secondary radiation. The secondary radiation at least partly has a wavelength range with longer wavelengths than the primary radiation. For example, the conversion element 13 converts the primary radiation to secondary radiation in the red wavelength region.

[0135] The conversion element 13 is disposed in the beam path of the primary radiation of the semiconductor chip 11 such that at least some of the primary radiation hits the conversion element. For this purpose, the conversion element 13 may be applied in direct contact atop the semiconductor chip 11, especially the radiation exit surface 12, or be arranged spaced apart from the semiconductor chip 11.

[0136] The conversion element 13 includes a luminophore 1 having the general formula A.sub.2EZ.sub.zX.sub.x:RE. In particular, the conversion element 13 may include the luminophore 1 having the formula K.sub.2SnOF.sub.4:Mn.sup.4+. The luminophore 1 may be embedded into a matrix material. Alternatively, the conversion element 13 may be free of any matrix material and consist of the luminophore 1, for example of a ceramic of the luminophore 1.

[0137] The conversion element 13 may be free of any further luminophore. In that case, the radiation-emitting component 10 generates red light.

[0138] Alternatively, the conversion element 13 may include at least one further luminophore that converts the primary radiation or secondary radiation to radiation having an at least partly different wavelength range than the secondary radiation. For example, the conversion element 13 may include a green-emitting further luminophore or a yellow-emitting further luminophore, as a result of which white mixed light can be generated in combination with blue primary radiation. For rendering of large color spaces, the conversion element may especially contain the green luminophore β-SiAlON and the luminophore 1 having the formula K.sub.2SnOF.sub.4:Mn.sup.4+.

[0139] Alternatively, the conversion element 13 may include at least two further luminophores selected, for example, from green, yellow, orange or red luminophores, by means of which it is likewise possible to generate white mixed light.

[0140] The features and working examples described in conjunction with the figures may be combined with one another in further working examples, even if not all combinations are described explicitly. In addition, the working examples described in conjunction with the figures may alternatively or additionally have further features according to the description in the general part.

[0141] The invention is not limited to the working examples by the description with reference thereto. Instead, the invention encompasses any new feature and any combination of features, which especially includes any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or working examples.

LIST OF REFERENCE NUMERALS

[0142] 1 luminophore [0143] 2 [SiF.sub.6].sup.2− octahedron [0144] 3 F atom [0145] 4 K atom [0146] 5 [SnO.sub.2F.sub.4].sup.4− octahedron or [SnO.sub.2/2F.sub.4].sup.2− octahedron [0147] 6 O atom [0148] 7 strand [0149] 8 interspace [0150] 9 [WO.sub.3F.sub.2].sup.4− octahedron or [WO.sub.2/2(O.sub.2F.sub.2)].sup.2− octahedron [0151] 10 radiation-emitting component [0152] 11 semiconductor chip [0153] 12 radiation exit surface [0154] 13 conversion element