Phosphor, Light-Emitting Device Containing a Phosphor and Method for Producing a Phosphor

Abstract

A phosphor is described. In an embodiment a phosphor includes the material Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+), wherein 0<x, y, z<1. Furthermore, a light-emitting device containing the phosphor and a method for producing the phosphor are also described.

Claims

1-16. (canceled)

17. A phosphor comprising: Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+), wherein 0<x, y, z<1.

18. The phosphor according to claim 17, wherein the phosphor consists of Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+), wherein 0<x, y, z<1.

19. The phosphor according to claim 17, wherein 0<y<0.016.

20. The phosphor according to claim 17, wherein 0.005y0.010.

21. The phosphor according to claim 17, wherein 0<x0.10.

22. The phosphor according to claim 17, wherein 0.02<x0.08.

23. The phosphor according to claim 17, wherein 0<z0.050.

24. The phosphor according to claim 17, wherein x=0.04, y=0.008 and z=0.025.

25. The phosphor according to claim 17, wherein the phosphor is a single phase material.

26. A light-emitting device comprising: a light-emitting semiconductor layer sequence comprising an active region for generating light; and a luminescence conversion element containing a phosphor according to claim 17.

27. The light-emitting device according to claim 26, wherein the luminescence conversion element is arranged as at least one layer or platelet in a beam path of a light generated by the light-emitting semiconductor layer sequence.

28. The light-emitting device according to claim 26, wherein the luminescence conversion element further comprises Y.sub.3Al.sub.5O.sub.12:Ce.

29. A method for producing a phosphor according to claim 17, wherein Al(OH).sub.3, CaCO.sub.3, Mg(OH).sub.2.4MgCO.sub.3.6H.sub.2O, MnO.sub.2 and GeO.sub.2 are provided as raw materials and the raw materials are heated together at a temperature of at least 1500 C.

30. The method according to claim 29, wherein the temperature is at least 1550 C.

31. The method according to claim 29, wherein the temperature is at least 1600 C.

32. The method according to claim 29, wherein the raw materials are provided as mixed powder before heating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Further features, advantages and expediencies will become apparent from the following description of exemplary embodiments in conjunction with the figures.

[0026] FIG. 1 shows schematic views of method steps of a method for producing a phosphor according to an embodiment.

[0027] FIGS. 2 to 4 show experimental results of phosphor samples according to further embodiments.

[0028] FIG. 5 shows a schematic view of light-emitting device with a phosphor according to a further embodiment.

[0029] Components that are identical, of identical type and/or act identically are provided with identical reference symbols in the figures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0030] In FIG. 1, an embodiment of a method for producing a phosphor comprising Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+) with 0<x, y, z<1 is shown.

[0031] In a first method step 11, high purity Al(OH).sub.3, CaCO.sub.3, Mg(OH).sub.2.4MgCO.sub.3.6H.sub.2O, MnO.sub.2 and GeO.sub.2 are provided as raw materials. The raw materials are weighted and provided in respective amounts according to their respective fractions in the finished phosphor.

[0032] In a further method step 12, the raw materials are formed to a powder by milling in a crucible such as, for example, an agate crucible. In order to provide a well-mixed powder of the raw materials, the milling can be performed, for example, for more than 30 minutes.

[0033] Afterwards, the mixed powder of the raw materials is moved into a heat-resistant crucible such as, for example, an Al.sub.2O.sub.3 crucible and put into a furnace so that, in a further method step 13, the raw materials are heated to a target temperature of equal to or more than 1500 C., preferably of equal to or more than 1550 C. and particularly preferably of equal to or more than 1600 C. When the heating temperature reaches the target temperature, the temperature is kept stable and the mixed powder is fired for a sufficiently long time, for example for about 4 hours, during which, as a final product, the phosphor is formed.

[0034] In a further method step 14, which may also be omitted, the product can be milled to form a phosphor powder.

[0035] The phosphor produced by the described method comprises and preferably consists of the material Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+) with 0<x, y, z<1. Depending on the provided relative amounts of the raw materials, the parameters x, y and z preferably lie in the following ranges: [0036] 0<x0.10 or 0.01x0.08 or 0.02x0.06 or 0.03x0.05 or x=0.04; [0037] 0<y<0.016 or 0.001y0.015 or 0.002y0.012 or 0.004y0.012 or 0.005y0.010 or 0.007y0.009 or y=0.008. [0038] 0<z0.050 or 0.010z0.040 or 0.015z0.035 or 0.020z0.030 or z=0.025.

[0039] FIGS. 2 to 4 show experimental measurements of phosphor samples comprising the material Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+) and being produced by the method described before, wherein various manufacturing parameters were varied.

[0040] In FIG. 2, x-ray diffraction (XRD) measurements 21, 22 and 23 of different samples of phosphors with the material Ca(Al.sub.11.927Mg.sub.0.04Ge.sub.0.008)O.sub.19:(0.025Mn.sup.4+), i.e., with the parameters x=0.04, y=0.008 and z=0.025, are shown, wherein the different samples were produced at different firing temperatures. For comparison, the JCPDS (Joint Committee on Powder Diffraction Standards) standard for CaAl.sub.12O.sub.19 (38-04790) is also shown and marked with reference numeral 24. The measurements 21, 22 and 23 belong to powder samples, which were fired for 4 hours at temperatures of 1500 C., 1550 C. and 1600 C., respectively.

[0041] In the measurement 21 of the phosphor sample fired at a target temperature of 1500 C., Al.sub.2O.sub.3 diffraction peaks, which are marked with the asterisks (*), can be identified, which suggest the presence of a second phase formed by Al.sub.2O.sub.3. While the Al.sub.2O.sub.3 second phase peaks are already smaller in the measurement 22 of the phosphor sample fired at a target temperature of 1550 C., no indication of a second phase can be found in measurement 23 of the phosphor sample fired at a target temperature of 1600 C., which indicates that the phosphor was produced in a single, i.e., pure, phase.

[0042] FIG. 3 shows measurements 31, 32, 33 of the respective emission intensity I (in arbitrary units) of several phosphor samples with the material Ca(Al.sub.11.927Mg.sub.0.04Ge.sub.0.008)O.sub.19:0.025Mn.sup.4+, wherein the different samples were again produced at different firing temperatures. As described for the measurements shown in FIG. 2, the measurements 31,32, 33 belong to powder samples, which were fired for 4 hours at temperatures of 1500 C., 1550 C. and 1600 C., respectively. The excitation wavelength was 460 nm.

[0043] The highest luminescent intensity was reached for the sample fired at a temperature of 1600 C. Thus, the higher phase purity of the sample belonging to the measurement 33 leads to a higher performance.

[0044] As the conversion performance of a phosphor increases with increasing purity, a firing temperature of 1600 C. and a heating time of 4 hours were chosen for the measurement shown in FIG. 4 for producing the examined phosphor samples.

[0045] FIG. 3 shows measurements which are the results of the emission intensity I (in arbitrary units) of several phosphor samples with different Ge concentrations x, shown on the horizontal axis. In particular, phosphor samples were produced with the material Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:zMn.sup.4+ with x=0.04 and z=0.025, whereas the Ge concentration y was chosen to be 0.005, 0.008, 0.010 and 0.015. For comparison, a Ge-free phosphor sample, i.e., a phosphor with y=0, was also investigated. It can be seen that for a Ge concentration of 0.005, the emission intensity of the phosphor increases by about 25%. Furthermore, for x=0.008 When y=0.005, the relative emission intensity of the phosphor increases dramatically by a factor of more than 2.2. On the other hand, the emission intensity of the phosphor sample with a Ge concentration of about 0.016 is nearly the same as the emission intensity of the Ge-free sample, whereas for a Ge concentration of 0.010 the relative emission intensity is about the same as for a Ge concentration of 0.005. The quantum efficiency of the best sample was measured to be as high as 46%. This value is, for example, higher than the quantum efficiency of about 45% of commercially available fluoride-based phosphors with the material 3.5MgO.0.5MgF2.GeO.sub.2 doped with Mn.sup.4+, measured under similar conditions, so that the phosphor described herein can be used to replace the commercially available phosphor. Moreover, the phosphor described herein is much less cost-intensive than the commercially available phosphor.

[0046] The measurements shown in FIGS. 2 to 4 clearly show that, in particular, by the introduction of Ge atoms in the crystal lattice of the phosphor described herein and by choosing suitable manufacturing conditions the phosphor performance can be significantly increased compared to phosphors known in the art. Furthermore, the introduction of Ge into the crystal lattice does not change the solid state phase compared to an unmodified CaAl.sub.12O.sub.19:Mn.sup.4+ phosphor, which indicates that the phosphor described herein is a solid solution. A comparison of the excitation spectrum and the emission spectrum of the phosphor described herein with the respective spectra of an unmodified CaAl.sub.12O.sub.19:Mn.sup.4+ phosphor shows that neither spectrum changes with regard to the relative intensities and positions of the peaks due to the addition of Ge into the crystal lattice, so that there is no blue or red shift of the spectra. Hence, the spectral properties of the herein-described phosphor are independent of the disclosed Ge concentrations and the phosphor described herein can still be excited by blue light and can emit light in the deep red spectral region, whereas the conversion performance of the phosphor can be increased depending on the Ge concentration. Moreover, the manufacturing method is quite simple, as neither high pressure nor a special atmosphere is needed.

[0047] In FIG. 5, a light-emitting device 1 is shown according to a further embodiment. The light-emitting device 1 comprises a light-emitting semiconductor layer sequence 2 and a luminescence conversion element 3 containing a herein-described phosphor with the material Ca(Al.sub.12-x-y-zMg.sub.xGe.sub.y)O.sub.19:(zMn.sup.4+) with 0<x, y, z<1. In particular, the luminescence conversion element 3 can comprise a phosphor, as discussed in connection with the foregoing figures and embodiments.

[0048] The light-emitting semiconductor layer sequence 2 has an active region 4 for generating light and can, for example, be embodied as a light-emitting semiconductor chip with an epitaxially grown semiconductor layer sequence. In particular, the light-emitting device 1 can be embodied as a light-emitting diode with the herein-described phosphor.

[0049] The light-emitting semiconductor layer sequence 2 is based on the III-V compound semiconductor material system In.sub.xAl.sub.yGa.sub.1-x-yN with 0x1, 0y1 and x+y1 and is embodied to emit ultraviolet to green light. In particular, the light-emitting semiconductor layer sequence 2 can be embodied to emit blue light, for example with a wavelength of about 460 nm.

[0050] The light-emitting semiconductor layer sequence can furthermore comprise a substrate 5, on which semiconductor layers are deposited. The substrate 5 can, for example, comprise an electrically insulating material or a semiconductor material, for instance a compound semiconductor material system as mentioned above. For example, the substrate can comprise sapphire, GaAs, GaP, GaN, InP, SiC, Si and/or Ge or be composed of such a material.

[0051] The semiconductor layer sequence 2 can have as active region 4 a layer or a layer stack forming a conventional pn junction, a double heterostructure, a single quantum well structure (SQW structure) or a multiple quantum well structure (MQW structure). Furthermore, the semiconductor layer sequence 2 can comprise further undoped, n-doped and p-doped semiconductor layers, of which layers 6 and 7 are shown purely exemplarily, as well as electrodes, passivation layers and optical layers, for example, which are not discussed in detail, since the general structure of a light-emitting semiconductor layer sequence is known to a person skilled in the art.

[0052] In the embodiment shown in FIG. 5, the luminescence conversion element 3 is formed as a layer or platelet, which comprises or consists of the herein described phosphor and which is arranged in a beam path of the light generated by the light-emitting semiconductor layer sequence 2. In particular, the layer- or platelet-shaped luminescence conversion element 3 is directly deposited on the light-emitting semiconductor layer sequence 2. For example, the luminescence conversion element 3 is arranged as a layer or platelet containing the phosphor as powder in a matrix material, wherein the matrix material can be a plastic material or a ceramic material. Alternatively, the phosphor itself can, for example, be a solid or powder-like layer or platelet. Furthermore, the luminescence conversion element 3 can be formed as a casting enclosing the light-emitting semiconductor layer sequence 2, wherein in this case the luminescence conversion element 3 preferably comprises a plastic matrix material containing a phosphor powder. The luminescence conversion element 3 can also be remote from the light-emitting semiconductor layer sequence 2.

[0053] Furthermore, the luminescence conversion element 3 can comprise an additional phosphor that, for example, converts light produced by the light-emitting semiconductor layer sequence 2 to light in a green to yellow spectral region. In particular, the additional phosphor can comprise Y.sub.3Al.sub.5O.sub.12:Ce (YAG:Ce). A combination of the herein-described red emitting phosphor, a green to yellow emitting additional phosphor such as, for example, YAG:Ce and a blue light-emitting semiconductor layer sequence can be very suitable for producing warm-white light. The additional phosphor can be contained in an additional luminescence conversion element or can be contained together with the herein-described phosphor in the luminescence conversion element 3.

[0054] Alternatively or additionally to the features described in connection with the figures, the embodiments shown in the figures can comprise further features described in the general part of the description. Moreover, features and embodiments of the figures can be combined with each other, even if such a combination is not explicitly described.

[0055] The invention is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises 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 exemplary embodiments.