DE102016116016A1 - Phosphor, use of a phosphor, and method of making a phosphor - Google Patents

Abstract

The invention relates to a phosphor (1) of the formula (REaCa1-a-bCeb) 3 (Mg1-cAlc) 2 (AldSi1-d) 3O12, where RE is at least one element of the rare earths, 0 ≤ a ≤ 1, b> 0 , a + b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 1, and c + d> 0 where the phosphor is a cubic crystal system having the space group

Description

The invention relates to a phosphor. Furthermore, the invention relates to the use of a phosphor. Furthermore, the invention relates to a method for producing a phosphor.

In optoelectronic components, such as light emitting diodes (LEDs), phosphors are used, which are set up for wavelength conversion. Particularly interesting are red emitting phosphors. Almost all hitherto existing red emitting phosphors are based on europium or manganese as phosphor centers, for example (Sr, Ca, Ba) ₂ AlSiN ₃ : Eu, (Sr, Ca) AlSiN ₃ : Eu or K ₂ SiF ₆ : Mn. However, these phosphors have the disadvantage that they have a very long cooldown. Long cooldowns mean that after their excitation into an excited state, the phosphors only slowly return to the ground state with the emission of red radiation. This results in a high excitation power to a rapid saturation of the phosphor centers and quenching effects that reduce the efficiency of the phosphors. In comparison to europium- or manganese-doped phosphors, cerium-doped phosphors have comparatively short cooldowns. This results in a significantly slower saturation of the phosphor centers and a significantly higher efficiency of cerium-doped phosphors with high excitation power. This is particularly interesting for applications in the high-power range, ie for applications with a power density from 1 watt per square millimeter. However, there are only very few cerium-doped red-emitting phosphors so far.

To the knowledge of the inventors, only a few cerium-doped red solid-state phosphors are known in the literature. A phosphor of the formula Lu ₂ CaMg ₂ (Si, Ge) ₃ O ₁₂ : Ce which emits light at an emission maximum of 605 nm is known ( Setlur, AA et al., Chem. Mater. 2006, 18, 3314-3322 ; US 7,094,362 B2 ). Also known is a red-emitting phosphor of the formula Sr ₆ (Y _{1 -x} Ce _x ) ₂ Al ₄ O ₁₅ (0.1 ≦ x ≦ 0.2) having a maximum of the emission radiation of about 600 nm ( Kawano Y. et al., Optical Materials Express 2014, 4, 1770 ). Another known red emitting phosphor follows the formula CaSiN ₂ : Ce and has an emission maximum of about 625 nm ( R. Le Toquin et al., Chemical Physics Letters 2006, 423, 352-356 ).

An object of the invention is to provide a phosphor which has an efficient emission and with which high CRI values can be achieved in a conversion solution. Another object is to provide a simple method for producing a phosphor and its use for wavelength conversion.

These objects are achieved by a phosphor having the features of claim 1, by a method for producing a phosphor having the features of claim 15 and by the use claims 13 and 14. Advantageous embodiments and developments of the invention are the subject of the dependent claims.

In at least one embodiment, the phosphor has the formula (RE _a Ca ₁ -ab Ce _b ) ₃ (Mg _{1 -c} Al _c ) ₂ (Al _d Si _1-d ) ₃ O ₁₂ . In this case, RE is at least one element of the rare earths, 0 ≦ a ≦ 1, b> 0, a + b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 1 and c + d> 0. The phosphor has a cubic crystal system with the room group Ia 3 d on.

Phosphor here and hereafter designates a wavelength conversion substance, that is to say a material which is set up for the absorption and emission of electromagnetic radiation. In particular, the phosphor absorbs radiation having a smaller wavelength maximum than the emission maximum and emits radiation with an emission maximum shifted in the red direction.

In accordance with at least one embodiment, the phosphor emits radiation from the red spectral range of the electromagnetic spectrum. Alternatively or additionally, RE can be yttrium (Y), lutetium (Lu), gadolinium (Gd) and / or terbium (Tb, where 0 <a <1, a + b <1, 0 <c <1, 0 < d <1 and c + d> 0. In this case, radiation from the red spectral range means radiation with a dominant wavelength of greater than 575 nm.

The inventors have recognized that a red emitting wave conversion substance can be provided by a phosphor having the formula (RE _a Ca ₁ -ab Ce _b ) ₃ (Mg _1-c Al _c ) ₂ (Al _d Si _1-d ) ₃ O ₁₂ , which is a cubic crystal lattice with the space group Ia 3 d and shorter wavelength radiation efficiently converted to the red spectral range.

It is possible that the phosphor has other elements, for example in the form of impurities, these impurities taken together preferably having at most one part by weight in the phosphor of at most 0.1 ‰ or 10 ppm.

According to at least one embodiment, RE is at least one element of the rare earths. Preferably, RE comprises two or more than two rare earths. Preferably, RE is yttrium, lutetium, gadolinium and / or terbium. Particularly preferred is RE Y and / or Lu.

In accordance with at least one embodiment, 0 ≤ a ≤ 1. a denotes the proportion of RE to which the lattice sites of the calcium have been replaced by RE. Preferably, a is greater than 0 and less than 1, in particular between greater than 0.33 and less than 1, for example 0.64 or 0.6667.

According to at least one embodiment, the phosphor has cerium. The proportion of cerium to which the lattice sites of calcium are replaced is symbolized by b. b is greater than 0. In other words, the phosphor described here is necessarily cerium-doped or has cerium. Preferably, b is between 0.001 and 0.3, for example 0.05.

Cer acts here as an activator or dopant. Alternatively or additionally, RE can also act as activator or dopant. The activator can install itself in the crystal lattice. In substitution of divalent elements by trivalent elements, for example, cerium ³⁺ charge neutrality is not given. Therefore, a charge compensation is usually necessary. The charge compensation can be done in particular by the ratio of the other elements. Preferably, cerium is present in the oxidation state +3.

By doping the phosphor with cerium, it has a short cooldown. Thus, it is possible to excite this phosphor with a radiation source, without causing rapid saturation of the phosphor centers and the associated quenching losses. With the phosphor can therefore achieve high luminance. For example, the decay times of manganese-doped phosphors or europium-doped phosphors are by comparison up to six orders of magnitude slower.

In accordance with at least one embodiment, the phosphor comprises calcium. This is especially the case when the sum of the proportions of RE and cerium is less than 1.

According to at least one embodiment, the phosphor has magnesium. Preferably, MgO ₆ octahedra are present in the phosphor. The lattice sites of magnesium may be partially replaced by aluminum. In particular, the proportion of aluminum at the lattice sites of magnesium, denoted here as c, is ≥ 0 and ≤ 1. Preferably, c has a value between 0 and 1. In other words, the lattice sites of magnesium may be at least partially replaced by aluminum.

In accordance with at least one embodiment, the phosphor has SiO ₄ tetrahedra. Preferably, the silicon lattice sites are at least partially replaced by aluminum. The proportion of aluminum at the silicon lattice sites is here designated by a d and is preferably ≥ 0 and ≦ 1. In particular, d has a value of greater than 0 and less than 1. In other words, the lattice sites of the silicon may be at least partially replaced by aluminum.

In accordance with at least one embodiment, the phosphor comprises MgO ₆ octahedra and SiO ₄ tetrahedra, wherein at least either the lattice sites of the magnesium or the lattice sites of the silicon are partially replaced by aluminum or both. The (Al, Mg) O ₆ octahedra and (Si, Al) O ₄ tetrahedra are linked by their vertices to form a framework of alternating tetrahedra and octahedra. The rare earth and calcium atoms are located in cuboctahedron spanned by this framework.

In accordance with at least one embodiment, the phosphor comprises a cubic crystal system. The cubic crystal system has all the space groups which each have a threefold rotational or Drehinversionsachse in four different directions. Preferably, the phosphor has the space group Ia 3 d on. The designation of the space group of the crystal system is sufficiently known to the person skilled in the art and is therefore not explained in detail here.

In accordance with at least one embodiment, the phosphor has the following empirical formula: (Y _0.33 Lu _0.31 Ca _0.33 Ce _0.02 ) ₃ (Mg _0.75 Al _0.25 ) ₂ (Al _0.166666 Si _{0, 8333} ) ₃ O ₁₂ or (YLu _0.94 CaCe _0.06 ) (Mg _1.5 Al _0.5 ) (Al _0.5 Si _2.5 ) O _12.

In accordance with at least one embodiment, 0.3 <a <1, 0 <b <0.1, 0 <c <0.5 and 0 <d <0.333.

In at least one embodiment, a = 0.64, b = 0.02, c = 0.25 and d = 0.1667.

The parameters a, b, c and / or d can each have a tolerance of 10%, 5%, 3% or 1% of the values described above.

In accordance with at least one embodiment, the lattice constant a of the cubic crystal system of the phosphor is between 11.8 angstroms and 12.3 angstroms, preferably between 11.9 angstroms and 12.1 angstroms.

According to at least one embodiment, c = 0. The result is the structural formula (RE _a Ca _1-ab Ce _b ) ₃ Mg ₂ (Al _d Si _1-d ) ₃ O ₁₂ . For RE, a, b and d the above statements apply.

According to at least one embodiment, d = 0. The result is the structural formula (RE _a Ca _1-from Ce _b ) ₃ (Mg _1-c Al _c ) ₂ Si ₃ O ₁₂ . For RE, a, b and c the above statements apply.

In accordance with at least one embodiment, a = 0. The structural formula (Ca _{1 -b} Ce _b ) ₃ (Mg _{1 -c} Al _c ) ₂ (Al _d Si _1-d ) ₃ -O ₁₂ results. For RE, b, c and d the above statements apply.

In accordance with at least one embodiment, a = 0 and d = 0. The structural formula (Ca _{1 -b} Ce _b ) ₃ (Mg _{1 -c} Al _c ) ₂ Si ₃ O ₁₂ results. For RE, b and c the above statements apply.

In accordance with at least one embodiment, the phosphor has a dominant wavelength of greater than 575 nm, preferably greater than 580 nm. The dominant wavelength is the monochromatic wavelength which produces the same color impression as a polychromatic light source. The dominant wavelength is the wavelength perceived by the human eye. In general, the dominant wavelength deviates from a maximum intensity wavelength. In particular, the dominant wavelength in the red spectral range is at smaller wavelengths than the wavelength of maximum intensity.

According to at least one embodiment, the centroid wavelength is greater than 600 nm with a half-width greater than 125 nm. The centroid wavelength, also referred to as centroid wavelength, denotes the wavelength at which a given spectrum is integrally divided into two equal parts.

The phosphor described herein preferably exhibits a broad emission band with a dominant wavelength greater than 575 nm and a centroid wavelength greater than 600 nm with a half-width greater than 125 nm.

In accordance with at least one embodiment, the phosphor absorbs radiation from the blue to green wavelength range. The phosphor has an absorption maximum between 450 and 470 nm in the range of 400 nm and 550 nm. The phosphor can have broad absorption bands around the wavelengths of the absorption maxima at 310 nm and 460 nm. In particular, the broad absorption behavior at around 460 nm is optimal for the application of this phosphor in conversion LEDs.

In accordance with at least one embodiment, the phosphor has a Stokes shift of at least 150 nm. This is surprising in comparison to the previously known cerium-activated phosphors with a garnet structure. The Stokes shift was determined by the difference between the absorption maximum (reflection minimum in the blue spectral range) and the centroid wavelength. The Stokes shift is defined here as the wavelength difference between the wavelength of the absorption maximum and the peak of the highest emission peak. For broad emissions consisting of several single emission bands, the spectral intensity distributions of the individual bands are described by Gaussian functions. For the calculation of the Stokes shift, the single energy emission band with the highest energy (which corresponds to the smallest emission wavelength) determined in this way is used here. The determination takes place partly differently in the literature, for example based on wavelength distribution functions or energy distribution functions, which leads to respectively different values. The method used here was chosen because it is easier to understand.

The invention further relates to the use of the phosphor as a wavelength conversion substance. The phosphor described here is preferably used as the wavelength conversion substance in an optoelectronic component.

In accordance with at least one embodiment, the optoelectronic component is a light-emitting diode. Under construction element here not only finished components are understood, such as light emitting diodes or laser diodes, but also substrates and semiconductor layers, so that, for example, already represent a composite of a copper layer and a semiconductor layer, a component and form part of a parent second component, in which, for example additional electrical connections are available. The optoelectronic component is preferably a thin-film semiconductor chip, in particular a thin-film light-emitting diode chip.

In accordance with at least one embodiment, the optoelectronic component comprises a layer sequence. The layer sequence may be a sequence of a p-doped and an n-doped semiconductor layer, wherein the layers are arranged one above the other. The layer sequence can emit electromagnetic radiation, preferably electromagnetic radiation from the blue to green spectral range, which can be absorbed by the phosphor.

According to at least one embodiment, the layer sequence may be a semiconductor layer sequence of a semiconductor chip. The semiconductor layer sequence of the semiconductor chip is preferably based on a III-V compound semiconductor material. The semiconductor material is preferably a nitride compound semiconductor material such as Al _n In _{1 nm} Ga _m N or else a phosphide compound semiconductor material such as Al _n In _{1 nm} Ga _m P, where 0 ≦ n ≦ 1, 0 ≦ m ≤ 1 and n + m ≤ 1. Likewise, the semiconductor material may be Al _x Ga _1-x As with 0 ≤ x ≤ 1. In this case, the semiconductor layer sequence may comprise dopants and additional constituents. For the sake of simplicity, however, only the essential constituents of the crystal lattice of the semiconductor layer sequence, that is to say Al, As, Ga, In, N or P, are indicated, even if these may be partially replaced and / or supplemented by small amounts of further substances.

According to at least one embodiment, during operation of the optoelectronic component, electromagnetic radiation is emitted by the semiconductor layer sequence and impinges on the phosphor which is arranged in the beam path of the radiation emitted by the semiconductor chip. The radiation is absorbed by the phosphor, which in turn emits radiation, usually with a longer wavelength. Preferably, the phosphor emits radiation from the red wavelength range and the semiconductor chip radiation from the blue wavelength range, so that at partial conversion mixed radiation and at full conversion exits the radiation emitted by the phosphor radiation from the device.

Preferably, the optoelectronic component may have, in addition to the phosphor according to the invention, a further phosphor, for example a garnet, a nitride and / or orthosilicate.

In accordance with at least one embodiment, the phosphor can be embedded in a matrix material. Preferably, the phosphor is embedded embedded in a matrix material as a potting layer or film. The potting may for example be cohesively or a potting compound with a layer sequence connected to an active area. The potting compound may be, for example, a polymer material. In particular, it may be epoxy or silicone, such as a methyl-substituted silicone, for example polydimethylsiloxane and / or polymethylvinylsiloxane, a cyclohexyl-substituted silicone, eg. Polydicylohexylsiloxane or a combination thereof.

In accordance with at least one embodiment, the matrix material may comprise further fillers, for example metal oxides, such as titanium dioxide, silicon dioxide, zirconium dioxide, zinc oxide, aluminum oxide and / or glass particles. Preferably, these fillers are formed as scattering particles.

In accordance with at least one embodiment, the phosphor can be formed as a particle or ceramic plate and at least partially scatter the radiation emitted by the semiconductor chip. The phosphor can simultaneously be used as a luminous center, which partially absorbs the radiation of the radiation emitted by the semiconductor chip and emits a further radiation and is designed as a scattering center for the radiation emitted by the semiconductor chip. The scattering properties of the phosphor can lead to improved radiation extraction from the device. The scattering effect can, for example, also lead to an increase in the absorption probability of the radiation emitted by the semiconductor chip in the phosphor, which may necessitate a smaller layer thickness of the layer containing the phosphor.

In accordance with at least one embodiment, the optoelectronic component has an encapsulation. The encapsulation may in particular be a thin-layer encapsulation.

In accordance with at least one embodiment, the phosphor is in direct contact with the radiation source, ie the semiconductor chip. Thus, the conversion of the radiation emitted by the semiconductor chip into the radiation emitted by the phosphor at least partially close to the radiation source, for example at a distance phosphor and radiation source of less than or equal 200 microns, preferably less than or equal to 50 microns done (so-called chip level conversion) ,

In accordance with at least one embodiment, the phosphor is spaced from the radiation source. Thus, at least in part, the conversion of the radiation emitted by the semiconductor chip into the radiation converted by the phosphor can take place at a large distance from the radiation source, for example at a distance between phosphor and radiation source of greater than or equal to 200 μm, preferably greater than or equal to 750 μm preferably greater than or equal to 900 microns (so-called Remote Phosphor Conversion).

In accordance with at least one embodiment, the phosphor is used in high power white LEDs. For white light sources or full conversion in high power applications, it is necessary that the phosphors used produce high luminance densities of converted radiation at high power densities of the stimulating blue to green primary radiation. Europium- or manganese-doped phosphors are not capable of this. The inventors have now recognized that high luminance densities of converted radiation can be generated by the use of the cerium-doped phosphors described here at high power densities of the exciting primary radiation.

In accordance with at least one embodiment, the phosphor is used in a laser active remote phosphor application (LARP). LARP is well known to those skilled in the art and therefore will not be discussed further here.

In accordance with at least one embodiment, the phosphor has a Stokes shift of at least 150 nm.

In comparison to common phosphors such as the YAG: Ce phosphor, this phosphor described here has a high red shift and a high Stokes shift. The red shift represents a significant advantage over z. Example, yellow-green emitting garnet phosphors such as Y ₃ Al ₅ O ₁₂ or Lu ₃ Al ₅ O ₁₂ is. The high Stokes shift is compared to all garnet phosphors with high red shift advantage, such as CaLu ₂ Mg ₂ Si ₃ O ₁₂ . The phosphor according to the invention is the only phosphor known to the inventors, which combines both of these advantages. The inventors have recognized that by using the cerium doped phosphor described herein as the wavelength conversion material, a more efficient device can be provided compared to other red emitting devices having similar Stokes shift phosphors, such as europium or manganese doped phosphors, because of quenching problems and other problems resulting from optical saturation are reduced.

The phosphor described here has some advantages compared to, for example, the comparative example CaLu ₂ Mg ₂ Si ₃ O ₁₂ . Compared to the comparative example, the phosphor described here exhibits a high Stokes shift. The main difference to the comparative example is the addition of aluminum. The inventors have recognized that the introduction of aluminum into the lattice sites of silicon or magnesium can increase the Stokes shift. Previously known aluminum-containing garnet phosphors have a lower Stokes shift. The phosphor described herein exhibits a high Stokes shift of greater than 150 nm. Second, the phosphor described herein exhibits high absorption efficiency at 460 nm compared to the comparative example, which has an absorption maximum at about 475 nm. In optoelectronic components which emit preferably in the blue spectral range, especially in the wavelength range from 440 to 460 nm, an optimal excitation of this phosphor can be achieved by the use of the phosphor described here. Compared to the comparative example, therefore, more of the radiation emitted by the semiconductor chip is absorbed by the phosphor described here. This results in a higher efficiency compared to the comparative example.

The invention further relates to a method for producing a phosphor. Preferably, the method described here produces the phosphor described above. All designs for the phosphor also apply to the process and vice versa.

• A) Vermengen der Ausgangsstoffe aus Vorläuferverbindungen z. B., aber nicht ausschließlich Carbonaten, Oxalaten, Oxiden, Hydroxiden oder Nitraten der in der Formel genannten Elemente,
• B) Aufheizen des unter A) erhaltenen Gemenges auf eine Temperatur von über 1200 °C,
• C) Glühen des Gemenges bei einer Temperatur von über 1200 °C unter reduzierender Atmosphäre,
• D) Abkühlen des Gemenges.

In accordance with at least one embodiment, the method for producing a phosphor having the formula (RE _a Ca ₁ -ab Ce _b ) ₃ (Mg _1-c Al _c ) ₂ (Al _d Si _1-d ) ₃ O ₁₂ , wherein RE at least one Rare earth element, 0 ≦ a ≦ 1, b> 0, a + b ≦ 1, 0 ≦ c ≦ 1, 0 ≦ d ≦ 1, and c + d> 0, the steps are as follows:

• A) mixing the starting materials from precursor compounds z. But not exclusively carbonates, oxalates, oxides, hydroxides or nitrates of the elements mentioned in the formula,
• B) heating the mixture obtained under A) to a temperature of more than 1200 ° C.,
• C) annealing the mixture at a temperature of over 1200 ° C. under a reducing atmosphere,
• D) cooling the batch.

According to at least one embodiment, the proportion of the starting materials based on the total amount of the mixture has the following compositions:
RE ₂ O ₃ between 46% and 48% inclusive, Al ₂ O ₃ between 7% and 9% inclusive, SiO ₂ between 23% inclusive and 25% inclusive, MgO between 8% inclusive and 10% inclusive, CeO ₂ intermediate including 0.8% and 1.8% inclusive, CaO between 8% inclusive and 10% inclusive, and the total is 100% total.

According to at least one embodiment, RE ₂ O _3, a mixture of Y ₂ O ₃ and Lu ₂ O _3, wherein the proportion of Y ₂ O ₃ is between 14% and including 16% and the proportion of Lu ₂ O ₃ is between 31% and including 33%.

In accordance with at least one embodiment, the process is carried out as a solid-state reaction or sol-gel process.

The inventors have found that by mixing the starting substances with the corresponding portions of the elements, it is possible to provide a phosphor which emits red and has high efficiency and emission stability. In particular, oxides such as RE ₂ O ₃ , CeO ₂ , MgO, CaO, SiO ₂ , carbonates such as MgCO 3, hydroxides such as Ca (OH) ₂ or nitrates such as RE (NO ₃ ) _{3 are} mixed as starting materials. The starting materials described here are examples and are not intended to be limiting. Subsequently, the starting materials can be annealed. The annealing can take place at a temperature greater than 1200 ° C. Preferably, the annealing in step C is carried out at a temperature between 1200 ° C to 2000 ° C inclusive. Preferably, the annealing is performed at a temperature of or above 1300 ° C.

The annealing can be carried out under a reducing atmosphere. Under reducing atmosphere, for example, an inert or a reducing atmosphere can be understood. A reducing atmosphere does not exclude oxygen being present in this reducing atmosphere. For example, the reducing atmosphere may be a nitrogen or inert gas atmosphere, such as an argon atmosphere.

In accordance with at least one embodiment, method step C may be performed at least once. In particular, the annealing can also be carried out one to five times, in particular one to three times, for example twice. Multiple annealing of the starting materials with or without intermediate post-processing such. As grinding and / or sieving can further improve the crystallinity or grain size distribution of the phosphor. Further advantages may be a lower defect density associated with improved optical properties of the resulting phosphor and / or higher stability of the resulting phosphor.

Occasionally, according to one embodiment, short annealing steps may also be performed in air at low temperature, for example less than 600 ° C. The annealing can be carried out in a crucible, for example, tungsten, corundum, platinum or graphite. In this case, the crucible may have a lining, for example of molybdenum or a lining of sapphire. The annealing can in a gas-tight furnace under reducing atmosphere and / or inert gas such. B. in hydrogen, ammonia, argon, nitrogen or mixtures thereof. The atmosphere can be fluid or stationary. It may also be advantageous for the quality of the resulting phosphor when elemental carbon is present in finely divided form in the furnace space. Alternatively, it is possible to add carbon directly into the mixture of starting materials.

In accordance with at least one embodiment, the method steps A to D described here take place in the order mentioned here.

After annealing, the phosphor can be cooled. Subsequently, the phosphor can be subjected to a post-treatment. The isolation of the phosphor can be carried out by washing in brine and / or by acid. The acid may be selected, for example, from a group comprising hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, organic acids and mixtures thereof. The liquor may be selected from a group comprising potassium hydroxide, caustic soda and mixtures thereof. Such washes can increase the efficiency when producing a phosphor. Furthermore, this can be used to remove secondary phases, glass phases or other impurities, as well as to improve the optical properties of the phosphor. The phosphor may be subjected to further fractionation and classification steps such as sieving, flotation or sedimentation.

In accordance with at least one embodiment, a flux or flux is added to the process. The flux may be, for example, boric acid, alkaline earth borates or fluorides such as cryolites. The fluxes can improve crystal growth.

In accordance with at least one embodiment, the preparation takes place as a solid-state reaction. The starting substances are weighed in and mixed. The mixing can be done for example with a ball mill, an asymmetric centrifuge or with a tumble mixer. The mixture may be transferred to a crucible, for example of alumina or platinum, and then heated at a temperature greater than 1200 ° C. The exact temperature depends on the starting materials. The heating can be carried out for several hours under reducing atmosphere. The product can optionally be ground afterwards. The heating and annealing steps can be repeated as desired to improve the phosphor quality.

Alternatively, the phosphor can also be prepared by sol-gel method. The appropriate starting materials are weighed and dissolved in an acidic environment, such as citric acid or nitric acid. The sol-gel process can be carried out in various steps, such as in Yan et al, Trans Nonferrus Met Soc China 2008, 648-653 ; Hemmer, Saarland University, 2009 ; Katelnikovas, Vilnius, Münster 2002 ; Ogieglo, University of Utrecht, 2012 is described. The disclosure of the syntheses in these documents is hereby incorporated by reference.

To remove the minor phases and to improve the phosphor quality, additional washing steps can be carried out. For example, multiple washes can be made by HCl (1-6 mol / L) for one to 12 hours to elute minor phases such as orthosilicates or silicate apatites. Subsequently, a drying of the phosphor powder can take place.

In accordance with at least one embodiment, the phosphor described herein may be prepared as follows. The starting materials are mixed with the following proportion by weight. starting materials Dimensions Y ₂ O ₂ 7,626 g Al ₂ O ₃ 4,099 g SiO ₂ 12,078 g MgO 4,861 g CeO ₂ 0.830 g Lu ₂ O ₃ 15,998 g CaO 4,509 g

Mixing can be done with an asymmetric centrifuge, for example, three times for 30 seconds at 1600 rpm. Subsequently, milling in a mortar mill for 10 minutes and re-mixing in an asymmetric centrifuge (twice for 30 seconds at 1600 rpm) can be performed. The mixture can then be transferred in a corundum crucible with a cover plate and placed in an oven. The furnace may have a reducing atmosphere of 4 percent hydrogen in nitrogen (4% forming gas, 240 L / min). The mixture can be heated to 1350 C ° and annealed for four hours at this temperature. After the mixture has cooled, the sinter cake can be ground in the mortar grinder and sieved through a 45 μm sieve. The powder can be washed with hydrochloric acid to remove by-products. About 20 g of powder can be stirred in 100 ml of half-concentrated acid for one hour. The undissolved, sedimented phosphor powder can be decanted from the acid. Subsequently, 100 ml of a fresh acid can be added to the phosphor. The phosphor can be mixed with this acid and then settles for example overnight. The acid is decanted off and 100 ml of deionized water are added. The phosphor is mixed with the water and it is waited ten minutes until it sediments. The supernatant can then be decanted off. The phosphor is filtered in vacuo and washed with deionized water. Thereafter, the phosphor is dried at 50 C ° for at least two hours.

Further advantages, advantageous embodiments and developments emerge from the embodiments described below in conjunction with the figures.

It shows:

1A an X-ray diffraction powder diffractogram of a phosphor described herein,

2A the crystal structure of an embodiment,

2 B crystallographic data of a phosphor described herein,

3 the Stokes shift,

4A and 4B each an emission spectrum of embodiments and comparative examples,

5A and 5B Reflectance curves according to an embodiment and a comparative example and

6A and 6B in each case a schematic side view of an optoelectronic component according to an embodiment.

In the exemplary embodiments and figures, identical, identical or identically acting elements can each be provided with the same reference numerals. The illustrated elements and their proportions with each other are not to be regarded as true to scale. Rather, individual elements such. As layers, components, device and areas for better representation and / or for better understanding are exaggerated.

The 1A shows an X-ray powder diffraction pattern of the phosphor (YLuCa _0.94 Ce _0.06 ) (Mg _1.5 Al _0.5 ) (Al _0.5 Si _2.5 ) O ₁₂ , which is referred to here and below as Embodiment 1. The relative intensity I in arbitrary units is also given as a function of the diffraction angle Θ 2Θ using copper K _α1 radiation.

The with the reference numerals I The plotted curve shows a measured X-ray powder diffraction pattern and corresponds to the phosphor of Embodiment 1. The obtained X-ray diffraction powder diffractogram I was analyzed by Rietveld analysis. In the Rietveld method, the crystal structure is varied until the diffractogram calculated therefrom best matches the measured diffractogram. The structure of Y ₃ Al ₅ O _{12 was} used as the basis for the Rietveld process. The with the reference number II provided diagram corresponds to the calculated X-ray powder diffraction pattern for the embodiment 1. The reference numeral III provided diagram shows the difference between the X-ray powder diffraction pattern by the reference numeral I and the calculated diagram with the reference numeral II , As can be seen, the correspondence between the measured X-ray powder diffraction pattern is denoted by the reference numeral I and the calculated diagram with the reference numeral II very high. It will thus be apparent to those skilled in the art that the calculated structure is consistent with the present structure.

The 2A shows the crystal structure of Embodiment 1. The MgO ₆ octahedra and SiO ₄ tetrahedra are shown. The lattice sites of the MgO ₆ octahedral magnesium are partially replaced by aluminum. The lattice sites of the silicon of the SiO ₄ tetrahedra are partially replaced by aluminum. The crystallographic layer marked by a white ball is shared by yttrium, lutetium, calcium and cerium. The crystal structure is cubic. The room group is Ia 3 d ,

The 2 B shows the Rietveld refinement data and the most important crystallographic data of Embodiment 1.

C

Kristallsystem, das kubisch ist (hier als cub abgekürzt).

S

Raumgruppe, L Gitterparameter in Angström,

V

Elementarzellvolumen in Angström³, F Anzahl an Formeleinheiten pro Elementarzelle, R verwendete Röntgenstrahlung, T die Temperatur in Kelvin, R_ex/R_p R erwartet/ R profil, wRp WRprofil. Als Profilfunktionen wurden Pseudo-Voigt-Funktionen und als Untergrundfunktion eine Polynomfunktion verwendet. Ferner zeigt die 2B die kristallographischen Lagen bezeichnet durch die Wykoff-Positionen, hier als W bezeichnet der entsprechenden Atome, die hier mit A bezeichnet sind und ihre Koordinaten in der Elementarzelle. Zusätzlich sind die wichtigsten interatomaren Abstände zwischen den Atomen dargestellt. Die Tabelle listet jeweils den Abstand zwischen einem ersten Atom (A1) und einem zweiten Atom (A2), d bezeichnet den Abstand und N die Anzahl an entsprechenden symmetrieäquivalenten Atomen A2, die sich um A1 im selben Abstand befinden.

This mean in the 2 B abbreviations:

C

Crystal system that is cubic (here abbreviated as cub).

S

Space group, L Grid parameters in Angström,

V

Unit cell volume in angstrom ³ , F number of formula units per unit cell, R used X-radiation, T the temperature in Kelvin, R _ex / R _p R expected / R profile, WR profile WR profile. Pseudo-Voigt functions were used as profile functions and a polynomial function as background function. Furthermore, the shows 2 B the crystallographic positions are denoted by the Wykoff positions, here referred to as W, of the corresponding atoms, here denoted by A, and their coordinates in the unit cell. In addition, the most important interatomic distances between the atoms are shown. The table lists in each case the distance between a first atom (A1) and a second atom (A2), d denotes the distance and N the number of corresponding symmetry-equivalent atoms A2, which are at the same distance around A1.

The 3 shows the Stokes shift Δλ of Comparative Examples V1 to V4 and Embodiment A1. The embodiment A1 corresponds to the embodiment 1 of 1A to 2 B , As comparative examples, Y ₃ Al ₅ O ₁₂ : Ce, Lu ₃ Al ₅ O ₁₂ : Ce, CaLu ₂ Mg ₂ Si ₃ O ₁₂ : Ce, Gd ₃ Al ₄ GaO ₁₂ : Ce were used. The first two comparative examples V1 and V2 are commercially available. Comparative Examples V3 and V4 can be prepared by solid state reaction. In this case, divalent oxides can be used as starting materials, which are heated in an oven and annealed under a reducing atmosphere at a temperature of greater than 1200 C ° for two to eight hours. λ _max here means the main peak of the blue absorption wavelength and λ _cent here means the center of gravity wavelength. From the table of 3 It can be seen that the embodiment A1 has the largest Stokes shift compared to the comparative examples V1 to V4, ie a Stokes shift of greater than 150 nm.

The 4A and 4B each show an emission spectrum according to an embodiment and a comparative example. In each case, the relative intensity I _r in percent as a function of the wavelength λ in nm is shown. The curve with the reference number I is the comparative example Y ₃ Al ₅ O ₁₂ : Ce and the curve by the reference numeral II Embodiment 1 Compared to the conventional YAG phosphor, the phosphor of the present invention exhibits a strong red shift.

The 4B shows the emission spectrum of the embodiment 1. The phosphor was excited here with an excitation wavelength of 460 nm. The wavelength maximum here is greater than 575 nm.

The phosphor described herein is a broad emission band with a dominant wavelength λ _dom of greater than 575 nm and a center wavelength λ _cent greater than 600 nm with a half width of greater than 125 nm. The phosphor exhibits two absorption maxima λ1 and λ2 at about 310 nm and about 460 nm In particular, the phosphor described herein can absorb at around 460 nm, which is ideal for conversion LED applications.

The 5A and 5B show a reflectivity curve of an embodiment and / or a comparative example. The reflectivity R is shown in percent as a function of the wavelength λ in nm. The reference number I shows the comparative example CaLu ₂ Mg ₂ Si ₃ O ₁₂ , the embodiment 1 is denoted by the reference numeral II shown. It can be seen from the reflectivity curves that the reflectivity for embodiment 1 has a minimum at 460 nm and can therefore be used excellently for blue-emitting conversion LEDs. In comparison, the comparative example shows a reflectivity maximum at longer wavelengths at about 475 nm. The optimum range that should be provided for blue emitting LEDs is here the range at a wavelength of 440 nm to 460 nm, which is in 5B is marked by two vertical lines.

The 6A and 6B each show a schematic side view of an optoelectronic component according to an embodiment. The component 100 includes a housing 20 in conjunction with a carrier substrate 15 , The housing may comprise a ceramic or a heat- or radiation-resistant plastic. In a recess 25 of the housing 20 is a semiconductor chip 10 arranged, which emits radiation during operation of the device. Preferably, the semiconductor chip emits 10 Radiation from the blue spectral range. The sides of the recess 25 are beveled here and can be a reflective Include material. The semiconductor chip 10 can have electrically conductive connections 30 . 31 and a bonding wire 32 be energized.

The component 100 has a conversion element 61 on. The conversion element 61 includes the phosphor described herein 60 , The conversion element 61 is directly on the radiation exit surface of the semiconductor chip 10 arranged. In the recess may additionally a casting 50 be introduced. The casting 50 For example, it can be a silicone.

The casting 50 can the case 20 overhang and additionally as a lens 70 be formed.

The optoelectronic component 100 of the 6B is different from the device 100 of the 6A in that here is the phosphor 60 is formed as a particle and within the recess 25 in the potting 50 is embedded. The embedding of the phosphor 60 may be homogeneous or inhomogeneous. Furthermore, the phosphor can 60 also with a concentration gradient in the potting 50 be embedded. The phosphor 60 can also be further processed as a ceramic. The semiconductor chip 10 is in this example with a potting 50 potted, with the casting 50 in turn may optionally have a lens.

The embodiments described in connection with the figures and their features can also be combined with each other according to further embodiments, even if such combinations are not explicitly shown in the figures. Furthermore, the embodiments described in connection with the figures may have additional or alternative features as described in the general part.

The invention is not limited by the description based on the embodiments of these. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

LIST OF REFERENCE NUMBERS

100

 optoelectronic component

10

 Semiconductor chip

15

 carrier substrate

20

 casing

25

 recess

30

 first connection

31

 second connection

32

 bonding wire

50

 grouting

60

 Phosphor particles

61

 conversion element

70

lens

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7094362 B2 [0003]

Cited non-patent literature

• Setlur, AA et al., Chem. Mater. 2006, 18, 3314 to 3322 [0003]
• Kawano Y. et al., Optical Materials Express 2014, 4, 1770 [0003]
• R. Le Toquin et al., Chemical Physics Letters 2006, 423, 352-356 [0003]
• Yan et al, Trans Nonferrus Met Soc. China 2008, 648-653 [0065]
• Hemmer, Saarland University, 2009 [0065]
• Katelnikovas, Vilnius, Münster 2002 [0065]
• Ogieglo, University of Utrecht, 2012 [0065]

Claims (18)

Phosphor ( 1 ) having the formula (RE _a Ca ₁ -ab Ce _b ) ₃ (Mg _{1 -c} Al _c ) ₂ (Al _d Si _1-d ) ₃ O ₁₂ , where RE is at least one element of rare earths, 0 ≤ a ≤ 1 , b> 0, a + b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, and c + d> 0, wherein the phosphor is a cubic crystal system having the space group Ia 3 d having. Phosphor ( 1 ) according to claim 1, adapted to emit radiation from the red spectral region of the electromagnetic spectrum, where RE is Y, Lu, Gd and / or Tb, where: 0 <a <1, a + b <1, 0 < c <1, 0 <d <1 and c + d> 0. Phosphor ( 1 ) according to at least one of the preceding claims, wherein cerium is present as a dopant and b is between 0.001 and 0.3. Phosphor ( 1 ) according to at least one of the preceding claims, having a Stokes shift of at least 150 nm. Phosphor ( 1 ) according to at least one of the preceding claims, having the _following empirical formula: (YLu _0.94 CaCe _0.06 ) (Mg _1.5 Al _0.5 ) (Al _0.5 Si _2.5 ) O _12. Phosphor ( 1 ) according to at least one of the preceding claims, wherein the lattice constant a has a value of between 11.9 Å inclusive and 12.1 Å inclusive. Phosphor ( 1 ) according to at least one of the preceding claims, having an absorption maximum between 450 nm and 470 nm. Phosphor ( 1 ) according to at least one of the preceding claims, comprising MgO ₆ octahedra and SiO ₄ tetrahedra, wherein at least the lattice sites of Mg are partially replaced by Al or the lattice sites of Si partially replaced by Al. Phosphor ( 1 ) according to at least one of the preceding claims, having a dominant wavelength greater than 575 nm. Phosphor ( 1 ) according to at least one of the preceding claims, having a centroid wavelength of greater than 600 nm with a half-width greater than 125 nm. Phosphor ( 1 ) according to at least one of the preceding claims, wherein RE is Y and / or Lu. Phosphor ( 1 ) according to at least one of the preceding claims, wherein a = 0.64, b = 0.02, c = 0.25 and d = 0.1667. Use of a phosphor ( 1 ) according to one of claims 1 to 12 as wavelength conversion substance ( 2 ) in an optoelectronic component ( 100 ). Use according to claim 13, wherein the optoelectronic component ( 100 ) is a light emitting diode. Process for the preparation of a phosphor ( 1 ) having the formula (RE _a Ca ₁ -ab Ce _b ) ₃ (Mg _{1 -c} Al _c ) ₂ (Al _d Si _1-d ) ₃ O ₁₂ , where RE is at least one element of rare earths, 0 ≤ a ≤ 1 , b> 0, a + b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1 and c + d> 0, comprising the steps of: A) mixing the starting materials of carbonates, oxalates, oxides, hydroxides or nitrates of B) heating the mixture obtained under A) to a temperature of over 1200 ° C, C) annealing the mixture at a temperature of about 1200 ° C under a reducing atmosphere, D) cooling the batch. A process according to claim 15, wherein the proportion of starting materials relative to the total amount of the mixture is as follows: RE ₂ O ₃ between 46% inclusive and 48% inclusive, Al ₂ O ₃ between 7% inclusive and 9% inclusive, SiO ₂ between inclusive 23% and 25% inclusive, MgO between 8% inclusive and 10% inclusive, CeO ₂ between 0.8% inclusive and 1.8% inclusive, CaO between 8% inclusive and 10% inclusive, and the total in total 100% is. The process of claim 16 wherein RE ₂ O _{3 is} a mixture of Y ₂ O ₃ and Lu ₂ O ₃ , wherein the proportion of Y ₂ O _{3 is} between 14% and 16% inclusive and the amount of Lu ₂ O _{3 is} between 31% and including 33% is.  A method according to any one of claims 15 to 17, which takes place as a solid-state reaction or sol-gel process.

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