Method for producing a powdery precursor material, powdery precursor material and use thereof

Abstract

A method can be used for producing a powdery precursor material of the following general composition I or II or III or IV: I: (Ca.sub.ySr.sub.1y) AlSiN.sub.3:X1 II:(Ca.sub.bSr.sub.aLi.sub.1ab) AISi (N.sub.1cF.sub.c)3:X2 III: Z.sub.5Al.sub.42Si.sub.8+2N.sub.18: X3 IV: (Z.sub.idLi.sub.d).sub.5Al.sub.42Si.sub.8+2(N.sub.1XF.sub.X).sub.18: X4. The method includes A) producing a powdery mixture of starting materials, wherein the starting materials comprise ions of the aforementioned compositions I and/or II and/or III and/or IV, B) annealing the mixture under a protective gas atmosphere, subsequent milling. In method step A), at least one silicon nitride having a specific area of greater than or equal to 5 m.sup.2/g and smaller than or equal to 100 m.sup.2/g is selected as starting material. The annealing in method step B) is carried out at a temperature of less than or equal to 1550 C.

Claims

1. A process for producing a pulverulent precursor material of the general composition I or II or III or IV: I: (Ca.sub.ySr.sub.1y)AlSiN.sub.3:X1 II: (Ca.sub.bSr.sub.aLi.sub.1ab)AlSi(N.sub.1cF.sub.c).sub.3:X2 III: Z.sub.5Al.sub.42Si.sub.8+2N.sub.18:X3 IV: (Z.sub.1dLi.sub.d).sub.5Al.sub.42Si.sub.8+2(N.sub.1xF.sub.x:X4 wherein X1 and X2 and X3 and X4 are each one activator or a combination of two or more activators; wherein the activator is selected from the group consisting of lanthanoids, Mn.sup.2+, Mn.sup.4+, and combinations thereof; wherein Z is selected from the group consisting of Ca, Sr, Mg, and combinations thereof; wherein: 0y1 and 0a<1 and 0b<1 and 0<c1 and ||0.5 and 0x<1 and 0d<1; the process comprising: producing a pulverulent mixture of reactants, wherein the reactants comprise ions of the compositions I and/or II and/or III and/or IV, wherein a silicon nitride having a specific surface area of greater or equal than 5 m.sup.2/g and less or equal than 100 m.sup.2/g is selected as a reactant; calcining the mixture under a protective gas atmosphere and at a temperature less than or equal to 1550 C.; and grinding the calcined mixture, wherein the pulverulent precursor material of the general composition I or II or III or IV is produced, wherein the pulverulent precursor material has a first grain size value d.sub.50 and a second grain size value d.sub.90, and wherein the first grain size value d.sub.50 is less or equal than 2 m and the second grain size value d.sub.90 is less or equal than 3.5 m.

2. The process according to claim 1, wherein the calcining is conducted at a temperature between 1200 C. and 1450 C.

3. The process according to claim 1, wherein the calcining is conducted at a temperature between 1200 C. and 1550 C.

4. The process according to claim 1, wherein the silicon nitride has a specific surface area in a range from 10 m.sup.2/g to 30 m.sup.2/g.

5. The process according to claim 1, wherein AlN is a reactant of the mixture of reactants, wherein AlN has a specific surface area of 1 to 25 m.sup.2/g.

6. The process according to claim 1, wherein reactants used in producing the pulverulent mixture of reactants are selected from the group consisting of carbonates, oxides, nitrides, carbides, metals and halides and combinations thereof.

7. The process according to claim 1, wherein the silicon nitride is semicrystalline or crystalline.

8. The process according to claim 1, wherein the calcining is conducted from one to five times.

9. The process according to claim 1, wherein the calcining includes a hold time between 1 minute and 24 hours.

10. The process according to claim 1, further comprising washing the pulverulent precursor material in alkali and/or acid after the calcining.

11. A pulverulent precursor material produced by a process according to claim 1.

12. The pulverulent precursor material according to claim 11, wherein the pulverulent precursor material has the first grain size value d.sub.50 and the second grain size value d.sub.90, and wherein the first grain size value d.sub.50 has a value of 10.3 m and the second grain size value d.sub.90 has a value of 30.3 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and advantageous embodiments of the process, the pulverulent precursor material and the use thereof will become apparent from the inventive examples and figures which follow.

(2) FIG. 1 shows a first grain size value d.sub.50 and a second grain size value d.sub.90 of the pulverulent precursor material of embodiments and of comparative examples, and

(3) FIG. 2 shows a schematic side view of an optoelectronic component according to one embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(4) Specified hereinafter are comparative examples C1, C2 and C3 for production of a coarse-grained precursor material and inventive examples I1, I2 and I3 for production of finely divided pulverulent precursor materials.

COMPARATIVE EXAMPLE C1

Production of CaAlSiN3:Eu

(5) 50 g of Ca.sub.3N.sub.2, 41 g of AlN, 47 g of Si.sub.3N.sub.4 (specific surface area about 11 m.sup.2/g) and 5 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1550 C. and 1800 C. for several hours. This may be followed by further calcinations to adjust the grain size or the grain size value, likewise under a reducing atmosphere, between 1550 C. and 1800 C. After subsequent grinding and sieving of the calcined cake, the result is a coarse-grained luminophore having the general formula CaAlSiN.sub.3:Eu. The coarse-grained luminophore illustrated in FIG. 1 and in table 1, after processing, has a first grain size value d.sub.50 of 9.4 m and a second grain size value d.sub.90 of 15.8 m.

COMPARATIVE EXAMPLE C2

Production of CaAlSiN3:Eu

(6) 50 g of Ca.sub.3N.sub.2, 41 g of AlN, 47 g of amorphous Si.sub.3N.sub.4 (specific surface area about 110 m.sup.2/g) and 5 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1300 C. and 1800 C., for example, at 1450 C., for several hours. This may be followed by further calcinations to adjust the grain size or the grain size value, likewise under a reducing atmosphere, between 1300 C. and 1800 C., for example, at 1450 C. After subsequent grinding and sieving of the calcined cake, the result is a coarse-grained luminophore (see table 1).

COMPARATIVE EXAMPLE C3

Production of CaAlSiN3:Eu

(7) 50 g of Ca.sub.3N.sub.2, 41 g of AlN, 47 g of amorphous Si.sub.3N.sub.4 (specific surface area about 103 to 123 m.sup.2/g) and 5 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1300 C. and 1800 C., for example, at 1450 C., for several hours. This may be followed by further calcinations to adjust the grain size or the grain size value, likewise under a reducing atmosphere, between 1300 C. and 1800 C., for example, at 1450 C. After subsequent grinding and sieving of the calcined cake, the result is a coarse-grained luminophore. The coarse-grained luminophore has a first grain size value d.sub.50 of 2.3 m and a second grain size value d.sub.90 of 4.9 m (FIG. 1 and table 1).

INVENTIVE EXAMPLE I1

Production of CaAlSiN3:Eu

(8) 82 g of Ca.sub.3N.sub.2, 68 g of AlN, 78 g of Si.sub.3N.sub.4 (specific surface area about 11 m.sup.2/g) and 1 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1300 C. and 1550 C. for several hours. After subsequent grinding and sieving of the calcined cake, the result is a fine-grained and very reactive pulverulent precursor material. This precursor material can be used for ceramic materials. This pulverulent precursor material consists, as well as the CaAlSiN.sub.3:Eu phase, of the CaSiN.sub.2:Eu intermediate and as yet unreacted AlN. The latter are converted fully in the course of ceramic production to the desired CaAlSiN.sub.3:Eu.

INVENTIVE EXAMPLE I2

Production of CaAlSiN3:Eu

(9) 82 g of Ca.sub.3N.sub.2, 68 g of AlN, 78 g of Si.sub.3N.sub.4 (specific surface area about 13 m.sup.2/g) and 1 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1300 C. and 1550 C. for several hours. After subsequent grinding and sieving of the calcined cake, the result is a fine-grained and reactive CaAlSiN.sub.3:Eu. The pulverulent precursor material has a first grain size value d.sub.50 of 1.2 m and a second grain size value d.sub.90 of 2.9 m. X-ray diffraction (XRD) confirms the phase purity of the pulverulent precursor material.

INVENTIVE EXAMPLE I3

Production of CaAlSiN3:Eu

(10) 82 g of Ca.sub.3N.sub.2, 68 g of AlN, 78 g of Si.sub.3N.sub.4 (specific surface area about 14 m.sup.2/g) and 1 g of Eu.sub.2O.sub.3 are weighed out and homogenized under a protective gas atmosphere. Subsequently, the reactant mixture is calcined in slightly compacted form under a reducing atmosphere in a tubular or chamber furnace at temperatures between 1300 C. and 1550 C. for several hours. After subsequent grinding and sieving of the calcined cake, the result is a fine-grained and reactive CaAlSiN.sub.3:Eu. The pulverulent precursor material has a first grain size value d.sub.50 of 1.3 m and a second grain size value d.sub.90 of 3.3 m. X-ray diffraction (XRD) confirms the phase purity of the pulverulent precursor material.

(11) FIG. 1 shows, for the corresponding comparative examples C1, C2-1, C2-2 and C3 and the inventive examples I1-1, I1-2, I2 and I3, a graph of a first grain size value d.sub.50 in m and a second grain size value d.sub.90 in m at the corresponding hold time t in hours h, maximum temperature or maximum calcination temperature T.sub.max in C. and specific surface area A of the Si.sub.3N.sub.4 in m.sup.2/g. Table 1 additionally shows the quantum efficiency Q.E. in % of the pulverulent precursor material. Comparative examples C2-1 and C2-2 were produced analogously to comparative example C2, with adjustment of the parameters such as the specific surface area A of Si.sub.3N.sub.4 in m.sup.2/g, maximum calcination temperature T.sub.max in C. and/or maximum hold time t in h, according to table 1. The procedure was analogous in the case of inventive examples I1-1 and I1-2. Table 1 additionally shows the first grain size value d.sub.50 in m, the second grain size value d.sub.90 in m and the quantum efficiency Q.E. in % for the pulverulent precursor material according to one embodiment and of comparative examples. The Q.E. was determined in each case by powder tablet analysis.

(12) TABLE-US-00001 TABLE 1 T.sub.max in d.sub.50 d.sub.90 Q.E. in A in m.sup.2/g C. t in h in m in m % C1 11 1580 4 9.4 15.8 83 C2-1 110 1550 4 5.8 16.1 69 C2-2 110 1450 4 2.0 4.6 67 C3 103 to 123 1450 2 2.3 4.9 51 I1-1 11 1450 4 1.4 3.3 77 I1-2 11 1450 2 1.1 3.0 68 I2 13 1450 2 1.2 2.9 70 I3 14 1450 2 1.3 3.3 70

(13) It can be inferred from table 1 that, when using an Si.sub.3N.sub.4 having a specific surface area of greater or equal than 5 m.sup.2/g and less or equal than 100 m.sup.2/g as reactant and a calcining temperature in process step B) of less or equal than 1550 C., it is possible to produce a finely distributed pulverulent precursor material having a very small first grain size value d.sub.50 and/or a second grain size value d.sub.90 with correspondingly high quantum efficiency. The hold time is between 2 and 4 hours.

(14) Table 2 below shows the influence of the specific surface area AA of aluminum nitride AlN in m.sup.2/g on the first grain size value d.sub.50 and second grain size value d.sub.90 of the finely distributed pulverulent precursor material. The specific surface area of about 11 m.sup.2/g of silicon nitride was kept constant in all the experiments. It is apparent from table 2 that a small specific surface area of aluminum nitride, especially a specific surface area of 3.6 m.sup.2/g, leads to small grain sizes or grain size values. For example, a pulverulent precursor material which has been produced with aluminum nitride having a specific surface area of 3.1 to 3.6 m.sup.2/g exhibits a first grain size value d.sub.50 of 1.1 m and a second grain size value d.sub.90 of 3.9 m.

(15) TABLE-US-00002 TABLE 2 AA in m.sup.2/g T.sub.max in C. t in h d.sub.50 in m d.sub.90 in m 3.1 to 3.6 1450 2 1.1 3.0 >115 1450 2 4.3 17.8 2.3 to 2.9 1450 2 1.4 4.2

(16) It has been shown that it is possible via the specific surface area of the nitrides (reactants) and the suitably selected temperature to selectively produce a pulverulent precursor material and to control its sintering properties and its grain size. It is thus possible to influence the packing density in tape casting, for example, via the particle size. In general, precursors having a high d.sub.90 value or second grain size value are difficult to process or improcessible in ceramic production or have to be reprocessed in complex grinding operations which lead to efficiency losses and impurities.

(17) FIG. 2 shows a schematic side view of an optoelectronic component 100 using the working example of a light-emitting diode (LED). The optoelectronic component 100 has a layer sequence 1 with an active region (not shown explicitly), a first electrical connection 2, a second electrical connection 3, a bonding wire 4, an encapsulation 5, a housing wall 7, a housing 8, a recess 9, a precursor material 6 for formation of a ceramic layer 11 or wavelength conversion layer 11 and a matrix material 10. The layer sequence 1 having an active region comprising the wavelength conversion layer 11 is disposed within the optoelectronic component, the encapsulation 5 and/or the recess 9. The first and second electrical connections 2, 3 are disposed beneath the layer sequence 1 having an active region. There is indirect and/or direct electrical and/or mechanical contact between the layer sequence 1 having an active region and the bonding wire 4, and between the layer sequence 1 having an active region and the first and/or second electrical connection(s) 2, 3.

(18) In addition, the layer sequence 1 having an active region may be disposed on a carrier (not shown here). A carrier may, for example, be a printed circuit board (PCB), a ceramic substrate, another circuit board or a metal sheet, for example, aluminum sheet.

(19) Alternatively, a carrier-free arrangement of the layer sequence 1 is possible in the case of what are called thin-film chips.

(20) The active region is suitable for emission of electromagnetic primary radiation in an emission direction. The layer sequence 1 having an active region may be based, for example, on nitride compound semiconductor material. Nitride compound semiconductor material emits particularly electromagnetic primary radiation in the blue and/or ultraviolet spectral region. More particularly, InGaN can be used as nitride compound semiconductor material having electromagnetic primary radiation having a wavelength of 460 nm.

(21) The wavelength conversion layer 11 is disposed in the beam path of the electromagnetic primary radiation. The matrix material 10 is, for example, polymeric or ceramic material. In this case, the wavelength conversion layer 11 is disposed in direct mechanical and/or electrical contact on the layer sequence 1 having an active region.

(22) Alternatively, further layers and materials, for example, the encapsulation, may be disposed between the wavelength conversion layer and the layer sequence 1 (not shown here).

(23) Alternatively, the wavelength conversion layer 11 may be disposed indirectly or directly on the housing wall 7 of a housing 8 (not shown here).

(24) Alternatively, it is possible that the precursor material is embedded in a potting compound (not shown here) and takes the form of an encapsulation 5 together with a further material, for example, a diffuser, 10.

(25) The wavelength conversion layer 11 at least partly converts the electromagnetic primary radiation to an electromagnetic secondary radiation. For example, the electromagnetic primary radiation emits in the blue spectral region of the electromagnetic radiation, with conversion of at least some of this electromagnetic primary radiation by the wavelength conversion layer 11 to an electromagnetic secondary radiation in the red and/or green spectral region and/or combinations thereof. The total radiation emitted from the optoelectronic component is a superimposition of blue-emitting primary radiation and red- and green-emitting secondary radiation, the overall emission visible to the outside observer being white light.

(26) The wavelength conversion layer 11 may take the form of a ceramic or powder and may convert the electromagnetic primary radiation fully to electromagnetic secondary radiation. In this case, the electromagnetic secondary radiation is in the red spectral region.

(27) According to at least one embodiment, the red-emitting wavelength conversion layer 11 takes the form of a ceramic and is disposed in an optoelectronic component additionally with a yellow- and/or green-emitting luminophore in the form of a powder. More particularly, the optoelectronic component has an overall emission which is perceived as white light by an outside observer.

(28) According to at least one embodiment, the red-emitting wavelength conversion layer 11 takes the form of a ceramic and is disposed in an optoelectronic component additionally or alternatively with a yellow- and/or green-emitting luminophore in the form of a ceramic. More particularly, the optoelectronic component has an overall emission which is perceived as white light by an outside observer.

(29) According to at least one embodiment, the red-emitting wavelength conversion layer 11 takes the form of a powder and is disposed in an optoelectronic component additionally with a yellow- and/or green-emitting luminophore in the form of a ceramic. More particularly, the optoelectronic component has an overall emission which is perceived as white light by an outside observer.

(30) According to at least one embodiment, the red-emitting wavelength conversion layer 11 takes the form of a powder and is disposed in an optoelectronic component additionally with at least one yellow- and/or green-emitting luminophore in the form of a powder. More particularly, the optoelectronic component has an overall emission which is perceived as white light by an outside observer.

(31) According to at least one embodiment, the primary radiation has a wavelength from the UV spectral region. The wavelength conversion layer 11 may take the form of a ceramic or powder and be disposed in an optoelectronic component additionally with a yellow- and/or green-emitting luminophore in the form of a ceramic or powder and with a blue-emitting luminophore in the form of a ceramic or powder. More particularly, the optoelectronic component has an overall emission which is perceived as white light by an outside observer.

(32) The invention is not restricted by the description with reference to the working examples; instead, the invention encompasses every new feature and every combination of features, which especially includes every combination of features in the claims, even if this feature or this combination itself is not specified explicitly in the claims or working examples.