METHOD FOR REDUCING DARKNESS IN FLUORINE-IN-GLASS (PIG) ​​MADE BY SPS

Abstract

A method for producing a glass composite wavelength converter, comprising: providing at least one phosphor material, providing a powder of glass components, mixing the phosphor material and the powder of glass components to produce a first mixture, adding at least one oxidizing agent to the first mixture, the oxidizing agent being selected from the group consisting of NaNO3, KNO3, LiNO3, Na2SO3, K2SO3, LiSO3 and K2MnO4, mixing the oxidizing agent with the first mixture to produce a second mixture, and applying pressure and charge to the second mixture to produce a glass composite wavelength converter.

Description

TECHNICAL AREA

[0001] This invention relates to a method for manufacturing a glass wavelength converter, a glass wavelength converter, and a light source comprising the glass wavelength converter. The glass wavelength converter is preferably a so-called phosphor-in-glass (PiG) wavelength converter. BACKGROUND

[0002] There are several approaches to manufacturing phosphor wavelength converter materials. In the fabrication of conventional light-emitting diodes using phosphor conversion (pc-LEDs), phosphor powders are typically mixed with a polymer material, such as a silicone or epoxy resin, to create a homogeneous dispersion of the phosphor particles within the resin. The phosphor polymer mixtures are then cast, applied, or layered onto a blue-emitting (or near-ultraviolet-emitting) LED chip in an LED package. While the phosphor polymer mixture approach is easily implemented in LED packages, it often suffers from the instability of the polymer materials, which can degrade under high temperatures and light intensities.

[0003] Another way to manufacture a PC-LED is by using a ceramic wavelength converter. Ceramic wavelength converters are formed by sintering a mass of inorganic phosphor particles at high temperature until the particles diffuse and bond together to form a monolithic part. The ceramic converter is typically formed as a thin rectangular plate deposited onto the light-emitting surface of the LED chip. Due to their higher thermal conductivity, ceramic wavelength converters are preferred in high-power applications over converters formed from dispersions of phosphor particles in epoxy or silicone resins. While this approach offers better stability, it is more expensive to manufacture.

[0004] The phosphor-in-glass (PiG) approach lies somewhere between these two approaches. It offers the flexibility of the phosphor-polymer approach and the superior stability of the ceramic converter approach at a lower cost. Typically, phosphor-in-glass approaches require the glass to soften or melt to ensure homogeneity of the phosphor dispersion and to reduce or eliminate porosity in the converter. However, due to the temperatures and residence times used in these processes, the potential for phosphor damage is increased. This is less of a concern for oxide-based phosphors, such as cerium-doped yttrium aluminum garnet phosphors, as these are less sensitive to such process conditions.However, the damage to nitride-based phosphors can be severe, especially since nitride-based phosphors are very sensitive to oxygen impurities and most glasses are oxide glasses, an abundant source of oxygen.

[0005] PiG is used in LED packages. It can absorb all or part of the excitation light, such as blue or near-UV light, from an LED chip and convert it into light of a different wavelength. One way to produce PiG samples is by using Spark Plasma Sintering (SPS). This offers several advantages compared to other conventional pressureless sintering methods. First, due to the additional pressure applied, SPS of PiG is performed at a much lower temperature than pressureless sintering. This results in less damage to the phosphors used in the PiG. Second, PiG produced by SPS can have lower porosity, again due to the pressure used. Because of these advantages, PiG produced by SPS can have better performance than PiG produced by pressureless sintering.

[0006] However, during SPS of a glass powder process, some glasses exhibit darkening. There are two possible sources for this darkening. During an SPS process, the samples are in contact with a graphite die and foil used in the manufacturing setup. Although a BN protective coating has been applied to the inner side of the dies and foil, some darkening may still occur due to graphite contamination. The second possible reason for the darkening is the reduced atmosphere used in SPS processes. During the SPS process, carbon present in parts of the manufacturing setup could react with residual oxygen in the SPS chamber. The reaction products could be CO or CO2. The gaseous CO and CO2 can diffuse into samples and may become trapped in sample pores. If the temperature and pressure increase, the reaction could occur according to equation (1). 2 CO(g) → CO2(g) + C (1)

[0007] The carbon particles trapped within the pores cause a darkening effect. Additionally, CO could also reduce metal ions in the glass to metallic elements, leading to darkening.

[0008] “A Comprehensive Study of the Carbon Contamination in Tellurite Glasses and Glass-Ceramics Sintered by Spark Plasma Sintering (SPS)” is in J. Am. Ceram. Soc., 97 [1] 163-172 (2013).

[0009] WO 2016 / 209871 discloses glass composite wavelength converters manufactured by Spark Plasma Sintering. SUMMARY

[0010] It is an object of the invention to avoid the disadvantages of the prior art. Preferably, a method of the present invention would significantly reduce the darkening in PiG samples and thus increase the efficiency of the PiG samples.

[0011] Another object of the present invention is to provide a method for manufacturing a glass composite wavelength converter.

[0012] It is also an object of the present invention to provide a glass composite wavelength converter produced by a method of the present invention.

[0013] It is also an object of the present invention to provide a light source comprising a glass composite wavelength converter, manufactured by a method of the present invention.

[0014] According to an object of the present invention, a method for manufacturing a glass composite wavelength converter is provided, comprising the steps of: provide at least one fluorescent material, providing a powder of glass components, Mixing the phosphor material and the powder of glass components to create an initial mixture, Adding at least one oxidizing agent to the first mixture, Mixing the oxidizing agent with the first mixture to produce a second mixture, Applying pressure and charge to the second mixture, thereby producing a glass composite wavelength converter.

[0015] According to another subject matter of the present invention, a glass composite wavelength converter produced by a method of the present invention is provided.

[0016] According to another aspect of the present invention, a light source is provided, comprising: a light-emitting diode (LED) that emits a primary light; and a glass composite wavelength converter manufactured by a process comprising the steps of: provide at least one fluorescent material, providing a powder of glass components, Mixing the phosphor material and the powder of glass components to create an initial mixture, Adding at least one oxidizing agent to the first mixture, Mixing the oxidizing agent with the first mixture to produce a second mixture, Applying pressure and charge to the second mixture, thereby producing a glass composite wavelength converter, whereby the phosphor material converts at least part of the primary light into secondary light. List of characters

[0017] The invention is explained in more detail below based on the examples and with reference to the accompanying figures. The figures are schematic and are not to scale. Fig. 1a-1e represent glass samples produced by PLC; Fig. 2a-2c represent glass samples produced by PLC; Fig. 3a-3c represent fluorescent-in-glass samples produced by PLC; Fig. 4 describes a method for manufacturing a glass composite wavelength converter; and Fig. 5 represents a light source DETAILED DESCRIPTION OF ILLUSTRATIVE EXECUTIONS

[0018] For a better understanding of the present invention, together with other and further subject matter, advantages and possibilities thereof, reference is made to the present disclosure and the attached patent claims together with the drawings described above.

[0019] References to the color of the phosphor, LED, or conversion material generally refer to its emission color unless otherwise specified. Thus, a blue LED emits blue light, a yellow phosphor emits yellow light, and so on.

[0020] The present invention relates to a method 10 for the manufacture of a glass composite wavelength converter, as in Fig. 4 shown, directed, comprehensive the steps of: provide at least one fluorescent material 12 , providing a powder of glass components 14 , Mixing the phosphor material and the powder of glass components to create an initial mixture 16 , Adding at least one oxidizing agent to the first mixture 18 , Mixing the oxidizing agent with the first mixture to produce a second mixture 20 , Applying pressure and charge to the second mixture 22 , thereby producing a glass composite wavelength converter.

[0021] As used herein, a wavelength converter is a solid structure that converts at least some of a light of a given first wavelength into light of a given second wavelength.

[0022] According to the present invention, the method comprises the step of providing at least one phosphor material. A phosphor is a material that converts light of a specific first wavelength into light of a specific second wavelength.

[0023] In one embodiment of the present invention, the phosphor material can be an oxide-based phosphor or a nitride-based phosphor. Oxide-based phosphors can include cerium-activated garnet phosphors, which are described by the formula A3B5O 12 :Ce can be represented, where AY, Sc, La, Gd, Lu, or Tb and B is AI, Ga, or Sc. Preferably, the oxide-based phosphor is at least one of Y3Al s O 12 :Ce (abbreviation YAG:Ce), (Y,Gd)3Al5O 12 :Ce (abbreviation YGdAG:Ce), and Lu3Al5O 12 :Ce (abbreviated LuAG:Ce). Examples of nitride-based phosphors include MAISiN3:Eu, where M is selected from Ca, Sr, and Ba, and M2Si5N8:Eu, where M is selected from Ca, Sr, and Ba. Other possible phosphors include oxynitride phosphors, such as MSi2O2N2:Eu, where M is selected from Ca, Sr, and Ba, and silicate phosphors, such as BaMgSi4O4:Eu and M2SiO4:Eu, where M is selected from Ca, Sr, and Ba.

[0024] In a preferred embodiment, the phosphor material is a red phosphor, and even more preferably, a red narrowband phosphor. Red phosphors are important for producing a warm white color and a high color rendering index in phosphor-converted LEDs. They can also be used for full-conversion red LEDs, where red phosphors absorb all the blue / UV light from the LED chip and convert it into red emission. Examples of red phosphors are MAISiN3:Eu, where M is selected from Ca, Sr, and Ba, and M2Si5N8:Eu, where M is selected from Ca, Sr, and Ba.

[0025] Other preferred phosphor materials are YAG:Ce, e.g. for cool white LEDs, YAG:Ce and MAISiN3:Eu, e.g. for warm white LEDs, where M is selected from Ca, Sr and Ba.

[0026] The phosphor material can be present as a pure material, or it can be present as a mixture of at least two different phosphor materials.

[0027] The phosphor material can be present in an amount of approximately 10 wt.% to approximately 50 wt.%, preferably approximately 15 wt.% to approximately 30 wt.%, based on the second mixture. The exact amount of phosphor required may depend on the type of phosphor (e.g., the type and / or concentration of the activator in the phosphor), the final thickness of the sample, and / or the target color classification.

[0028] The method of the present invention further comprises the step of mixing the phosphor material and a powder of glass components, thereby producing a first mixture.

[0029] The powder of the glass components can have a particle size of approximately 1 µm to approximately 40 µm. In one embodiment, the powder of the glass components has a particle size of approximately 3 µm to approximately 5 µm.

[0030] In one embodiment of the present invention, the glass components have a glass transition temperature of less than approximately 600 °C. In another embodiment of the present invention, the glass components have a glass transition temperature of less than approximately 400 °C. In a further embodiment of the present invention, the glass components have a glass transition temperature of less than approximately 300 °C.

[0031] The glass components can be selected from the group consisting of RO-B2O3-Al2O3-SiO2, RO-B2O3-SiO2, or RO-P2O5, where R is selected from Mg, Ca, Sr, Ba, Zn and Sn.

[0032] The glass components should be selected to result in essentially transparent glass. Essentially transparent glass means that the glass preferably transmits at least approximately 80%, more preferably at least approximately 90%, or even more preferably at least approximately 95% of the primary and secondary light. The glass should preferably be resistant to devitrification. For example, if it devitrifies easily during the manufacturing process, the resulting crystalline phases can act as scattering / absorption centers, resulting in light loss. It is also preferred that the glass be moisture- and weather-resistant.

[0033] In one embodiment, the phosphor material can be YAG:Ce and the glass components can be RO-B2O3-Al2O3-SiO2, where R is selected from the alkaline earth metals Mg, Ca, Sr, and Ba. In an alternative embodiment, the phosphor materials are YAG:Ce and MAISiN3:Eu and the glass components are RO-P2O5, where M is selected from Ca, Sr, and Ba and R is selected from Zn, Sn, Mg, Ca, Sr, and Ba.

[0034] In a further step of the process according to the present invention, an oxidizing agent is added to the first mixture comprising a phosphor material and a powder of glass components. The oxidizing agent, the phosphor material, and the glass components can also be mixed in a single step rather than in a subsequent step. For example, it is also possible that the oxidizing agent is provided and the phosphor material and the glass components are added.

[0035] In one embodiment of the present invention, the oxidizing agent is selected from the group consisting of NaNO3, KNO3, LiNO3, Na2SO3, K2SO3, LiSO3, and K2MnO4.

[0036] As mentioned above, the darkening in the glass during SPS sintering is caused by a reduced atmosphere containing CO. Adding some oxidizing agent to the glass component powders should help reduce the darkening by oxidizing CO to CO2. Thus, if reaction (1) does not occur, no carbon will be trapped in the glass, nor will any metal ions be reduced to elemental metal.

[0037] For example, if NaNO3 is used as an oxidizing agent, the NaNO3 can be decomposed during the process of the present invention, e.g., during SPS sintering. One of the byproducts is O2, which can oxidize CO to CO2 and thereby reduce the darkening in the final product.

[0038] NaNO3 could decompose as follows: 2 NaNO3 → 2 NaNO2 + O2 (2) 2 NaNO3 → Na2O + 3 / 2 O2 + 2NO (3)

[0039] In one embodiment, the oxidizing agent is added to the first mixture in an amount of less than approximately 3 wt.%, based on the amount of the second mixture. In an alternative embodiment, the oxidizing agent is added to the first mixture in an amount of less than approximately 2 wt.%, based on the amount of the second mixture. In another alternative embodiment, the oxidizing agent is added to the first mixture in an amount of less than approximately 1 wt.%, based on the amount of the second mixture. In a further alternative embodiment, the oxidizing agent is added to the first mixture in an amount of less than approximately 0.5 wt.%, based on the amount of the second mixture.

[0040] The method according to the present invention further comprises the step of applying pressure and charge to the second mixture, comprising the oxidizing agent, the phosphor material, and the powder of the glass components. The application of pressure and charge leads to sintering of the components of the second mixture. During sintering, the powder of the glass components melts, preferably resulting in a transparent melt into which the phosphor material is preferably homogeneously mixed.

[0041] The method of the present invention is preferably a so-called SPS (Single-Sintered Sintering) process. The sintering temperature in the SPS process is much lower compared to other prior art methods in which glasses are heated to a high temperature, causing them to soften or melt. The lower sintering temperature reduces potential damage to the phosphors, while, when using a pressure sintering process, it keeps the porosity low.

[0042] The pressure applied to the second mixture could be at least approximately 30 MPa, preferably at least approximately 40 MPa, more preferably at least approximately 50 MPa.

[0043] In addition to pressure, a charge is applied in the process of the present invention. In a so-called SPS process, pressure is applied to the graphite matrix containing the second mixture. The application of charge leads to an increase in the temperature of the second mixture. The applied charges are typically hundreds of amperes, depending on the target sintering temperature. Preferably, the applied charges are up to 1500 A.

[0044] In one embodiment, an inert atmosphere is used in the process according to the present invention. Preferably, in the case of an SPS process, an inert atmosphere is used in the SPS furnace chamber, which comprises the second mixture. In other words, the existing atmosphere, which typically includes oxygen, is replaced by an inert atmosphere. Typical inert atmospheres are nitrogen or argon, with nitrogen being preferred.

[0045] Preferably, the glass composite wavelength converter has a quantum efficiency of at least approximately 80%. In one embodiment, the glass composite wavelength converter has a quantum efficiency of at least approximately 90%. In a preferred embodiment, the glass composite wavelength converter has a quantum efficiency of at least approximately 95%.

[0046] Another object of the present invention is to provide a glass composite wavelength converter produced by a method according to the present invention.

[0047] The phosphor material, the glass components and the oxidizing agents correspond to the respective components and materials mentioned above.

[0048] ZB is the phosphor material of the glass composite wavelength converter YAG:Ce.

[0049] In one embodiment, the glass components of the glass wavelength converter are selected from RO-B2O3-Al2O3-SiO2, where R is selected from alkaline earth metals Mg, Ca, Sr and Ba.

[0050] Another object of the present invention is a light source. 30 to make available, as in Fig. 5 shown, comprehensively: a light-emitting diode (LED) 32 , which emits a primary light; and a glass composite wavelength converter 34 produced by a process encompassing the steps of: provide at least one fluorescent material, providing a powder of glass components, Mixing the phosphor material and the powder of glass components to create an initial mixture, Adding at least one oxidizing agent to the first mixture, Mixing the oxidizing agent with the first mixture to produce a second mixture, Applying pressure and charge to the second mixture, thereby producing a glass composite wavelength converter, wherein the phosphor material converts at least part of the primary light into secondary light.

[0051] A light-emitting diode (LED) of a light source according to the present invention typically emits blue light or UV light. Preferred LEDs are blue-light LEDs.

[0052] The components of the glass composite wavelength converter and the process steps correspond to the components and steps as described above.

[0053] In one embodiment, the phosphor material of the light source is YAG:Ce.

[0054] In another embodiment, the oxidizing agent of the light source is NaNO3.

[0055] The glass composite wavelength converter of the light source has a quantum efficiency of at least approximately 80%, preferably at least approximately 90%, more preferably at least approximately 95%.

[0056] The glass composite wavelength converters, as well as the light sources, can be used in general lighting, automotive lighting, projection lighting, etc.

[0057] Fig. Figures 1a-1e show different glasses produced by PLC.

[0058] Fig. 1a is a TeO2 glass, produced at a temperature of 300 °C and a pressure of 50 MPa (the temperature and pressure are held for less than 1 minute).

[0059] Fig. 1b is a PbO-ZnO-B2O3 glass produced at a temperature of 350 °C and a pressure of 50 MPa (the temperature and pressure are held for 5 minutes).

[0060] Fig. 1c is a lime-soda glass produced at a temperature of 480 °C and a pressure of 50 MPa (the temperature and pressure are held for 1 minute).

[0061] Fig. 1d is an alkaline earth aluminosilicate glass (Schott 8252) produced using SPS at a temperature of 610 °C at a pressure of 50 MPa (the temperature and pressure are held for less than 1 minute).

[0062] Fig. 1e is a borosilicate glass (Borofloat33) produced using SPS at a temperature of 600 °C at a pressure of 50 MPa (the temperature and pressure are held for 0.5 minutes).

[0063] In Fig. 1a to Fig. 1e The degree of darkening obviously varies and appears to depend on the glass composition. Some glasses containing tellurium and lead turn black when exposed to SPS ( Fig. 1a and Fig. 1b) The metal ions in the glass could be reduced to metallic elements by CO during the SPS sintering, which could cause the darkening.

[0064] From the degree of darkening of the above glasses, shown in Fig. 1a to Fig. Equation 1e implies that direct contact with the graphite matrix cannot be the primary cause of the darkening in the glass. The reduced atmosphere containing CO₂ is another contributing factor. During the preparation of PiG samples, any darkening in the glass matrix will absorb light and thus reduce the PiG efficiency.

[0065] Fig. 2a-2c show alkaline earth boroaluminosilicate glasses (Ca,Ba)O-B2O3-Al2O3-SiO2.

[0066] Fig. 2a and Fig. 2b represent glasses which were sintered by PLC without the addition of NaN03.

[0067] Fig. 2c represents a glass, manufactured by PLC according to Fig. 2a and Fig. 2b, however with the addition of 1 wt.% NaN03 fine powder.

[0068] It has been clearly demonstrated that glass 2c with a NaN03 additive exhibits significantly reduced darkening. The NaN03 can be decomposed during SPS sintering, as described above. This example illustrates the effect of NaN03 on reducing darkening in glass produced by an SPS process.

[0069] PiG samples using YAG:Ce phosphor in alkaline earth boroluminosilicate glass, with and without the addition of NaNO3 to the phosphor-glass powder mixture, were fabricated by a SPS process and tested. Table 1 lists three PiG samples from this test. Sample A has no NaNO3 addition, while samples B and C each have 1 wt% NaNO3 added to the phosphor powder mixture. "v%" refers to volume percent relative to the total volume of the second mixture. "D" represents the density of the glass composite wavelength converter. Cx and Cy represent the color measured using a blue LED as the excitation source. "QE" represents the quantum efficiency measured at 460 nm. "Abs" represents the absorption at 700 nm. The last column of Table 1 specifies the conditions for the SPS, such as the temperature, pressure, and holding time of these conditions.

[0070] Fig. Figures 3a-3c show the PiG samples prepared with and without the addition of NaNO3 as an oxidizing agent according to Table 1. Fig. 3a (Sample A) the color of the sample is a little darker, while samples B ( Fig. 3b) and Fig. C ( Fig. 3c) have a brighter yellow color. The quantum efficiency at 460 nm of sample A is only 78.8% and the absorption at 700 nm is 11.8%. The quantum efficiency of samples B and C is increased to 95.4% and 96.1%, respectively, and their absorptions are reduced to 2.1% and 1.7%. The conversion efficiency also shows an improvement compared to a sample without the addition of NaNO3. Examples

[0071] Sample 1: Fluorescent-in-glass (PiG) Sample A (without NaNO3):

[0072] 1.7 grams of glass powder, a type of alkaline earth boroaluminosilicate glass (30.3 mol% (BaO, ZnO, CaO) - 5.6 mol% B₂O₃ - 4.0 mol% Al₂O₃ - 60.2 mol% SiO₂), were mixed by hand with 0.4 grams of phosphor powder (a type of YAG:Ce phosphor) using an agate mortar and pestle. The powder mixture was then further blended in a plastic container using a Thinky Mixer ARE-500 at 1000 rpm for 2 minutes. 0.7 grams of the blended powder were transferred to a graphite matrix with a 15 mm inner diameter. The samples were sintered using SPS Syntex Inc.'s Dr. Sinter LAB SPS furnace, model SPS515, with a maximum force of 50 kN and a maximum charge of 1500 A. The sample was sintered under a nitrogen atmosphere. The sample was sintered at a peak temperature of 570°C with a holding time of 1 minute and an applied pressure of 65 MPa.

[0073] The sintered PiG disk was cut and ground and lapped to a thickness of approximately 126 µm.

[0074] Sample 2: Fluorescent-in-glass (PiG) Sample C (with NaNO3):

[0075] 1.7 grams of glass powder, a type of alkaline earth boroaluminosilicate glass, 30.3 mol% (BaO, ZnO, CaO) - 5.6 mol% B₂O₃ - 4.0 mol% Al₂O₃ - 60.2 mol% SiO₂, were mixed by hand with 0.4 grams of phosphor powder (a type of YAG:Ce phosphor) and 0.021 grams of NaNO₃ using an agate mortar and pestle. The powder mixture was then further mixed in a plastic container in a Thinky Mixer ARE-500 at 1000 rpm for two minutes. 0.7 grams of the mixed powder were transferred to a graphite matrix with an inner diameter of 15 mm. The sample was sintered in the same SPS furnace as in Example 1. The sample was sintered under a nitrogen atmosphere. The sample was sintered at a peak temperature of 583°C with a holding time of a few seconds and an applied pressure of 50 MPa.

[0076] The sintered PiG disk was cut and ground and lapped to an average thickness of approximately 125 µm.

[0077] As can be seen through the use of the oxidizing agent, the darkening in phosphor-in-glass samples can be significantly reduced and the performance can be increased, such as the efficiency of the phosphor-in-glass samples and thus of the glass composite wavelength converter.

[0078] While the currently preferred embodiments of the invention have been shown and described, it is obvious to the person skilled in the art that various changes and modifications can be made here without deviating from the scope of the invention as defined in the attached claims. The disclosure encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the attached claims, even if the feature or combination is not explicitly stated in the claims or examples.

[0079] This patent application claims priority from US patent application 16 / 269,443, the contents of which are hereby incorporated by reference. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2016 / 209871

[0009] US 16269443

[0079] Cited non-patent literature

[0000] “A Comprehensive Study of the Carbon Contamination in Tellurite Glasses and Glass-Ceramics Sintered by Spark Plasma Sintering (SPS)” is in J. Am. Ceram. Soc., 97 [1] 163-172 (2013)

[0008]

Claims

[1] Method for manufacturing a glass composite wavelength converter, the method comprising: provide at least one fluorescent material, providing a powder of glass components, Mixing the phosphor material and the powder of glass components to create an initial mixture, Adding at least one oxidizing agent to the first mixture, Mixing the oxidizing agent with the first mixture to produce a second mixture, and Applying pressure and charge to the second mixture, thereby producing a glass composite wavelength converter. [2] Method according to claim 1, wherein the phosphor material is YAG:Ce. [3] Method according to claim 1, wherein the glass components have a glass transition temperature of less than approximately 600 °C. [4] Method according to claim 1, wherein the glass components have a glass transition temperature of less than approximately 400 °C. [5] Method according to claim 1, wherein the glass components comprise RO-B2O3-Al2O3-SiO2, and wherein R is selected from the group consisting of alkaline earth metals Mg, Ca, Sr and Ba. [6] Method according to claim 1, wherein the oxidizing agent is selected from the group consisting of NaNO3, KNO3, LiNO3, Na2SO3, K2SO3, LiSO3 and K2MnO4. [7] The method of claim 1, wherein the oxidizing agent is added in an amount of less than approximately 3 wt.%, based on an amount of the second mixture. [8] The method of claim 1, wherein the oxidizing agent is added in an amount of less than approximately 2 wt.%, based on an amount of the second mixture. [9] The method of claim 1, wherein the oxidizing agent is added in an amount of less than approximately 1 wt.%, based on an amount of the second mixture. [10] Method according to claim 1, wherein the phosphor material is YAG:Ce and the glass components comprise RO-B2O3-Al2O3-SiO2, and wherein R is selected from the group consisting of alkaline earth metals Mg, Ca, Sr and Ba. [11] Method according to claim 1, further comprising applying an inert atmosphere to the second mixture. [12] Method according to claim 1, wherein the pressure is at least approximately 30 MPa. [13] Method according to claim 1, wherein the glass composite wavelength converter has a quantum efficiency of at least approximately 80%. [14] Glass composite wavelength converter manufactured according to the method of claim 1. [15] Glass composite wavelength converter according to claim 14, wherein the phosphor material is YAG:Ce. [16] Glass composite wavelength converter according to claim 14, wherein the glass components comprise RO-B2O3-Al2O3-SiO2, and wherein R is selected from the group consisting of alkaline earth metals Mg, Ca, Sr and Ba. [17] Light source comprising: a light-emitting diode (LED) designed to emit a primary light; and a glass composite wavelength converter was manufactured according to the following procedure: provide at least one fluorescent material, providing a powder of glass components, Mixing the phosphor material and the powder of glass components to create an initial mixture, Adding at least one oxidizing agent to the first mixture, Mixing the oxidizing agent with the first mixture to produce a second mixture, and Applying pressure and charge to the second mixture, thereby producing a glass composite wavelength converter, wherein the phosphor material is designed to convert at least part of the primary light into secondary light. [18] Light source according to claim 17, wherein the phosphor material is YAG:Ce. [19] Light source according to claim 17, wherein the oxidizing agent is NaN03. [20] Light source according to claim 17, wherein the glass composite wavelength converter has a quantum efficiency of at least approximately 80%.