Annealing method

Abstract

The present invention provides a method for preparing a luminescent composition, the method comprising: (a) providing a first luminescent material or a precursor thereof, the first luminescent material being capable of emitting light in a first wavelength range; (b) providing a second luminescent material or a precursor thereof, the second luminescent material being capable of absorbing light in a second wavelength range and having an emission spectrum that at least partially overlaps with one or more excitation bands of the first luminescent material; and (c) mixing the first luminescent material or the precursor thereof with the second luminescent material or the precursor thereof, wherein the method further comprises: (I) preparing a mixture comprising (i) the first luminescent material or the precursor thereof and / or the second luminescent material or the precursor thereof and (ii) a salt; and (II) heating the mixture at a temperature of 300 °C or higher.

Description

Technical Field

[0001] The present invention relates to a method for preparing a luminescent composition. The present invention also relates to a method for preparing a luminescent material. The present invention also relates to luminescent compositions and materials obtainable by the method according to the present invention. The present invention also relates to devices comprising the luminescent composition and / or luminescent material of the present invention. Background Art

[0002] Luminescent down-conversion materials play an important role in solid-state lighting devices such as lighting and display applications.

[0003] WO2018 / 167266 discloses a composition comprising a luminescent material and a sensitizer material, wherein the luminescent material and the sensitizer material are selected such that the sensitizer material has an emission spectrum that at least partially overlaps with one or more excitation bands of the luminescent material, and wherein the luminescent material and the sensitizer material are arranged relative to each other to allow non-radiative energy transfer from the sensitizer material to the luminescent material. The application also describes a method for its preparation.

[0004] Non-radiative energy transfer from the sensitizer material to the luminescent material (sometimes also referred to as fluorescence resonance energy transfer, FRET) involves non-radiative energy transfer from excited sensitizer ions in the sensitizer material to acceptor (or emitter) ions in the luminescent material. This is manifested as an increase in the selective excitation of the sensitizer ions in the sensitizer material, resulting in an increase in the emission of the emitter ions in the luminescent material.

[0005] The present application discloses a further improved method for obtaining luminescent materials and compositions. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a method for preparing a luminescent composition, the method comprising:

[0007] (a) providing a first luminescent material or a precursor thereof, the first luminescent material being capable of emitting light in a first wavelength range;

[0008] (b) providing a second luminescent material or a precursor thereof, the second luminescent material being capable of absorbing light in a second wavelength range and having an emission spectrum that at least partially overlaps with one or more excitation bands of the first luminescent material; and

[0009] (c) mixing the first luminescent material or the precursor thereof with the second luminescent material or the precursor thereof,

[0010] wherein the method further comprises:

[0011] (I) preparing a mixture comprising (i) the first luminescent material or the precursor thereof and / or the second luminescent material or the precursor thereof and (ii) a salt; and

[0012] (II) Heat the mixture at 300 °C or higher temperature.

[0013] According to a second aspect of the present invention, there is provided a method for processing or obtaining a luminescent material, the method comprising:

[0014] (I) preparing a mixture comprising a luminescent material and / or its precursor and a salt, and

[0015] (II) heating the mixture at 300 °C or higher temperature,

[0016] wherein the ratio of the salt to the luminescent material and / or its precursor in the mixture is greater than 1:1 (w / w), preferably greater than 2:1 (w / w), more preferably greater than 5:1 (w / w), and most preferably greater than 10:1 (w / w).

[0017] The method according to the present invention can obtain a composition or material having excellent luminescence properties. More specifically, the method according to the first aspect of the present invention can arrange the luminescent material in a position close to the space to effectively control the inter-particle FRET. In addition, the method can obtain a composition or material having a small number of crystal defects and highly crystalline in a small size (about 50 nm or smaller, even about 20 nm or smaller). In addition, it has also been found that increasing the salt:luminescent material (w / w) ratio is beneficial to reducing sintering (aggregation, growth, and / or coalescence). This is particularly advantageous when the luminescent material is in the form of nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Shows the overlap of the emission spectrum (upper trace) of Lu3Al5O 12 :Ce(0.65%)(LuAG) as the second luminescent material with the excitation band (lower trace) of LaPO4:Tb as the first luminescent material.

[0019] Figure 2 Shows the overlap of the emission spectrum (upper trace) of Lu3Al5O 12 :Ce(0.65%)(LuAG) as the second luminescent material with the excitation band (lower trace) of Li3Ba2(La 0,6 Eu 0,4 )3(MoO4)8 as the first luminescent material.

[0020] Figure 3 Shows the photoluminescence spectra of YAG:Ce particles before and after salt treatment, heating, and desalting. The mixing was carried out at a 1:15 YAG:salt weight ratio. Samples were prepared as described in Example 3.

[0021] Figure 4 Shows YAG:Ce before annealing 3+Histogram of the particle size distribution of the particles.

[0022] Figure 5 Shows YAG:Ce obtained by a method without salt 3+ Histogram of the particle size distribution of the particles.

[0023] Figure 6 Shows YAG:Ce obtained by the method according to the present invention 3+ Histogram of the particle size distribution of the particles.

[0024] Figure 7 Shows YAG:Ce obtained by the method according to the present invention 3+ Histogram of the particle size distribution of the particles.

[0025] Figure 8 Shows YAG:Ce obtained by the method according to the present invention 3+ Histogram of the particle size distribution of the particles.

[0026] Figure 9 Shows YAG:Ce obtained by the method according to the present invention 3+ Histogram of the particle size distribution of the particles.

[0027] Figure 10 Shows the emission spectrum (upper trace) of YAG:Ce as the second luminescent material and the excitation band (lower trace) of YVPO4:Eu as the first luminescent material 3+ of the overlap. 3+ Detailed Description

[0028] Unless otherwise specified, the following detailed description applies to the method according to the first aspect of the present invention and the second aspect of the present invention.

[0029] Luminescent material or its precursor

[0030] The luminescent material or its precursor can be any suitable inorganic luminescent material or its precursor. Those skilled in the art will understand that, as used herein, the precursor refers to a material that is converted into a luminescent material under heating according to the present invention, such as an amorphous material.

[0031] The luminescent material or its precursor preferably contains optically active ions in a suitable host lattice. For example, the host lattice can be selected from: oxides, fluorides, nitrides, borates, garnets, molybdates, phosphates, vanadates, chlorides, sulfides, selenides, silicates, aluminates, fluorides, chlorides, nitrides, sulfoxides, selenoxides, fluorochlorides, fluorosilicates, and fluorobromides, or a combination thereof or another inorganic host material into which optically active ions can be introduced. For example, the luminescent material or its precursor can be any material referred to as the first luminescent material or the second luminescent material.

[0032] Preferably, the host lattice of the luminescent material or its precursor is garnet, more preferably selected from Y3Al5O 12 ("YAG") or Lu3Al5O 12 ("LuAG") or a combination thereof. Preferably, the luminescent material or its precursor is doped with one or more ions selected from Ce 3+ , Eu 3+ and Tb 3+ . More preferably, the luminescent material or its precursor is doped with a dopant that at least includes Ce 3+ , optionally in combination with Tb 3+ . Most preferably, the host lattice is selected from Y3Al5O 12 ("YAG") or Lu3Al5O 12 ("LuAG") or a combination thereof, and the dopant includes Ce 3+ , optionally in combination with Tb 3+ .

[0033] Preferably, the luminescent material or its precursor is in the form of particles, more preferably in the form of nanoparticles. Suitable nanoparticles include particles that are nanoscale in at least one dimension, preferably <100 nm. Those skilled in the art will understand that the nanoparticles can be, for example, in the form of nanosheets, nanorods or nanodots. Nanoparticles are particularly suitable for the method of the present invention.

[0034] Preferably, as measured using a transmission electron microscope (TEM), the D 50 value of the minimum size of the nanoparticles is ≥1 nm and ≤100 nm, more preferably ≥1 nm and ≤50 nm, most preferably ≥2 nm and ≤10 nm. D 50 is defined as the median of the length of the minimum size of the nanoparticles, measured from a collection of at least 50 representative particles.

[0035] The nanoparticles can contain organic ligands. As is known to those skilled in the art, these are commonly referred to as capping molecules (or capping agents) and are used to control the growth and / or coalescence of the particles.

[0036] The ligand can be any organic ligand suitable for this purpose. Examples of ligands include fatty acids (including their salts and esters), amines, polyols, such as oleic acid, oleylamine, oleate, tributylamine, and (poly)ethylene glycol.

[0037] Preferably, the ligands of the nanoparticles are adjusted to enhance mixing with the salt. Generally, heating to a high temperature (about 300 °C or higher) will cause the organic ligands of the particles to be removed. In a preferred embodiment, a temperature of about 500 °C or higher is used. A temperature of 500 °C or higher can achieve higher efficacy.

[0038] The first luminescent material and its precursor, and the second luminescent material and its precursor

[0039] The method according to the first aspect of the present invention comprises providing a first luminescent material or its precursor and a second luminescent material or its precursor.

[0040] The first luminescent material is capable of emitting light in a first wavelength range. Those skilled in the art will understand that the first luminescent material is used as a luminescent material in the composition obtained or obtainable by the method according to the present invention. The first wavelength range can be any target wavelength range. Preferred wavelength ranges will be described below.

[0041] The second luminescent material is capable of absorbing light in a second wavelength range. Those skilled in the art will understand that the second luminescent material is used as a sensitizer material according to the present invention. The second wavelength range can be any target wavelength range. Preferred wavelength ranges will be described below.

[0042] The second luminescent material has an emission spectrum that at least partially overlaps with one or more excitation bands of the first luminescent material. Specifically, when excited by light in the second wavelength range, the second luminescent material has an emission spectrum that at least partially overlaps with one or more excitation bands of the first luminescent material. Those skilled in the art can well determine the overlap of the spectra based on the spectra known in the art or by determining the spectra through routine experiments.

[0043] For example, Figure 1 shows the overlap of the emission spectrum (upper trace) of Lu3Al5O 12 :Ce(0.65%)(LuAG) as the second luminescent material with the excitation band (lower trace) of LaPO4:Tb as the first luminescent material. The overlapping region is indicated by a dashed line. Figure 2 shows the overlap of the emission spectrum (upper trace) of Lu3Al5O 12 :Ce(0.65%)(LuAG) as the second luminescent material with the excitation band (lower trace) of Li3Ba2(La 0.6 Eu 0.4 )3(MoO4)8 as the first luminescent material. The overlapping region is also indicated by a dashed line.

[0044] The first luminescent material

[0045] Any suitable inorganic luminescent material can be used as the first luminescent material. For example, luminescent materials known in the art can be used. The first luminescent material is capable of emitting light in a first wavelength range. The first wavelength range can be any target wavelength range.

[0046] Preferably, the first luminescent material comprises a red luminescent material. As used herein, the term red luminescent material refers to a material having one or more emission bands between 600 nm and 700 nm upon appropriate excitation. For color rendering purposes, it may be desirable to provide a red luminescent material. According to an alternative aspect of the present invention, the first luminescent material is a material having one or more emission bands between 700 and 1400 nm (IR-A), between 580 and 600 nm (amber and / or orange), between 560 and 580 nm (yellow), between 510 and 560 nm (green), between 480 and 510 nm (cyan), between 440 - 480 nm (blue), between 400 - 440 nm (violet), between 315 - 400 nm (UV-A) and / or between 280 - 315 nm (UV-B).

[0047] In a preferred embodiment, the first luminescent material comprises a rare earth doped phosphor material. The phosphor material can be a divalent or trivalent rare earth doped phosphor. Examples of suitable rare earth doped phosphor materials include, but are not limited to: LaPO4:Tb 3 + 、CaAlSiN3:Eu 2+ 、Y2O3:Eu 3+ 、Y(V,P)O4:Eu 3+ 、Y3Al5O 12 :Ce 3+ 。

[0048] The phosphor material can be purchased on the open market today or synthesized, for example, as described in [iwotzki, K.; Meyssamy, H.; Kornowski, A.; Haase, M. J. Phys. Chem. B. 2000, 104, 2824 - 2828].

[0049] As is known to those skilled in the art, rare earth doped phosphor materials comprise a host lattice doped with optically active ions.

[0050] The first luminescent material can have any suitable host lattice. For example, the host lattice can be selected from: oxides, fluorides, nitrides, borates, garnets, molybdates, phosphates, vanadates, chlorides, sulfides, selenides, silicates, aluminates, fluorides, chlorides, oxynitrides, sulfur oxides, selenium oxides, fluorochlorides, fluorosilicates, and fluorobromides, or a combination thereof or another inorganic host material into which optically active ions can be introduced. For example, the luminescent material or its precursor can be any material referred to as the first luminescent material or the second luminescent material.

[0051] Preferably, the host lattice of the first luminescent material is an oxide, phosphate, vanadate, or a combination thereof, more preferably selected from Y3Al5O 12 ("YAG"), Lu3Al5O 12 ("LuAG"), Y2O3, YVPO4, YVO4, or LaPO4, or a combination thereof. Preferably, the preferred host lattice of the first luminescent material is doped with one or more ions selected from Eu 3+ , Ce 3+ , Tb 3+ , and Mn 4+ . These ions provide good emission characteristics, such as strong emission bands and / or the red part of the visible spectrum.

[0052] In the case of Eu 3+ doping, the first luminescent material may, for example, have a host lattice with a doping level of 2-100% Eu 3+ , more preferably 5-50% Eu 3+ . In the case of Tb 3+ doping, the first luminescent material may, for example, have a host lattice with a doping level of 5-100% Tb 3+ , more preferably 20-50% Tb 3+ . In the case of Mn 4+ doping, the first luminescent material may, for example, have a host lattice with a doping level of 0.1-20%, most preferably between 1-5%. In the case of Ce 3+ doping, the first luminescent material may, for example, have a host lattice with a doping level of 0.05-5%, more preferably 0.1-4%.

[0053] In an exemplary embodiment, the first luminescent material is selected from: (Ca,Sr)Ga2O6:Eu 3+ (and / or Tb 3+ ), (Ca,Sr,Ba)La2Bi2(SiO4)3O:Eu 3+ (and / or Tb 3+ ), (Ca,Sr,Ba)SnO3:Eu 3+ (and / or Tb 3+ ), (Ca,Y,Gd)MoO4:Eu 3+ (and / or Tb 3+ ), (Y,Gd)BO3 (pseudo-vaterite):Eu 3+ (and / or Tb 3+ ), (Y,Tb)SiO5:Eu 3+ (and / or Tb 3+ ), A-La2O3:Eu 3+ (and / or Tb 3+ ), Ba2(SiO4):O2- : EU 3+ (and / or Tb 3+ )、Ba2MgSi2O7:Eu 3+ (and / or Tb 3+ )、Ba2Y(BO3)2CL:EU 3+ (and / or Tb 3+ )、Ba3(PO4)2:Eu 3+ (and / or Tb 3+ )、Ba3Ca3(PO4)4:Eu 3+ (and / or Tb 3+ )、Ba3Gd(BO3)3:Eu 3+ (and / or Tb 3+ )、Ba3Gd2(BO3)4:Eu 3+ (and / or Tb 3+ )、Ba3La2(BO3)4:Eu 3+ (and / or Tb 3+ )、Ba3V2O8:Eu 3+ (and / or Tb 3+ )、Ba3Y2(BO3)4:Eu 3+ (and / or Tb 3+ )、BaB8O 13 :Eu 3+ (and / or Tb 3+ )、BaBPO5:Eu 3+ (and / or Tb 3+ )、BaFCl:Eu 3+ (and / or Tb 3+ )、BaGd2O4:Eu 3+ (and / or Tb 3+ )、BaGd4Si5O 17 :Sm:Eu 3+ (and / or Tb 3+ )、BaGdB9O 16 :Eu 3+ (and / or Tb 3+ )、BaLaB9O 16 :Eu 3+ (and / or Tb 3+ )、BaSO4:Eu 3+ (and / or Tb 3+ )、BaY2F8:Yb:Eu 3+ (and / or Tb 3+ )BaY2Si3O 10 :Eu 3+ (and / or Tb 3+ )、BaYB9O 16:Eu 3+ (and / or Tb 3+ ), BaZr(BO3)2:Eu 3+ (and / or Tb 3+ ), BaZrO3:Eu 3+ (and / or Tb 3+ ), BaZrO3:Eu 3+ (and / or Tb 3+ ), b-BaB2O4:Eu 3+ (and / or Tb 3+ ), B-Gd2O3:Eu 3+ (and / or Tb 3+ ), Ca2Al(AlSiO7):Eu 3+ (and / or Tb 3 + ), Ca2Gd2(GeO4)2O:Eu 3+ (and / or Tb 3+ ), Ca2Gd8(SiO4)6O2:Eu 3+ (and / or Tb 3+ ), Ca2Gd8Si6O 26 :Eu 3+ (and / or Tb 3+ ), Ca2La8(SiO4)6O2:Eu 3+ (and / or Tb 3+ ), Ca3(BO3)2:Eu 3+ (and / or Tb 3+ ), Ca3Al2O6:Eu 3+ (and / or Tb 3+ ), Ca3Gd2(BO3)4:Eu 3+ (and / or Tb 3+ ), Ca3La2(BO3)4:Eu 3+ (and / or Tb 3+ ), Ca3Y2(BO3)4:Eu 3 + (and / or Tb 3+ ), Ca4GdO(BO3)3:Eu 3+ (and / or Tb 3+ ), Ca5(PO 11 )3F:Eu 3+ (and / or Tb 3+ ), Ca5(PO4)3Br:Eu 3+ (and / or Tb 3+ ), Ca5(PO4)3F:(4f-site):Eu 3+ (and / or Tb 3+)、Ca5(PO4)3F:(6h-site):Eu 3+ (and / or Tb 3+ )、Ca5(PO4)3OH:Eu 3+ (and / or Tb 3+ )、CaBPO5:Eu 3+ (and / or Tb 3+ )、CaF2:Eu 3+ (and / or Tb 3+ )、CaLaB7O 13 :Eu 3+ (and / or Tb 3+ )、Calcite - CaCO3:Eu 3+ (and / or Tb 3+ )、CaO:Eu 3+ (and / or Tb 3+ )、CaSO4:Eu 3+ (and / or Tb 3+ )、CaYO(BO3):Eu 3+ (and / or Tb 3+ )、C - Gd2O3:Eu 3+ (and / or Tb 3+ )、C - Lu2O3:(C2):Eu 3+ (and / or Tb 3+ )、C - Lu2O3:(C3i):Eu 3+ (and / or Tb 3+ )、Cs2NaYF6:Tm:Eu 3+ (and / or Tb 3+ )、C - Sc2O3:Yb:Eu 3+ (and / or Tb 3+ )、C - Y2O3:Eu 3+ (and / or Tb 3+ )、EU 3+ (and / or Tb 3+ )、[(ttfa)3(phen)]:Eu 3+ (and / or Tb 3+ )、Gd 17.33 (BO3)4(B2O5)2O 16 :Eu 3+ (and / or Tb 3+ )、Gd2BaZnO5:Eu 3+ (and / or Tb 3+ )、Gd2O2(SO4):Eu 3+ (and / or Tb 3+ )、Gd2P4O 13 :Eu 3+(and / or Tb 3+ ), Gd3O4Br:Eu 3+ (and / or Tb 3+ ), Gd3PO7:Eu 3+ (and / or Tb 3+ ), Gd3Te2Li3O 12 :Eu 3+ (and / or Tb 3+ ), Gd8P2O 17 :Eu 3+ (and / or Tb 3+ ), GdA 13 (BO3)4:Eu 3+ (and / or Tb 3+ ), GdAlO3:Eu 3+ (and / or Tb 3+ ), GdA1O3:Eu 3+ (and / or Tb 3+ ), GdB3O6:Eu 3+ (and / or Tb 3+ ), GdBO3:Eu 3+ (and / or Tb 3+ ), GdGaO3:Eu 3+ (and / or Tb 3+ ), GdOBr:Eu 3+ (and / or Tb 3+ ), GdOCl:Eu 3+ (and / or Tb 3+ ), GdP3O9:Eu 3+ (and / or Tb 3+ ), GdPO4:Eu 3+ (and / or Tb 3+ ), I-CaB2O4:Eu 3+ (and / or Tb 3+ ), InBO3:Eu 3+ (and / or Tb 3 + ), I-SrB2O4:Eu 3+ (and / or Tb 3+ ), KCaGd(PO4)2:Eu 3+ (and / or Tb 3+ ), La 26 O 27 (BO3)8:Eu 3+ (and / or Tb 3 + ), La2BaZnO5:Eu 3+ (and / or Tb 3+ ), La2Hf2O7:Eu3+ (and / or Tb 3+ ), La2O2(SO4):Eu 3+ (and / or Tb 3+ ), La2O2S:Eu 3+ (and / or Tb 3+ ), La2W3O 12 :Eu 3+ (and / or Tb 3+ ), La2Zr3(MoO4)9:Eu 3+ (and / or Tb 3+ ), La3TaO4Cl6:Eu 3+ (and / or Tb 3+ ), La3WO6C13:Eu 3+ (and / or Tb 3+ ), LaA1O3:Eu 3+ (and / or Tb 3+ ), LaB3O6:Eu 3+ (and / or Tb 3+ ), LaBO3:Eu 3+ (and / or Tb 3+ ), LaF3:Eu 3+ (and / or Tb 3+ ), LaGaO3:Eu 3+ (and / or Tb 3+ ), LaMgB5O 10 :Eu 3+ (and / or Tb 3+ ), LaOBr:Eu 3+ (and / or Tb 3+ ), LaOCl:Eu 3+ (and / or Tb 3+ ), LaOF:Eu 3+ (and / or Tb 3+ ), LaOI:Eu 3+ (and / or Tb 3+ ), LaP3O9:Eu 3+ (and / or Tb 3+ ), LaPO4:Eu 3+ (and / or Tb 3+ ), LaYO3:Eu 3+ (and / or Tb 3+ ), Li2Lu5O4(BO3)3:Eu 3+ (and / or Tb 3+ ), Li3Ba2La3(MoO4)8:Eu 3+ (and / or Tb 3+)、Li3La2(BO3)3:Eu 3+ (and / or Tb 3+ )、Li6Gd(BO3)3:Eu 3+ (and / or Tb 3+ )、Li6Y(BO3)3:Eu 3+ (and / or Tb 3+ )、LiCaAlF6:Eu 3+ (and / or Tb 3+ )、LiEu 3+ (and / or Tb 3+ )、Mo2O8:Eu 3+ (and / or Tb 3+ )、LiGd6O5(BO3)3:Eu 3+ (and / or Tb 3+ )、LiGdF4:Eu 3+ (and / or Tb 3+ )、LiGdGeO4:Eu 3+ (and / or Tb 3+ )、LiGdO2:Eu 3+ (and / or Tb 3+ )、LiGdSiO4:Eu 3+ (and / or Tb 3+ )、LiLa2O2BO3:Eu 3+ (and / or Tb 3+ )、LiLaGeO4:Eu 3+ (and / or Tb 3+ )、LiLaO2:Eu 3+ (and / or Tb 3+ )、LiLaP4O 12 :Eu 3+ (and / or Tb 3+ )、LiLaSiO4:Eu 3+ (and / or Tb 3+ )、LiLuGeO4:Eu 3+ (and / or Tb 3+ )、LiLuO2:Eu 3+ (and / or Tb 3+ )、LiLuSiO4:Eu 3+ (and / or Tb 3+ )、LiScO2:Eu 3+ (and / or Tb 3+ )、LiSr2YO4:Eu 3+ (and / or Tb 3+ )、LiSrAlF6:Eu 3+ (and / or Tb 3+)、LiY6O5(BO3)3:Eu 3+ (and / or Tb 3 + )、LiYF4:Eu 3+ (and / or Tb 3+ )、LiYGeO4:Eu 3+ (and / or Tb 3+ )、LiYO2:Eu 3+ (and / or Tb 3+ )、LiYSiO4:Eu 3+ (and / or Tb 3+ )、Lu2O2(SO4):Eu 3+ (and / or Tb 3+ )、Lu2Si2O7:Eu 3+ (and / or Tb 3+ )、Lu3A15O 12 :Eu 3+ (and / or Tb 3+ )、Lu3Al5O 12 :Yb:Eu 3+ (and / or Tb 3+ )、LuBO3:Eu 3+ (and / or Tb 3+ )、LuBO3(calcite):Eu 3+ (and / or Tb 3+ )、LUOCl:EU 3+ (and / or Tb 3+ )、LuPO4:Eu 3+ (and / or Tb 3+ )、Mg2Gd8(SiO4)6O2:Eu 3+ (and / or Tb 3+ )、Mg2La8(SiO4)6O2:Eu 3+ (and / or Tb 3+ )、MgO:Eu 3+ (and / or Tb 3+ )、MgSiO3:Eu 3+ (and / or Tb 3+ )、Na3YSi3O9:Eu 3+ (and / or Tb 3+ )、Na6Gd(BO3)3:Eu 3+ (and / or Tb 3+ )、NaGdGeO4:Eu 3+ (and / or Tb 3+ )、NaGdO2:Eu 3+ (and / or Tb 3+)、NaGdSiO4:Eu 3+ (and / or Tb 3+ )、NaLaGeO4:Eu 3+ (and / or Tb 3+ )、NaLaO2:Eu 3 + (and / or Tb 3+ )、NaLaSiO4:Eu 3+ (and / or Tb 3+ )、NaLuGeO4:Eu 3+ (and / or Tb 3+ )、NaLuSiO4:Eu 3+ (and / or Tb 3+ )、NaScO2:Eu 3+ (and / or Tb 3+ )、NaSrLa(VO4)2:Eu 3+ (and / or Tb 3+ )、NaYGeO4:Eu 3+ (and / or Tb 3+ )、NaYSiO4:Eu 3+ (and / or Tb 3+ )、ScBO3:Eu 3+ (and / or Tb 3+ )、S C OC1:Eu 3+ (and / or Tb 3+ )、ScPO4:Eu 3+ (and / or Tb 3+ )、Sr2B5O5:Eu 3+ (and / or Tb 3+ )、Sr2Gd8(SiO4)6O2:Eu 3+ (and / or Tb 3+ )、Sr2La2Zn2O7:Eu 3+ (and / or Tb 3+ )、Sr2La2Zn2O7:Eu 3+ (and / or Tb 3+ )、Sr2LaA1O5:Eu 3+ (and / or Tb 3+ )、Sr3(BO3)2:Eu 3+ (and / or Tb 3+ )、Sr3(PO4)2:Eu 3+ (and / or Tb 3+ )、Sr3(PO4)2:Sm:Eu 3+ (and / or Tb 3+ )、Sr3Gd2(BO3)4:Eu3+ (and / or Tb 3+ ), Sr3La2(BO3)4:Eu 3+ (and / or Tb 3+ ), Sr3La6(SiO4)6:Eu 3+ (and / or Tb 3+ ), Sr3Y2(BO3)4:Eu 3+ (and / or Tb 3+ ), Sr5(PO4)3F:Eu 3+ (and / or Tb 3+ ), Sr9Ln(VO4)7:Eu 3+ (and / or Tb 3+ ), SrAl2B2O7:Eu 3+ (and / or Tb 3+ ), SrB4O7:Eu 3+ (and / or Tb 3+ ), SrB6O 10 :Eu 3+ (and / or Tb 3+ ), SrCO3:Eu 3+ (and / or Tb 3+ ), SrGdA1O4:Eu 3+ (and / or Tb 3+ ), SrHfO3:Eu 3+ (and / or Tb 3+ ), SrLa2BeO5:Eu 3+ (and / or Tb 3+ ), SrLa2BeO5:Eu 3+ (and / or Tb 3+ ), SrLaA1O4:Eu 3+ (and / or Tb 3+ ), SrLaGa3O7:Eu 3+ (and / or Tb 3+ ), SrLaO(BO3):Eu 3+ (and / or Tb 3 + ), SrO:Eu 3+ (and / or Tb 3+ ), SrY2O4:(Sr-site):Eu 3+ (and / or Tb 3+ ), SrY2O4:Eu 3+ (and / or Tb 3+ ), SrY2O4:Eub 3+ (and / or Tb 3+ ), Tb2Mo3O 12 :Eu3+ (and / or Tb 3+ ), Tb2W3O 12 :Eu 3+ (and / or Tb 3+ )、TbBO3:Eu 3+ (and / or Tb 3+ ), ThO2:Eu 3+ (and / or Tb 3+ )、Gd2SiO5:Eu 3+ (and / or Tb 3+ )、Y2SiO5:Eu 3+ (and / or Tb 3+ ), Y 17.33 (BO3)4(B2O5)2O l6 :Eu 3+ (and / or Tb 3+ )、Y2Ge2O7:Eu 3+ (and / or Tb 3+ )、Y2GeO5:Eu 3+ (and / or Tb 3+ )、Y2O2(SO4):Eu 3+ (and / or Tb 3+ )、Y2O2S:Eu 3+ (and / or Tb 3+ )、Y2O2S:Eu 3+ (and / or Tb 3+ )、Y2O3:Eu 3+ (and / or Tb 3+ ), Y2P4O 13 :Eu 3+ (and / or Tb 3+ )、Y2Si2O7:Eu 3+ (and / or Tb 3+ )、Y2SiO5:Eu 3+ (and / or Tb 3+ ), Y3Al5O 12 :Eu 3+ (and / or Tb 3+ )、Y3O4Br:Eu 3+ (and / or Tb 3+ )、Y3O4CI:Eu 3+ (and / or Tb 3+ )、Y3PO7:Eu 3+ (and / or Tb 3+ )、Y4GeO8:Eu 3+ (and / or Tb 3+ ), Y8P2O 17 :Eu3+ (and / or Tb 3+ ), YAl3(BO3)4:Eu 3+ (and / or Tb 3+ ), YAlO3:Eu 3+ (and / or Tb 3+ ), YBO3:Eu 3+ (and / or Tb 3+ ), YbOBr:Yb:Eu 3+ (and / or Tb 3+ ), YF3:Eu 3+ (and / or Tb 3+ ), YOBr:Eu 3+ (and / or Tb 3+ ), YOCl:Eu 3+ (and / or Tb 3+ ), YOCl:Eu 3+ (and / or Tb 3+ ), YOF:Eu 3+ (and / or Tb 3+ ), YOF:Eu 3+ (and / or Tb 3+ ), YP3O9:Eub 3+ (and / or Tb 3+ ), YPO4:Eub 3+ (and / or Tbb 3+ ), YTaO4:Eub 3+ (and / or Tb 3+ ), YVO4:Eub 3+ (and / or Tbb 3+ ), ZrP2O7:Eu 3+ (and / or Tb 3+ ), Y3Al5O 12 :Ce 3+ , Lu3Al5O 12 :Ceb 3+ , K2SiF6:Mn 4+ or a mixture thereof.

[0054] Those skilled in the art will understand that the symbol: Eu 3+ (or Tb 3+ or Ce 3+ or Mn 4+ ) indicates that the host lattice is doped with Eu 3+ or Tb 3+ , or Ce 3+ or Mn 4+ .

[0055] The second luminescent material

[0056] Any suitable inorganic luminescent material can be used as the second luminescent material. The second material is capable of absorbing light within a second wavelength range. The second wavelength can be any target wavelength range.

[0057] Preferably, the second luminescent material can be excited within a wavelength range of 380 to 580 nm. Preferably, the second luminescent material is within the UV-A (315 to 400 nm), violet (400 to 440 nm), blue (440 to 480 nm), or green (510 to 560 nm) wavelength ranges, and most preferably can be excited within the blue (440 to 480 nm) wavelength range. LEDs based on (Al, In, Ga)N provide efficient "pump" light generation within the ultraviolet to blue wavelength range (from about 400 nm to about 480 nm). Examples of blue-excitable materials are CaAlSiN3:Eu 2+ 、Y3Al5O 12 :Ce 3+ 、CsPbBr3.

[0058] In other aspects of the present invention, the second luminescent material is a material having one or more excitation bands between 700 and 1400 nm (IR-A), between 580 and 600 nm (amber and / or orange), between 560 and 580 nm (yellow), between 510 - 560 nm (green), between 480 and 510 nm (cyan), between 440 and 480 nm (blue), between 400 - 440 nm (violet), between 315 - 400 nm (UV-A), and / or between 280 - 315 nm (UV-B).

[0059] Preferably, the host lattice of the second luminescent material is garnet, fluoride, silicate, phosphate, or nitride, and more preferably selected from Y3Al5O 12 ("YAG"), Lu3Al5O 12 ("LuAG"), MgF2, CaF2, Sr2SiO4, Ba2SiO4, Ca2MgSi2O7, LiSrPO4, CaAlSiN3, or a combination thereof. Preferably, the preferred host lattice of the second luminescent material is doped with one or more ions selected from EU 2+ 、Pb 2 + 、Bi 3+ and Ce 3+ , more preferably EU 2+ or Ce 3+ , and most preferably Ce 3+ .

[0060] Preferably, the host lattice of the second luminescent material or its precursor is garnet, such as Y3Al5O 12 ("YAG") or Lu3Al5O12 (“LuAG”) or a combination thereof. Most preferably, the host lattice is selected from Y3Al5O 12 (“YAG”) or Lu3Al5O 12 (“LuAG”) or a combination thereof, and the dopant includes Ce 3+ , optionally in combination with Tb 3+ .

[0061] Preferably, in the case of Ce 3+ doping, the second luminescent material has a host lattice with a doping level of 0.05 - 5%, more preferably 0.1 - 4%.

[0062] Preferably, the first luminescent material and / or the second luminescent material is in the form of nanoparticles. Suitable nanoparticles include particles with at least one dimension in the nanoscale, preferably <100 nm. This small size allows for a smaller distance between the surfaces of the first and second materials, which (further) enables non-radiative energy transfer between the particles to occur.

[0063] More preferably, the first luminescent material and the second luminescent material are in the form of nanoparticles. Providing both materials in the form of nanoparticles allows for more efficient mixing and uniform distribution of the particles, which further promotes the occurrence of non-radiative energy transfer between the particles.

[0064] As previously discussed, as measured using a transmission electron microscope (TEM), the D 50 value of the minimum size of the nanoparticles is preferably ≥1 nm and ≤100 nm, more preferably ≥1 nm and ≤50 nm, and most preferably ≥2 nm and ≤10 nm. D 50 is defined as the median of the length of the minimum size of the nanoparticles, measured from a set of at least 50 representative particles.

[0065] In another preferred embodiment, the second luminescent material is provided as a bulk material, and the first luminescent material is provided on the second luminescent material. In this case, the term “bulk” particularly means and / or includes greater than the nanoscale, for example, with a diameter greater than 100 nm, and includes the micron scale.

[0066] salt

[0067] Any suitable salt with a melting temperature higher than the heating temperature of the mixture can be used in the methods according to all aspects of the present invention.

[0068] Preferably, the salt contains Se 2- , S 2- , Cl - , F - , Br - , I - , SO4 2- , PO4 3- or NO3- or a combination thereof as an anion, and H + , Li + , Na + , K + , Be 2+ , Ca 2+ , Al 3+ , Ba 2+ , Mg 2+ , or Sr 2+ or a combination thereof as a cation. More preferably, the salt is K2SO4 (T m = 1069 °C).

[0069] The salt is preferably provided in the form of a crystalline solid.

[0070] If desired, the salt can be milled or ground before mixing. Smaller particles allow for more uniform mixing of the salt with the luminescent material.

[0071] (I) Prepare a mixture comprising a luminescent material or a precursor thereof and a salt.

[0072] The methods according to all aspects of the present invention include preparing a mixture comprising a luminescent material or a precursor thereof and a salt. Thus, those skilled in the art will understand that the properties and features described herein apply to the first and second aspects of the present invention. Thus, the (preferred) properties and features described with respect to "a mixture comprising (i) a first luminescent material or a precursor thereof and (ii) a salt" apply to "a mixture comprising (i) a first luminescent material or a precursor thereof and / or a second luminescent material or a precursor thereof and (ii) a salt", with the necessary modifications.

[0073] A mixture comprising a luminescent material or a precursor thereof and a salt can be prepared in any suitable manner.

[0074] In a preferred embodiment (hereinafter also referred to as A), preparing the mixture comprises dry mixing (i) a luminescent material or a precursor thereof and (ii) a salt. Those skilled in the art will understand that in this embodiment, the luminescent material or a precursor thereof and the salt are mixed as dry solids. The advantage of this embodiment is that no suspension, dispersion, and / or evaporation steps are required. Preferably, the dry mixing comprises milling or grinding a mixture comprising (i) a luminescent material or a precursor thereof and (ii) a salt.

[0075] In another preferred embodiment (hereinafter also referred to as B), preparing the mixture comprises mixing (i) the luminescent material or a precursor thereof and (ii) the salt into a liquid to obtain a dispersion. The liquid can then be separated from the dispersion, preferably by evaporating the liquid. The salt can be added to the liquid before, after, or simultaneously with dispersing the luminescent material in the liquid. Preferably, an excess of the salt is added so that it does not completely dissolve.

[0076] Any suitable liquid can be selected in which the luminescent material, preferably in particulate form, most preferably in the form of nanoparticles, can be well dispersed. Preferably, the liquid has a relatively low boiling point as this aids in removing the liquid at a later stage of the process. Preferably, the liquid is water or an alcohol. Preferably, the alcohol is a C1-C4 alkanol such as methanol, ethanol or propanol.

[0077] Preferably, the mixture is sonicated in an ultrasonic bath or using an ultrasonic probe. The advantage of doing this is that mixing can be enhanced.

[0078] In another preferred embodiment (also referred to hereinafter as C), preparing the mixture comprises preparing an emulsion comprising a dispersed phase and a continuous phase, the dispersed phase comprising (i) a luminescent material or a precursor thereof and (ii) a salt. The liquid forming the emulsion can then be separated from the emulsion, preferably by sedimentation of the emulsion droplets. Preferably, the dispersed phase is an aqueous phase and the continuous phase is a non-polar (or oil) phase. Any suitable non-polar solvent can be used to obtain the non-polar (or oil) phase, such as a C5-C 12 alkane, preferably cyclohexane.

[0079] The emulsion can be prepared in any suitable manner, such as using sonication. The sedimentation can be carried out in any suitable manner, such as by contacting the emulsion with ethanol or acetone and / or by gravity separation (such as centrifugation).

[0080] Preferably, preparing the mixture comprising (i) the luminescent material or a precursor thereof and (ii) the salt comprises (applicable to each of embodiments A, B and C) comminuting the salt, such as by grinding or milling and / or subjecting (i) the luminescent material or a precursor thereof and / or (ii) the salt to sonication, grinding and / or milling. These measures can be carried out on the materials before, during or after mixing.

[0081] Salt:luminescent material weight ratio (w / w)

[0082] There is no specific upper or lower limit to the weight ratio of salt to luminescent material. Preferably, a sufficiently high salt:luminescent (w / w) ratio is selected such that the (nano)particles of the luminescent material or a precursor thereof are separated far enough to prevent sintering at high temperatures. As previously discussed, it has been found that increasing the salt:luminescent (w / w) ratio is beneficial for reducing sintering (aggregation, growth and / or coalescence). In the case of embodiments (A) and (B) described above, this effect has been found to be particularly significant.

[0083] Preferably, the weight ratio of the salt to the luminescent material and / or its precursor in the mixture is greater than 1:1 (w / w), preferably greater than 2:1 (w / w), more preferably greater than 5:1 (w / w), and most preferably greater than 10:1 (w / w). Preferably, the ratio of the salt to the luminescent material in the mixture is about 50:1 or higher, about 100:1 or higher, or 200:1 or higher, especially in the case of the embodiments (A) or (B) described above. It has been found that a higher weight ratio of the salt to the luminescent substance can result in better separation of the luminescent material and better salt matrix properties. It has further been found that a higher salt:luminescent material ratio allows the mixture to be heated for a longer time without sintering the nanoparticles.

[0084] However, an extremely high salt:luminescent material ratio may be impractical and require an extremely large amount of salt. Therefore, for practical reasons, the ratio is preferably about 500:1 or lower, more preferably about 100:1 or lower. In the case of using the mixing method (C), the preferred salt:luminescent material ratio may be lower. Preferably, 10:1 or lower is used, more preferably 5:1 or lower.

[0085] As used herein, all ratios refer to weight ratios. As will be understood by those skilled in the art, and as used herein when expressing ratios, the weight of the luminescent material refers to the total weight of the luminescent material (including the first luminescent material and the second luminescent material, if both are present, including the ligand, if present) and its precursor present in the mixture.

[0086] (II) Heating the mixture at a temperature of 300 °C or higher.

[0087] The methods according to all aspects of the present invention include heating the mixture at a temperature of 300 °C or higher. Therefore, those skilled in the art will understand that the (preferred) characteristics and features described herein apply, mutatis mutandis, to the first and second aspects of the present invention.

[0088] It has been found that heating the luminescent material causes an increase in the crystallinity of the material, with fewer defects. In the case of a doped crystalline luminescent material, heating the luminescent material can further promote the migration of the doped ions into the host lattice, thereby enhancing the emission. Finally, the heat treatment can remove any organic surface ligands or other unwanted organic materials present.

[0089] It has been found that higher temperatures may give better results. Preferably, the temperature is about 500 °C or higher, more preferably about 800 °C or higher, and even more preferably 1000 °C or higher.

[0090] There is no specific upper limit to the temperature at which the mixture is heated, and the heating can be carried out at any suitable temperature below the melting temperature of the salt and below the melting and / or decomposition temperature of the luminescent material. The melting temperature of the salt is known and can be determined by a person skilled in the art. For practical reasons, a temperature of about 1500 °C or lower, more preferably 1300 °C or lower, can be preferably used. In a preferred embodiment, the mixture is heated at a temperature of 900 to 1500 °C, preferably for 1 minute to 20 hours.

[0091] When higher temperatures are used, a higher salt:luminescent material ratio can be advantageously used to further limit the aggregation of the luminescent material.

[0092] Preferably, the mixture is heated for at least 1 minute, more preferably for 15 minutes to 12 hours. It has been found that when using higher temperatures, good results can be obtained with shorter times.

[0093] It has further been found that a high salt:luminescent material ratio allows for longer heating times without causing aggregation of the luminescent material.

[0094] Preferably, the mixture is heated in an inert atmosphere (such as N2 or Ar gas). However, in other embodiments according to the present invention, an oxidizing or reducing gas may be required to form the luminescent material from the precursor or to keep the active ions in or at the desired oxidation state.

[0095] Separation of the luminescent material

[0096] Generally, after heat treatment, the luminescent material is separated from the mixture. The salt can be removed from the mixture by any suitable means, such as by contacting the liquid with a solvent that can dissolve the salt, preferably water. In a preferred embodiment, the salt is K2SO4 and the solvent is water.

[0097] Removal of organic ligands

[0098] Preferably, organic ligands (if present) are removed from the nanoparticles. It has been found that removing organic ligands is beneficial for bringing different types of luminescent materials into close proximity, which is particularly advantageous if a composition that allows for interparticle energy transfer (FRET) between the nanophosphors is desired.

[0099] Methods for removing organic ligands from luminescent materials are known in the art, and the optional removal of organic ligands is not limited to a particular method. For example, organic ligand removal can be achieved by contacting nanoparticles containing the organic ligand with an acid such as HCl. The use of HCl for removing organic ligands is described in Wang et al., "Regulating upconversion through energy migration in core-shell nanoparticles", Supplementary Information, Nature Materials (2011) 1-35. Another method is described in NanoLett., 2011, 11(12), pages 5356-5361. Another method involves contacting the nanophosphor with an oxidizing agent.

[0100] In a preferred embodiment, the organic ligand is removed by heat treatment to prevent damage to the nanoparticles.

[0101] It is generally found that treatment of the luminescent material by using the method according to the present invention can remove the organic ligand.

[0102] (c) Mix a first luminescent material or its precursor with a second luminescent material or its precursor.

[0103] The first luminescent material or its precursor and the second luminescent material or its precursor can be mixed in a liquid or using dry materials by any method known in the art, such as milling, grinding, stirring, etc.

[0104] In a preferred embodiment, at least one of the first luminescent material and the second luminescent material is provided as a dispersion in a liquid. The other luminescent material can be added as a dry material or can also be provided as a dispersion. The luminescent material composition is mixed by stirring, and a liquid containing a mixed dispersion can be obtained. Preferably, the liquid can be removed by evaporation, thereby producing a dry luminescent composition.

[0105] Surprisingly, it has been found that heat-treated luminescent materials in the form of nanoparticles exhibit ideal properties for dispersion into a liquid. Thus, the heat-treated luminescent particles can be dispersed into a dispersion of another luminescent material. Preferably, the dispersion is carried out under vigorous stirring and / or sonication.

[0106] In view of the above, preferably, stages (I) and (II) are achieved before mixing the first luminescent material and the second luminescent material in stage (c).

[0107] In (c), mixing preferably results in a mixture comprising a first luminescent material and a second luminescent material. Preferably, the first luminescent material and the second luminescent material are arranged relative to each other to allow non-radiative energy transfer from the second luminescent material to the first luminescent material. Generally, this involves close proximity between the first and second luminescent materials, such as a distance of about 0.5 nm to about 10 nm. Those skilled in the art are well aware of how to achieve non-radiative energy transfer. For example, this will be described in WO2018 / 167266, the content of which is incorporated herein by reference.

[0108] Luminescent materials, compositions, light-emitting devices, and lighting systems.

[0109] The invention also relates to a luminescent composition obtainable by the method of the invention.

[0110] The invention also relates to a luminescent material obtainable by the method of the invention.

[0111] The luminescent composition and / or luminescent material obtained by the method of the invention can be used in a light-emitting device. Preferably, the light-emitting device further comprises an excitation source for the luminescent material, such as an excitation source for the second luminescent material.

[0112] A light-emitting device comprising the luminescent composition and / or luminescent material of the invention can be used in a lighting system.

[0113] In a preferred embodiment, the lighting system is selected from: lamps or luminaires, office lighting systems, home application systems, store lighting systems, home lighting systems, accent lighting systems, spotlight lighting systems, theater lighting systems, fiber optic application systems, projection systems, self-luminous display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and decorative lighting systems, portable systems, automotive applications, micro-LED-based systems, and greenhouse lighting systems.

[0114] The invention will now be further illustrated with reference to the following examples, however, the invention is not limited thereto.

[0115] Examples

[0116] YAG:Ce 3+ Synthesis of nanoparticles

[0117] The examples described below relate to the synthesis of YAG:Ce nanoparticles by the glycothermal method (J. Mater. Chem. C, 2017, 5, 12561). 3+ TEM analysis shows that the average particle size of the obtained nanoparticles is 6 nm ( Figure 4 The corresponding histogram is shown).

[0118] Comparative experiment A: Annealing without salt

[0119] Perform the following procedure:

[0120] -YAG:Ce 3+ The nanoparticles were synthesized via a sugar thermal method (J. Mater. Chem. C, 2017, 5, 12561).

[0121] -Dry YAG:Ce 3+ particles.

[0122] -YAG:Ce 3+ The pellets were heated in an oven to 1250°C for 30 seconds.

[0123] TEM analysis showed that undesirable sintering occurred and an average diameter of 890 nm was obtained ( Figure 5 The corresponding histogram is shown)

[0124] Example 1

[0125] The following exemplary procedures were performed:

[0126] -YAG:Ce 3+ The nanoparticles were synthesized via a sugar thermal method (J. Mater. Chem. C, 2017, 5, 12561).

[0127] -Preparation of YAG:Ce 3+ 0.25 wt% dispersion of nanoparticles in ethanol.

[0128] - Add pre-ground K2SO4 at a weight ratio of 1:400 YAG:K2SO4.

[0129] -Use an ultrasonic probe to mix the dispersion while allowing the ethanol to evaporate.

[0130] - The mixture is dried.

[0131] - Heat the mixture in an oven to 1050°C for 5 minutes.

[0132] - Wash the mixture with water to remove K2SO4.

[0133] - TEM analysis showed that sintering was minimized and an average grain size of 12 nm was achieved ( Figure 6 The corresponding histograms are shown).

[0134] Example 2

[0135] The following exemplary procedures were performed:

[0136] -YAG:Ce 3+The nanoparticles were synthesized via the saccharothermal method (J. Mater. Chem. C, 2017, 5, 12561).

[0137] - Prepare an aqueous solution of 0.5 M K2SO4.

[0138] - Mix YAG:Ce 3+ with the K2SO4 solution to obtain a dispersion with a concentration of 0.00004 wt%, resulting in a YAG:salt weight ratio of 1:2200. The mixing was enhanced by sonication in an ultrasonic bath for 30 minutes.

[0139] - Add Igepal CO-520 in a volume ratio of 1:2 Igepal:K2SO4 solution.

[0140] - Add cyclohexane in a volume ratio of 1.5:1 cyclohexane:K2SO4 solution.

[0141] - Place the mixture in an ultrasonic bath for 30 minutes for mixing.

[0142] - Add acetone in a volume ratio of 1:15 acetone:mixture volume.

[0143] - Centrifuge the mixture and dry the sediment.

[0144] - Heat the obtained dry powder in an oven to 1050 °C for 5 minutes.

[0145] - Wash the powder with water to remove K2SO4.

[0146] - TEM analysis showed that sintering was minimized and an average particle size of 22 nm was obtained ( Figure 7 the corresponding histogram is shown).

[0147] Example 3:

[0148] The following exemplary procedure was performed:

[0149] - YAG:Ce 3+ precursor was synthesized via the urea precipitation method (Electronic materials 2018, 53, 15196).

[0150] - Prepare an aqueous solution of 0.5 M K2SO4.

[0151] - Mix YAG:Ce 3+ with the K2SO4 solution to obtain a dispersion with a YAG:K2SO4 weight ratio of 1:15. The mixing was enhanced by sonication in an ultrasonic bath for 30 minutes.

[0152] - Add Igepal CO-520 in a volume ratio of 1:4 Igepal:K2SO4 solution.

[0153] - Add cyclohexane in a volume ratio of 2.5:1 cyclohexane:K2SO4 solution.

[0154] - Place the mixture in an ultrasonic bath for 30 minutes to mix.

[0155] - Add acetone in a volume ratio of 1:8 acetone:reaction mixture.

[0156] - Centrifuge the mixture, wash with acetone, and dry the sediment.

[0157] - Heat the obtained dry powder in an oven to 1020 °C for 2 hours.

[0158] - Wash the powder to remove K2SO4.

[0159] - Measure the luminescence of the YAG:Ce 3+ precursor before salt treatment and the YAG:Ce 3+ nanoparticles after heating and removing K2SO4.

[0160] The emission spectra are as Figure 3 shown. Figure 3 shown. Compared with the untreated samples, mixing in a weight ratio of 1:15 YAG:salt, followed by temperature treatment, can significantly increase the luminescence intensity. TEM analysis shows that sintering is minimized. Therefore, the presence of salt can increase the peak intensity without causing particle sintering.

[0161] Example 4

[0162] Perform the following exemplary procedure with YAG:K2SO4 at a weight ratio of 1:1.6:

[0163] - YAG:Ce 3+ nanoparticles are synthesized via the solvothermal method (J.Mater.Chem.C, 2017, 5, 12561).

[0164] - Prepare a 0.5 M aqueous solution of K2SO4.

[0165] - Mix 270 mg of YAG nanoparticles with 5 mL of K2SO4 solution to obtain a weight ratio of 1:1.6. Enhance the mixing by sonication in an ultrasonic bath for 30 minutes.

[0166] - Add Igepal CO-520 in a volume ratio of 2.5:1 Igepal:K2SO4 solution.

[0167] - Add cyclohexane in a volume ratio of 25:1 cyclohexane:K2SO4 solution.

[0168] - Mix the mixture in an ultrasonic bath for 20 minutes.

[0169] - Add acetone in a volume ratio of 1:6 acetone:mixture.

[0170] - Centrifuge the mixture and dry the sediment.

[0171] - Heat the obtained dry powder in an oven to 1200 °C for 2 minutes.

[0172] - Wash the powder with water to remove K2SO4.

[0173] - Analysis by TEM shows that sintering is minimized and an average diameter of 36 nm is obtained ( Figure 8 the corresponding histogram is shown).

[0174] Example 5

[0175] Perform the following exemplary procedure using a YAG:K2SO4 weight ratio of 1:11.8.

[0176] - YAG:Ce 3+ nanoparticles were synthesized via the solvothermal method (J. Mater. Chem. C, 2017, 5, 12561).

[0177] - Prepare an aqueous solution of 0.5 M K2SO4.

[0178] - Mix 74 mg of YAG nanoparticles with 10 mL of K2SO4 solution to obtain a weight ratio of 1:11.8. Mixing was enhanced by sonication in an ultrasonic bath for 30 minutes.

[0179] - Add Igepal CO-520 in a volume ratio of 1:2 Igepal:K2SO4 solution.

[0180] - Add cyclohexane in a volume ratio of 1.5:1 cyclohexane:K2SO4 solution.

[0181] - Mix the mixture in an ultrasonic bath for 20 minutes.

[0182] - Add acetone in a volume ratio of 1:6 acetone:mixture.

[0183] - Centrifuge the mixture and dry the sediment.

[0184] - Heat the obtained dry powder in an oven to 1200 °C for 2 minutes.

[0185] - Wash the powder with water to remove K2SO4.

[0186] Analysis by TEM showed that sintering was minimized and an average diameter of 25 nm was obtained( Figure 9 and the corresponding histogram is shown). The average diameter in this example (applying a YAG:K2SO4 weight ratio of 1:11.8) was found to be lower than the average diameter obtained in Example 4 (applying a YAG:K2SO4 weight ratio of 1:1.6), indicating further reduction in sintering.

[0187] Example 6

[0188] The following exemplary procedure was performed, which included annealing YAG:Ce 3+ nanoparticles in the presence of salt and then mixing the annealed particles with YVPO4:Eu 3+ nanoparticles:

[0189] - YAG:Ce 3+ nanoparticles were synthesized via the solvothermal method (J. Mater. Chem. C, 2017, 5, 12561).

[0190] - A 0.5 M aqueous solution of K2SO4 was prepared.

[0191] - 389 mg of YAG nanoparticles were mixed with 10 mL of the K2SO4 solution to obtain a weight ratio of 1:11.2. The mixing was enhanced by sonication in an ultrasonic bath for 30 minutes.

[0192] - Igepal CO-520 was added at a volume ratio of 1:2Igepal:K2SO4 solution.

[0193] - Cyclohexane was added at a volume ratio of 1.5:1 cyclohexane:K2SO4 solution.

[0194] - The mixture was placed in an ultrasonic bath for 30 minutes for mixing.

[0195] - Acetone was added at a volume ratio of 1:6 acetone:mixture.

[0196] - The mixture was centrifuged and the sediment was dried.

[0197] - Under a N2 atmosphere, the obtained dry powder was heated in an oven to 1000 °C at a rate of 5 °C / min for 4 hours.

[0198] - The powder was washed with water to remove K2SO4.

[0199] - The resulting YAG nanoparticles were mixed with YVPO4:Eu 3+ nanoparticles (CAN GmbH, Series X) with a weight ratio of 1:1 (about 100 mg of each material).

[0200] - Add approximately 15 mL of deionized water to this nanoparticle mixture. Enhance the mixing by sonication in an ultrasonic bath for 1.5 hours.

[0201] - Prepare an alkaline piranha solution: Heat the concentrated NH4OH solution (30% aqueous solution) to 60 °C, add H2O2 (30% aqueous solution) at a ratio of approximately 3:1, and reheat the mixture to 60 °C.

[0202] - Add approximately 15 mL of the alkaline piranha solution to the nanopowder dispersion / solution, heat to 60 - 80 °C and stir for 90 minutes. Then cool the mixture to room temperature and centrifuge.

[0203] - Wash the nanoparticles 5 times with acidic ethanol (pH 4, prepared by adding 0.1 M HCl to ethanol).

[0204] - After the final washing step, dry the mixture and mill it in a mortar.

[0205] - Analysis by HAADF-STEM and EDS elemental mapping showed that nanoscale mixing was achieved.

Claims

1. A method for preparing a luminescent composition, the method comprising: (a) providing a first luminescent material or a precursor thereof, the first luminescent material being capable of emitting light in a first wavelength range; (b) providing a second luminescent material or a precursor thereof, the second luminescent material being capable of absorbing light in a second wavelength range and having an emission spectrum that at least partially overlaps with one or more excitation bands of the first luminescent material; and (c) mixing the first luminescent material or its precursor and the second luminescent material or its precursor, wherein the method further comprises: (I) preparing a mixture comprising (i) the first luminescent material or its precursor and / or the second luminescent material or its precursor and (ii) a salt, wherein the ratio of the salt to the luminescent material in the mixture is greater than 2:1 w / w; and (II) heating the mixture at a temperature of 300 °C or higher; Wherein the first luminescent material or its precursor has a host lattice, and the host lattice is selected from: oxides, fluorides, nitrides, borates, garnets, molybdates, phosphates, vanadates, chlorides, sulfides, selenides, silicates, aluminates, fluorides, chlorooxides, oxynitrides, thioxides, selenoxides, fluorochlorides, fluorosilicates, and fluorobromides, or combinations thereof, and the host lattice is doped with one or more ions selected from Eu 3+ , Ce 3+ , Tb 3+ and Mn 4+ ; Wherein the second luminescent material or its precursor has a host lattice, and the host lattice is selected from: garnet, fluoride, silicate, phosphate, and nitride, or a combination thereof, and the host lattice is doped with one or more ions selected from Eu 2+ , Pb 2+ , Bi 3+ and Ce 3+ ; wherein the salt contains Se 2- , S 2- , Cl - , F - , Br - , I - , SO4 2- , PO4 3- or NO 3- or a combination thereof as an anion, and H + , Li + , Na + , K + , Be 2+ , Ca 2+ , Al 3+ , Ba 2+ , Mg 2+ , or Sr 2+ or a combination thereof as a cation.

2. The method according to claim 1, wherein the method comprises heating the second luminescent material or its precursor at a temperature of at least 300 °C in the presence of a salt.

3. The method according to claim 1, wherein the heating is carried out before the mixing in (c).

4. The method according to claim 1, wherein the first luminescent material or its precursor and / or the second luminescent material or its precursor are in the form of nanoparticles.

5. The method according to claim 4, wherein the first luminescent material or its precursor and the second luminescent material or its precursor are in the form of nanoparticles.

6. The method according to claim 4, wherein the D of the nanoparticles 50 value is ≥ 1 nm and ≤ 100 nm.

7. The method according to claim 1, wherein the first luminescent material or its precursor is doped with one or more ions selected from Eu 3+ , Tb 3+ and Mn 4+ .

8. The method according to claim 1, wherein the first luminescent material is a red luminescent material.

9. The method according to claim 1, wherein the second luminescent material is excitable in a wavelength range of 380 to 580 nm.

10. The method according to claim 9, wherein the second luminescent material is excitable in a high UV-A, violet, blue or green wavelength range.

11. The method according to claim 10, wherein the second luminescent material is excitable in a blue wavelength range.

12. The method according to claim 1, wherein the second luminescent material or its precursor is doped with Ce 3+ .

13. The method according to claim 1, wherein the host lattice of the second luminescent material or its precursor is Y3Al5O 12 or Lu3Al5O 12 or a combination thereof.

14. The method according to claim 13, wherein the second luminescent material or its precursor is doped with Ce 3+ .

15. The method according to claim 1, wherein the mixture comprising (i) the first luminescent material or its precursor and / or the second luminescent material or its precursor and (ii) the salt is obtained or obtainable by a method comprising the following steps (A) Dry mixing (i) the first luminescent material or its precursor and / or the second luminescent material or its precursor and (ii) the salt; or (B) mixing (i) the first luminescent material or its precursor and / or the second luminescent material or its precursor and (ii) the salt into a liquid to obtain a dispersion; or (C) preparing an emulsion comprising a dispersed phase and a continuous phase, the dispersed phase comprising (i) the first luminescent material or its precursor and / or the second luminescent material or its precursor and (ii) the salt.

16. The method according to claim 15, wherein in step (B), the liquid is separated from the dispersion.

17. The method according to claim 15, wherein in step (C), the emulsion is demulsified and the liquid is separated from the demulsified emulsion.

18. The method according to claim 1, wherein the ratio of the salt to the luminescent material in the mixture is greater than 5:1 w / w.

19. The method according to claim 18, wherein the ratio of the salt to the luminescent material in the mixture is greater than 10:1 w / w.

20. A method for treating or obtaining a luminescent material, the method comprising: (I) preparing a mixture comprising (i) a luminescent material and / or its precursor and (ii) a salt, and (II) heating the mixture at a temperature of 300 °C or higher, wherein the ratio of the salt to the luminescent material and / or its precursor in the mixture is greater than 2:1 w / w; wherein the luminescent material comprises a first luminescent material and / or a second luminescent material; and Wherein the first luminescent material and / or its precursor has a host lattice, and the host lattice is selected from: oxides, fluorides, nitrides, borates, garnets, molybdates, phosphates, vanadates, chlorides, sulfides, selenides, silicates, aluminates, fluorides, chlorides, oxynitrides, sulfur oxides, selenium oxides, fluorochlorides, fluorosilicates, and fluorobromides, or combinations thereof, and the host lattice is doped with one or more ions selected from Eu 3+ 、Ce 3+ 、Tb 3+ and Mn 4+ ; wherein the second luminescent material and / or its precursor has a host lattice, and the host lattice is selected from: garnet, fluoride, silicate, phosphate, and nitride, or a combination thereof, and the host lattice is doped with one or more ions selected from Eu 2+ , Pb 2+ , Bi 3+ and Ce 3+ ; wherein the salt contains Se 2- , S 2- , Cl - , F - , Br - , I - , SO4 2- , PO4 3- or NO 3- or a combination thereof as an anion, and H + , Li + , Na + , K + , Be 2+ , Ca 2+ , Al 3+ , Ba 2+ , Mg 2+ , or Sr 2+ or a combination thereof as a cation.

21. The method according to claim 20, wherein the ratio of the salt to the luminescent material and / or its precursor in the mixture is greater than 5:1 w / w.

22. The method according to claim 21, wherein the ratio of the salt to the luminescent material and / or its precursor in the mixture is greater than 10:1 w / w.

23. The method according to claim 1 or 20, wherein the salt is K2SO4.

24. The method according to claim 23, wherein the host lattice of the second luminescent material is Y3Al5O 12 or Lu3Al5O 12 , or a combination thereof.

25. The method according to claim 20, wherein the preparation of the mixture comprises dry mixing (i) the luminescent material or its precursor and (ii) the salt.

26. The method according to claim 25, wherein the dry mixing comprises milling or grinding a mixture comprising (i) the luminescent material or its precursor and (ii) the salt.

27. The method according to claim 20, wherein the preparation of the mixture comprises mixing (i) the luminescent material or its precursor and (ii) the salt into a liquid to obtain a dispersion.

28. The method according to claim 27, wherein the preparation of the mixture further comprises separating the liquid from the dispersion.

29. The method according to claim 28, wherein the liquid is separated from the dispersion by evaporating the liquid.

30. The method according to claim 27, wherein the salt is added to the liquid before, after or simultaneously with the dispersion of the luminescent material in the liquid.

31. The method according to claim 27, wherein the liquid is water or an alcohol.

32. The method according to claim 31, wherein the alcohol is a C1-C4 alkanol.

33. The method according to claim 32, wherein the alcohol is methanol, ethanol or propanol.

34. The method according to claim 27, wherein the mixture is ultrasonically treated.

35. The method according to claim 20, wherein the preparation of the mixture comprises preparing an emulsion comprising a dispersed phase and a continuous phase, the dispersed phase comprising (i) the luminescent material or its precursor and (ii) the salt.

36. The method according to claim 35, wherein the emulsion droplets are separated from the emulsion by sedimentation.

37. The method according to claim 35, wherein the dispersed phase is an aqueous phase and the continuous phase is a non-polar phase or an oil phase.

38. The method according to claim 35, wherein the method comprises preparing the emulsion by ultrasound.

39. The method according to claim 1 or 20, wherein the method further comprises comminuting the salt.

40. The method according to claim 39, wherein the salt is comminuted by grinding or milling.

41. The method according to claim 1 or 20, wherein the mixture comprising (i) the luminescent material or its precursor and (ii) the salt is subjected to sonication, grinding and / or milling.

42. The method according to claim 1 or 20, wherein the luminescent material comprises an organic ligand, and wherein the ligand is selected to enhance mixing with the salt.

43. The method according to claim 1 or 20, wherein the heating comprises heating the mixture at a temperature of 900 °C to 1500 °C.

44. The method according to claim 43, wherein the heating comprises heating for 1 minute to 20 hours.

45. The method according to claim 1 or 20, wherein the method comprises, after the heating, removing the salt from the mixture by contacting the mixture with a solvent.

46. The method according to claim 45, wherein the solvent is water.

47. The method according to claim 42, wherein the organic ligand is removed from the luminescent material.

48. The method according to claim 1 or 20, wherein the first luminescent material or its precursor and / or the second luminescent material or its precursor is crystalline before the heating.

49. The method according to claim 1 or 20, wherein the luminescent material or precursor is amorphous before the heating and / or may not contain all the elements of the final product material.

50. A luminescent composition obtainable by the method according to any one of claims 1 - 19.

51. A luminescent material obtainable by the method according to any one of claims 20 - 49.

52. A light-emitting device comprising the luminescent composition according to claim 50 and / or the luminescent material according to claim 51.

53. The light-emitting device according to claim 52, wherein the light-emitting device further comprises an excitation source for the luminescent material.

54. The light-emitting device according to claim 53, wherein the luminescent material is a second luminescent material.

55. An illumination system comprising the light-emitting device according to claim 52.

56. The illumination system according to claim 55, wherein the illumination system is selected from: illuminators, office lighting systems, home application systems, store lighting systems, residential lighting systems, accent lighting systems, spotlight lighting systems, theater lighting systems, fiber optic application systems, projection systems, self-luminous display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and decorative lighting systems, portable systems, automotive applications, micro-LED-based systems, and greenhouse lighting systems.

57. The illumination system according to claim 56, wherein the illuminator is a lamp.

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