(19) TZZ ZZ_T (11) EP 2 940 099 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 04.11.2015 Bulletin 2015/45 C09K 11/61 (2006.01) H01L 33/50 (2010.01) (21) Application number: 15165675.8 (22) Date of filing: 29.04.2015 (84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • Lyons, Robert Joseph GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Niskayuna, NY 12309 (US) PL PT RO RS SE SI SK SM TR • Murphy, James Edward Designated Extension States: Niskayuna, NY 12309-1027 (US) BA ME • Setlur jr., Anant Achyut Designated Validation States: Niskayuna, NY 12309 (US) MA (74) Representative: Cleary, Fidelma et al (30) Priority: 01.05.2014 US 201414267434 GPO Europe GE International Inc. (71) Applicant: General Electric Company The Ark Schenectady, NY 12345 (US) 201 Talgarth Road Hammersmith London W6 8BJ (GB) (54) PROCESS FOR PREPARING RED-EMITTING PHOSPHORS (57) The present invention relates to a process for preparing a Mn 4+ doped phosphor of formula I +4 Ax[MFy]:Mn I + n+ includes combining in an acidic solution, an A cation, an anion of formula MFy, and a Mn source comprising a fluoromanganese compound, precipitating a Mn n+ containing phosphor precursor from the acidic solution, and contacting the Mnn+ containing phosphor precursor with a fluorine-containing oxidizing agent in gaseous form, at an elevated temperature, to form the Mn4+ doped phosphor; wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; x is the absolute value of the charge of the [MFy] ion; y is 5, 6 or 7; and n is 2 or 3. EP 2 940 099 A1 Printed by Jouve, 75001 PARIS (FR) EP 2 940 099 A1 Description [0001] Red-emitting phosphors based on complex fluoride materials activated by Mn4+, such as those described in US 7,358,542, US 7,497,973, and US 7,648,649, can be utilized in combination with yellow/green emitting phosphors 5 such as YAG:Ce or other garnet compositions to achieve warm white light (CCTs<5000 K on the blackbody locus, color rendering index (CRI) >80) from a blue LED, equivalent to that produced by current fluorescent, incandescent and halogen lamps. These materials absorb blue light strongly and efficiently emit between about 610-635 nm with little deep red/NIR emission. Therefore, luminous efficacy is maximized compared to red phosphors that have significant emission in the deeper red where eye sensitivity is poor. Quantum efficiency can exceed 85% under blue (440-460 nm) excitation. 10 [0002] Methods for preparation of the phosphors typically require hydrofluoric acid as a solvent. For example, WO 2007/100824 describes preparation of complex fluoride phosphors using aqueous HF as solvent. The processes utilize significant quantities of this highly toxic material, and alternatives that eliminate HF or at least reduce the amount are economically advantageous. [0003] Briefly, in one aspect, the present invention relates to an HF-free process for preparing a Mn 4+ doped phosphor 15 of formula I +4 Ax[MFy]:Mn I wherein 20 A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; 25 x is the absolute value of the charge of the [MF y] ion; y is 5, 6 or 7; and n is 2 or 3. 30 [0004] The process includes combining in an acidic solution, an A+ cation, an anion of formula MFy, and a Mn n+ source comprising a fluoromanganese compound; precipitating a Mn n+ containing phosphor precursor from the acidic solution; and contacting the Mnn+ containing phosphor precursor with a fluorine-containing oxidizing agent in gaseous form, at an elevated temperature, to form the Mn 4+ doped phosphor. 35 [0005] In particular embodiments, a solution of a Mnn+ source in aqueous fluorosilicic acid is added to a solution of n+ 2+ 3+ KF in water to precipitate the Mn containing phosphor precursor, K2SiF6:Mn or K2SiF6:Mn . [0006] Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 40 FIG. 1 is a schematic cross-sectional view of a lighting apparatus in accordance with one embodiment of the invention; FIG. 2 is a schematic cross-sectional view of a lighting apparatus in accordance with another embodiment of the invention; 45 FIG. 3 is a schematic cross-sectional view of a lighting apparatus in accordance with yet another embodiment of the invention; FIG. 4 is a cutaway side perspective view of a lighting apparatus in accordance with one embodiment of the invention; 50 FIG. 5 is a schematic perspective view of a surface-mounted device (SMD) backlight LED. [0007] In the processes of the present invention, an acidic solution is the medium in which the A+ cation, the anion of formula MFy, and the Mnn+ source are combined to form the Mnn+ containing precursor. Suitable acidic solutions are 55 n+ ones in which both the anion of formula MF y, and the Mn fluoroanion of the precursor are stable. The acid may be of formula Hx[MFy]; examples of suitable acids include H2SiF6, H2GeF6, H2TiF6, and combinations thereof. In particular embodiments, the acid is fluorosilicic acid. [0008] The A+ cations may be supplied as a salt, the corresponding anion for A+ may be fluoride, chloride, acetate, 2 EP 2 940 099 A1 chloride, oxalate, dihydrogen phosphate, or a combination thereof, particularly fluoride. Examples of suitable materials include KF, KHF, LiF, LiHF2, NaF, NaHF2, RbF, RbHF2, CsF, CsHF2, and combinations thereof. In particular embodi- ments, the anion is fluoride. The anion of formula MF y may be obtained from the acid of formula H x[MFy], or a compound n+ such as Cs 2SiF6 or MgSiF 6·6H2O may be used. Fluoromanganese compounds suitable for use as the Mn source yield 5 n+ 2+ the Mn fluoroanion when dissolved in the acidic solution. Examples of suitable Mn sources include K 2MnF4, KMnF3, MnF2, manganese (II) acetate, manganese(II) oxide, manganese(II) carbonate, manganese(II) nitrate, and combinations 3+ thereof. Examples of suitable Mn sources include K2MnF5·H2O, KMnF4, and MnF3, manganese (III) acetate, manga- nese(III) oxide, and combinations thereof. Hydrated forms of the Mn n+ sources may produce low concentrations of HF. 4+ Mn sources, such as MnF4, K2MnF6, and MnO2, may also be used, but may have limited stability or solubility in non- 10 HF-containing solutions, leading to manganese reduction. n+ + [0009] The anion of formula MFy, and Mn source are combined with an A cation and an anion of formula MFy in the acidic solution, and the Mnn+ containing phosphor precursor is precipitated. Fluoride or bifluoride anion, or a com- bination thereof may also be present in the solution; a convenient source of the A+ cation and the fluoride or bifluoride + n+ anion may be the fluoride or bifluoride salt of A , AF or AHF2. In particular embodiments, the Mn source is combined 15 + with the acid, which may also provide the anion of formula MF y, and the A cation is added thereto. In some cases, the A+ cation is dissolved in a basic solution, for example, an aqueous solution of a carbonate or hydroxide of A+. The order of addition is not necessarily the same in all embodiments, and in some cases, the KF solution may be added to the n+ acid solution. Amounts of the raw materials for the MFy, anion, the Mn fluoroanion and AF are determined by the stoichiometry of the reaction to form the precursor. 20 [0010] The precursor may be a Mnn+ containing complex fluoride phosphor of formula III n+ Am [MFz]:Mn III wherein A, M, and n are as defined above, 25 m is the absolute value of the charge of the [MF z] ion; and 30 [0011] One example of a Mnn+ containing phosphor precursor that may be formed as an intermediate in a process 3+ according to the present invention is Mn containing K2SiF6. 4+ n+ [0012] In particular embodiments, the phosphor of formula I is K2SiF6:Mn , and the Mn source is combined with n+ n+ the SiF6 anion and KF to yield the Mn containing K2SiF6. For example, the Mn source may be dissolved in aqueous 35 n+ 2+ fluorosilicic acid and added to a solution of KF in water to precipitate the Mn containing phosphor precursor, K 2SiF6:Mn 3+ or K2SiF6:Mn . [0013] In some embodiments, the Mn 4+ doped phosphor of formula I is sparingly soluble in the aqueous acidic solution and precipitates upon formation. If the phosphor is not sufficiently insoluble in the medium to precipitate, a poor solvent may be added to the solution, causing the phosphor to precipitate. Suitable solvents for use as the poor solvent are 40 those that are not attacked by Mnn+ and include alcohols, ketones, carboxylic acids, and phosphoric acid, particularly acetone. [0014] The Mnn+ containing phosphor precursor may be converted to the Mn4+ doped phosphor by contact with a fluorine-containing oxidizing agent in gaseous form at an elevated temperature. The temperature may range from about 200°C to about 700°C, particularly from about 350°C to about 600°C during contact, and in some embodiments from 45 about 200°C to about 700°C.