Red phosphor, preparation method therefor, and use thereof

Abstract

A red phosphor, a preparation method therefor, and a use thereof, relating to the technical field of light-emitting materials. The chemical component of the red phosphor is A2M(1-x)F6:xMn4+, wherein A is selected from at least one of alkali metal elements, M is selected from at least one of group IVA elements or Ti elements, the value range of x is 0<x≤0.05, the phosphor is granular, and the concentration of tetravalent manganese ions in the radial direction from the center of a granule to the surface of the granule is gradually reduced. The concentration of an activating agent Mn4+ in the radial direction from the center of the red phosphor granule to the surface of the red phosphor granule is set to be in gradient descent distribution, so that corrosion of water vapor to a phosphor body is buffered, and the anti-aging performance of the phosphor body is improved, thereby prolonging the service life.

Description

Red phosphor and its preparation method and application Technical Field

[0001] The present application relates to the technical field of luminescent materials, and in particular to a red phosphor and a preparation method and application thereof. Background Art

[0002] In 1973, Paulusz of OSRAM in Germany first reported K2SiF6:Mn 4+ Fluoride fluorescent materials, after 2006, the research of fluoride fluorescent materials gradually became the focus of industrialization, but K2SiF6:Mn activated by tetravalent manganese 4+ The water resistance of phosphor is poor, that is, the Mn 4+ When exposed to moisture in the air, it will be oxidized into dark manganese oxide, causing its brightness to decrease during service, which in turn leads to a short service cycle.

[0003] The related art discloses that the synthesized K2SiF6:Mn 4+ Fluoride phosphors undergo surface reduction, i.e., construct a non-quadrivalent Mn shell structure, which will undoubtedly destroy the crystal structure of the particle surface, resulting in the destruction of the surface manganese-poor layer crystal field structure, reducing the luminous efficiency. The destruction of the surface lattice of the phosphor particles will also bring potential degradation channels to water vapor erosion. In a relatively harsh aging environment, once water molecules penetrate the Mn-free 4+ The activator-doped shell surface creates a water molecule channel, K2SiF6:Mn 4+ The ability of phosphor to resist degradation will drop sharply. 4+ The shell thickness of the activator-doped shell will affect the K2SiF6:Mn 4+ The absorption of blue light by the phosphor reduces the quantum efficiency.

[0004] Summary of the Invention

[0005] The present application provides a red phosphor and a preparation method and application thereof, wherein the activator Mn is added in the radial direction from the center of the red phosphor particle to the surface thereof. 4+ The concentration of tetravalent manganese ions is distributed in a descending gradient to buffer the erosion of water vapor on the phosphor powder; further, the concentration of tetravalent manganese ions on the surface of the red phosphor particles described in the present application is gradually reduced to zero, so as to synthesize a manganese-free shell layer in situ. On the one hand, the manganese-free shell layer avoids the damage to the crystal surface lattice caused by the reducing agent post-treatment and protects the structure of the crystal itself. On the other hand, it can further enhance the anti-aging ability (or anti-deterioration ability) of the phosphor powder.

[0006] In a first aspect, the present application provides a red phosphor, wherein the red phosphor is selected from any one of the substances represented by formula I; A2M (1-x) F6:xMn 4+ Formula I

[0007] In Formula I, A is selected from at least one of the alkali metal elements, M is selected from at least one of the Group IVA elements or the Ti element, the value range of x is 0<x≤0.05, the red phosphor is granular, and the concentration of tetravalent manganese ions in the radial direction from the center of the red phosphor particle to its surface gradually decreases. In some embodiments, in Formula I, A is selected from at least one of the Na element and the K element and M is selected from at least one of the Si element, the Ge element, and the Ti element. In some embodiments, in Formula I, A is selected from at least one of the Na element and the K element or M is selected from at least one of the Si element, the Ge element, and the Ti element. Preferably, in some embodiments, A is a K element or M is a Si element. More preferably, in some embodiments, A is a K element and M is a Si element. The present application achieves this by increasing the concentration of the activator Mn in the radial direction from the center of the red phosphor particle to the surface thereof. 4+ The concentration of phosphor is distributed in a descending gradient to buffer the erosion of water vapor on the phosphor powder, thereby extending the service life of the phosphor.

[0008] In some embodiments, the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles decreases linearly and uniformly. In this way, the phosphor powder has better anti-aging performance and is more conducive to extending the service life.

[0009] In some embodiments, the concentration of tetravalent manganese ions on the surface of the red phosphor particles is zero. In this case, a manganese-free shell layer is in situ formed on the surface of the red phosphor particles, and the manganese-free shell layer can further improve the anti-aging performance of the phosphor powder.

[0010] As shown in Figure 1, the shape of the red phosphor particles is spherical. The position of the center of the red phosphor particles with a spherical structure can be determined with the assistance of a high-energy ion beam. Specifically, the high-energy ion beam cuts along the height center of the red phosphor particles. The cut fresh surface is shown in Figure 2. Two line segments LL′ and L1L1′ connecting the particle surfaces are taken (the two longest line segments available on the fresh surface). The intersection of LL′ and L1L1′ is marked as O. The area enclosed by O as the center and r as the radius can be regarded as the center A of the red phosphor particles described in this application, wherein 0≤r≤0.1R, R is the radius of the red phosphor particles, and the median particle size of the red phosphor particles is 20μm to 40μm. Preferably, the median particle size of the red phosphor particles is 28-32μm, and more preferably, the median particle size of the red phosphor particles is 30μm. A determined by the above method is the center (or body center) of the red phosphor particle, and B is a point randomly selected on the outer edge of the fresh surface of the red phosphor particle. The specific location is not specifically limited in this application, as long as it is on the outer surface of the red phosphor particle. The direction extending from point A to point B is the radial direction from the center of the red phosphor particle to its surface, that is, the Mn in the extension direction from point A to point B is 4+ The concentration of Mn decreases gradually; preferably, the Mn 4+ The concentration of Mn decreases linearly and uniformly; more preferably, the concentration of Mn at point B 4+ The concentration is zero.

[0011] In some embodiments, the manganese atomic percentage at the center of the red phosphor particles is denoted as x1%, and the manganese atomic percentage at the surface of the red phosphor particles is denoted as x2%, satisfying the following: 0≤x2 / x1<1. By controlling the ratio of the manganese atomic content at the surface of the red phosphor particles to the manganese atomic content at their center within an appropriate range, it is beneficial to buffer the erosion of the phosphor powder by water vapor, thereby extending the anti-aging ability of the phosphor powder. Exemplarily, the ratio x2 / x1 of the manganese atomic percentage at the surface of the red phosphor particles to the manganese atomic percentage at the center of the red phosphor particles is 0, 0.05, 0.1, 0.15, 0.18, 0.19, 0.2, 0.25, 0.3, 0.33, 0.35, 0.5, 0.6, 0.7, 0.8, 0.9, or a range consisting of any two of the above values. Preferably, in some embodiments, the following: 0≤x2 / x1≤0.33 is satisfied. More preferably, in some embodiments, the following is satisfied: 0≤x2 / x1<0.2.

[0012] In some embodiments, the manganese atomic percentage content at the center of the red phosphor particle is x1%, satisfying: 0.1≤x1≤5. The manganese atomic percentage content at the center position A of the red phosphor particle can be up to 5%. If the manganese atomic percentage content at the center position of the phosphor particle is too high (for example, higher than 5%), it is not conducive to improving the luminous intensity and the luminous performance is poor; the manganese atomic percentage content at the center position of the phosphor particle should not be lower than 0.1%. If the manganese atomic percentage content at the center position of the phosphor particle is too low (for example, lower than 0.1%), the activator Mn doped in the powder will be 4+ Too low a content is not conducive to improving luminescence performance. For example, the manganese atomic percentage x1% at the center of the red phosphor particles is 0.1%, 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 3%, 4%, 5%, or a range consisting of any two of the foregoing values. Preferably, in some embodiments, the following is satisfied: 0.5 ≤ x1 ≤ 1.

[0013] In some embodiments, the manganese atomic percentage x2% on the surface of the red phosphor particles satisfies the following: 0 ≤ x2 < 0.1. In this case, the anti-aging performance is improved. For example, the manganese atomic percentage x2% on the surface of the red phosphor particles is 0%, 0.01%, 0.03%, 0.05%, 0.06%, 0.08%, 0.09%, or a range consisting of any two of these values.

[0014] In a second aspect, the present application provides a method for preparing the above-mentioned red phosphor, comprising the following steps:

[0015] (1) Obtaining a mixed solution of source A and aqueous hydrofluoric acid solution, recorded as solution A;

[0016] Wherein, the A source includes at least one of A fluoride, A bifluoride salt, A sulfate, A nitrate, A bisulfate, A carbonate or A bicarbonate;

[0017] The mass percentage of hydrofluoric acid in the hydrofluoric acid aqueous solution is 40%.

[0018] (2) Obtain a mixed solution of Mn source and M source (H2MF6 hydrofluoric acid solution), recorded as BX solution;

[0019] Wherein, the mass percentage of H2MF6 in the H2MF6 hydrofluoric acid solution is 20% to 40%; the BX solution includes BX1 solution, BX2 solution, ..., BX n Solution, satisfying: n ≥ 5, the BX1 solution to the BX n The content of Mn source in the solution gradually decreases; optionally, the BX nThe content of Mn source in the solution is 0;

[0020] That is, the BX n The content of Mn source in the solution may be 0 or not. n When the content of Mn source in the solution is 0, a manganese-free shell layer is in situ synthesized on the surface of the red phosphor particles. The manganese-free shell layer can effectively avoid the Mn on the surface of the phosphor particles. 4+ Exposure to moisture in the air further improves the anti-aging ability of the phosphor powder.

[0021] (3) Add the BX solution from (2) to BX1 solution n The solutions are sequentially injected into the A solution of (1) to react, thereby obtaining the red phosphor.

[0022] It should be noted that there is no particular order in which step (1) and step (2) may be performed. Solution A may be prepared first and then solution BX, or solution BX may be prepared first and then solution A. The selection may be based on actual conditions and is not limited in this application.

[0023] In some embodiments, in step (2), the BX1 solution is added to the BX n The content of the Mn source in the solution decreases linearly and uniformly; optionally, the BX1 solution to the BX n The content of the Mn source in the solution decreases uniformly in an arithmetic progression.

[0024] In some embodiments, in step (3), the injection rate of the BX solution is 10-50 mL / s, and the injection interval is 5-15 min; the reaction conditions are: reaction temperature 40-50° C., and reaction time 2-4 h.

[0025] In some embodiments, in step (1), the mass ratio of the A source to the hydrofluoric acid is 20-25:95-105; in step (2), in the BX1 solution, the molar percentage of the Mn source to the M source is recorded as M1, and in the BX1 solution, the molar ratio of the Mn source to the M source is recorded as M1. n In the solution, the molar percentage of the Mn source to the M source is recorded as M2, and satisfies: 0≤M2 / M1<1.

[0026] In a third aspect, the present application discloses the application of the above-mentioned red phosphor or the red phosphor prepared by the above-mentioned preparation method in the field of liquid crystal backlight or LED lighting.

[0027] In a fourth aspect, the present application discloses a liquid crystal backlight source, which includes an excitation chip and a phosphor coated on the excitation chip, wherein the phosphor is the above-mentioned red phosphor or the red phosphor prepared by the above-mentioned preparation method.

[0028] In a fifth aspect, the present application discloses a lighting device, which includes a light-emitting device, and the light-emitting device includes an excitation chip and a phosphor coated on the excitation chip, and the phosphor is the above-mentioned red phosphor or the red phosphor prepared by the above-mentioned preparation method.

[0029] The beneficial effects of the technical solutions provided by some embodiments of the present application include at least: the present application applies the activator Mn in the radial direction from the center of the red phosphor particle to the surface thereof. 4+ The concentration of the phosphor is set to a descending gradient to buffer the erosion of water vapor on the phosphor powder. Compared with the activator Mn in the prior art, 4+ The phosphor powder with no gradient concentration setting has better anti-aging performance. 4+ A linear and uniform decreasing gradient distribution of the concentration of red phosphor powder is more conducive to improving its anti-aging ability than a nonlinear and uneven decreasing gradient distribution, and the service life of the prepared phosphor is longer. At the same time, the present application further reduces the concentration of tetravalent manganese ions on the surface of the red phosphor particles to zero, thereby in situ synthesizing a manganese-free shell layer on the surface of the phosphor powder. This not only helps protect the crystal lattice structure of the crystal itself, but also further improves the anti-aging ability of the phosphor powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 shows the K2SiF6:Mn prepared in Example 1 of this application. 4+ SEM images of phosphors;

[0032] Figure 2 shows the K2SiF6:Mn prepared in Example 1 4+ Fresh surface image of the phosphor after dual-beam ion milling;

[0033] Figure 3 shows the K2SiF6:Mn prepared in Example 1 4+ Line scan path diagram of the phosphor along the EDX line scan from its center A to the surface B;

[0034] FIG4 is an element content diagram of the EDX line scan of FIG3 ;

[0035] Figure 5 shows the K2SiF6:Mn prepared in Example 1 of this application. 4+Schematic diagram of the points taken during energy spectrum analysis of phosphors;

[0036] FIG6 is a graph showing the Mn values ​​at the points of Examples 1 to 5 obtained by testing the points in FIG5 . 4+ Schematic diagram of the distribution curve of relative content. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0038] The present application is further described below through examples. Other fluorescent materials used in the examples of the present application can be purchased through commercial channels.

[0039] Preparation of KSF phosphor (K2SiF6:Mn 4+ Preparation of

[0040] Example 1

[0041] (1) Preparation of BX solution: Weigh 2.7 g, 2.52 g, 2.34 g, 2.16 g, 1.98 g, 1.80 g, 1.62 g, 1.44 g, 1.26 g, 1.08 g, 0.9 g, 0.72 g, 0.54 g, 0.36 g, 0.18 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of commercially available 30% to 32% HSF (i.e., 30% to 32% aqueous fluorosilicic acid solution) to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0042] (2) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution (i.e., 40% hydrofluoric acid aqueous solution) to obtain Solution A;

[0043] (3) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, stirred for 2 h at 40 °C, and allowed to stand for stratification.

[0044] (4) Post-treatment: The supernatant was discarded, 5% HF aqueous solution (5% hydrofluoric acid aqueous solution) was added, and the mixture was stirred and washed twice, and then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0045] The median particle size of the KSF phosphor prepared in Example 1 is 30 μm.

[0046] Figure 1 is the K2SiF6:Mn prepared in Example 1 of this application 4+ The scanning electron microscope image of the phosphor can be seen from Figure 1 that the K2SiF6:Mn 4+ The shape of the phosphor is spherical; Figure 2 shows the K2SiF6:Mn prepared in Example 1. 4+ The fresh surface of the phosphor after double beam ion milling; Figure 3 is the K2SiF6:Mn prepared in Example 1 4+ FIG4 is a schematic diagram of the element content of the EDX line scan of FIG3 . The vertical axis CPS in FIG4 represents the count and has no special physical meaning. It only represents the intensity of the detected element signal. FIG5 is a schematic diagram of the EDX line scan of the phosphor from its center A to the surface B. 4+ Schematic diagram of the point selection when the phosphor is subjected to energy spectrum analysis; FIG6 is a diagram showing the Mn at the point selection method of Example 1 obtained by testing according to FIG5. 4+ Schematic diagram of the distribution curve of the relative content of K2SiF6: Mn prepared in Example 1. 4+ The concentration of tetravalent manganese ions in the radial direction from the center of the red phosphor particle to the surface thereof decreases linearly and evenly to zero.

[0047] Example 2

[0048] (1) Preparation of BX solution: Weigh 2.7 g, 2.23 g, 1.87 g, 1.57 g, 1.34 g, 1.14 g, 0.95 g, 0.74 g, 0.59 g, 0.46 g, 0.34 g, 0.22 g, 0.15 g, 0.07 g, 0.03 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of commercially available 30% to 32% HSF to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0049] (2) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution to obtain Solution A;

[0050] (3) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 15 mL / s with an interval of 10 min, stirred for 4 h at 50 °C, and allowed to stand for stratification;

[0051] (4) Post-treatment: The supernatant was discarded, 5% HF aqueous solution was added, stirred and washed twice, and then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0052] The median particle size of the KSF phosphor prepared in Example 2 is 30 μm.

[0053] As can be seen from FIG6 , the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles prepared in Example 2 decreases nonlinearly to zero.

[0054] Example 3

[0055] (1) Preparation of BX solution: Weigh 2.7 g, 1.77 g, 1.27 g, 1.00 g, 0.79 g, 0.61 g, 0.48 g, 0.39 g, 0.30 g, 0.23 g, 0.17 g, 0.12 g, 0.08 g, 0.04 g, 0.02 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of commercially available 30% to 32% HSF to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0056] (2) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution to obtain Solution A;

[0057] (3) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 35 mL / s and at intervals of 13 min. The mixture was stirred for 3 h at 45 °C and allowed to stand for stratification.

[0058] (4) Post-treatment: The supernatant was discarded, 5% HF aqueous solution was added, stirred and washed twice, and then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0059] The median particle size of the KSF phosphor prepared in Example 3 is 30 μm.

[0060] As can be seen from FIG6 , the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles prepared in Example 3 decreases nonlinearly and non-uniformly to zero.

[0061] Example 4

[0062] (1) Preparation of BX solution: Weigh 2.7 g, 2.65 g, 2.6 g, 2.52 g, 2.43 g, 2.37 g, 2.24 g, 2.07 g, 1.91 g, 1.76 g, 1.57 g, 1.38 g, 1.16 g, 0.86 g, 0.52 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of commercially available 30% to 32% HSF to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0063] (2) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution to obtain Solution A;

[0064] (3) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 50 mL / s with an interval of 15 min, stirred for 4 h at a temperature of 45 °C, and allowed to stand for stratification;

[0065] (4) Post-treatment: The supernatant was discarded, 5% HF aqueous solution was added, stirred and washed twice, and then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0066] The median particle size of the KSF phosphor prepared in Example 4 is 30 μm.

[0067] As can be seen from FIG6 , the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles prepared in Example 4 decreases nonlinearly to zero.

[0068] Example 5

[0069] (1) Preparation of BX solution: Weigh 2.7 g, 2.69 g, 2.68 g, 2.68 g, 2.66 g, 2.63 g, 2.58 g, 2.51 g, 2.40 g, 2.25 g, 2.05 g, 1.81 g, 1.58 g, 1.32 g, 0.89 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of commercially available 30% to 32% HSF to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0070] (2) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution to obtain Solution A;

[0071] (3) Add the prepared BX solution to BX1 solution 16The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, stirred for 2 h at a temperature of 45 °C, and allowed to stand for stratification;

[0072] (4) Post-treatment: The supernatant was discarded, 5% HF aqueous solution was added, stirred and washed twice, and then washed twice with anhydrous ethanol, and dried under forced air drying conditions at 60°C.

[0073] The median particle size of the KSF phosphor prepared in Example 5 is 30 μm.

[0074] As can be seen from FIG6 , the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles prepared in Example 5 decreases nonlinearly and non-uniformly to zero.

[0075] Table 1

[0076] Preparation of other phosphors

[0077] Example 1

[0078] (1) In an ice-water bath, add 150 g of germanium oxide GeO2 to 850 g of 50% hydrofluoric acid aqueous solution and mechanically stir for 1 h to obtain a 30% by mass fluorogermanic acid H2GeF6 solution.

[0079] (2) Preparation of BX solution: Weigh 2.7 g, 2.52 g, 2.34 g, 2.16 g, 1.98 g, 1.80 g, 1.62 g, 1.44 g, 1.26 g, 1.08 g, 0.9 g, 0.72 g, 0.54 g, 0.36 g, 0.18 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of homemade 30% fluorogermanic acid to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0080] (3) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution (i.e., 40% hydrofluoric acid aqueous solution) to obtain Solution A;

[0081] (4) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, stirred for 2 h at 40 °C, and allowed to stand for stratification.

[0082] (5) Post-treatment: The supernatant was discarded, 5% HF aqueous solution (5% hydrofluoric acid aqueous solution) was added, stirred and washed twice, then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0083] Example 1 Preparation of K2Ge (1-x) F6:xMn 4+ The median particle size of the phosphor was 30 μm.

[0084] Example 2

[0085] (1) In an ice-water bath, 146 g of titanium dioxide TiO2 was added to 854 g of a 50% aqueous hydrofluoric acid solution and mechanically stirred for 1 h to obtain a 30% by mass fluorogermanic acid H2TiF6 solution.

[0086] (2) Preparation of BX solution: Weigh 2.7 g, 2.52 g, 2.34 g, 2.16 g, 1.98 g, 1.80 g, 1.62 g, 1.44 g, 1.26 g, 1.08 g, 0.9 g, 0.72 g, 0.54 g, 0.36 g, 0.18 g, and 0 g of K2MnF6, respectively, and dissolve them in 50 g of homemade 30% fluorotitanic acid to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.7 g of K2MnF6), BX2 solution, ..., BX 16 Solution (without K2MnF6);

[0087] (3) Preparation of Solution A: Weigh 21 g of potassium bifluoride and dissolve it in 250 ml of 40% HF aqueous solution (i.e., 40% hydrofluoric acid aqueous solution) to obtain Solution A;

[0088] (4) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, stirred for 2 h at 40 °C, and allowed to stand for stratification;

[0089] (5) Post-treatment: The supernatant was discarded, 5% HF aqueous solution (5% hydrofluoric acid aqueous solution) was added, stirred and washed twice, then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0090] Example 2 Preparation of K2Ti (1-x) F6:xMn 4+ The median particle size of the phosphor was 30 μm.

[0091] Example 3

[0092] (1) In an ice-water bath, 344 g of germanium oxide GeO2 was added to 656 g of a 50% aqueous hydrofluoric acid solution and mechanically stirred for 1 h to obtain a 30% by mass fluorogermanic acid H2GeF6 solution.

[0093] (2) Preparation of BX solution: Weigh 2.35 g, 2.19 g, 2.04 g, 1.88 g, 1.72 g, 1.57 g, 1.41 g, 1.25 g, 1.10 g, 0.94 g, 0.78 g, 0.63 g, 0.47 g, 0.31 g, 0.16 g, and 0 g of Na2MnF6, respectively, and dissolve them in 50 g of homemade 30% fluorogermanic acid to obtain 16 groups of BX solutions, namely, BX1 solution (containing 2.35 g of Na2MnF6), BX2 solution, ..., BX 16 Solution (without Na2MnF6);

[0094] (3) Preparation of Solution A: Weigh 16.6 g of sodium fluoride and dissolve it in 250 ml of 40% HF aqueous solution (i.e., 40% hydrofluoric acid aqueous solution) to obtain Solution A;

[0095] (4) Add the prepared BX solution to BX1 solution 16 The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, stirred for 2 h at 40 °C, and allowed to stand for stratification.

[0096] (5) Post-treatment: The supernatant was discarded, 5% HF aqueous solution (5% hydrofluoric acid aqueous solution) was added, stirred and washed twice, then washed twice with anhydrous ethanol, and dried at 60°C under forced air drying conditions.

[0097] Example 3 Preparation of Na2Ge (1-x) F6:xMn 4+ The median particle size of the phosphor was 30 μm.

[0098] Energy spectrum analysis test

[0099] The KSF phosphors prepared in Examples 1 to 5 were cut using dual ion beam cutting, and 16 points were evenly spaced from the center A to the surface B on the fresh surface for energy spectrum analysis, as shown in FIG5 . FIG5 is a schematic diagram of the points taken when the KSF phosphor prepared in Example 1 was subjected to energy spectrum analysis. The atomic percentages of Mn at the taken points are shown in Table 2 and FIG6 . The point taking method for the KSF phosphors prepared in Examples 2 to 5 can refer to the point taking method of Example 1 in FIG5 . The atomic percentages of Mn at the taken points are shown in Table 2 and FIG6 , which will not be repeated here.

[0100] Table 2

[0101] Combining Table 2 and FIG6 , it can be seen that the concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particles prepared in Examples 1 to 5 gradually decreases. 4+ The decreasing trend of concentration shows that the Mn 4+ The concentration of Mn decreases linearly and evenly in the radial direction from the center of the particle to its surface, especially in an arithmetic progression. The decreasing trend is a straight line, and the distances between two adjacent points on the straight line are equal. 4+ The concentration of Mn decreases non-uniformly in the radial direction from the center to the surface, and the decreasing trend is a curve-like decrease. In addition, the Mn 4+ The concentrations are all 0.

[0102] Example 6

[0103] Similar to Example 1, except that: in the process of preparing BX solution, only BX1 solution to BX 10 In the solution, that is, the KSF phosphor prepared in Example 6, the ratio x2 / x1 of the atomic percentage content x2 of manganese on its surface to the atomic percentage content x1 of manganese in its center is 0.395.

[0104] Example 7

[0105] Similar to Example 1, except that: in the process of preparing BX solution, only BX1 solution to BX 12 The solution, that is, the KSF phosphor prepared in Example 7 does not contain a manganese-free outer shell layer, and the ratio x2 / x1 of the atomic percentage content x2 of manganese on its surface to the atomic percentage content x1 of manganese in its center is 0.26.

[0106] Example 8

[0107] Similar to Example 1, except that: in the process of preparing BX solution, only BX1 solution to BX 14 The solution, that is, the KSF phosphor prepared in Example 8 does not contain a manganese-free outer shell layer, and the ratio x2 / x1 of the atomic percentage content x2 of manganese on its surface to the atomic percentage content x1 of manganese in its center is 0.14.

[0108] Comparative Example 1

[0109] Similar to Example 1, except that: in the process of preparing BX solution, all K2MnF6 was directly added to 10%-15% HSF, that is, it was not added in a descending gradient. Specifically, 21.6g K2MnF6 was weighed and dissolved in 800g commercially available 10%-15% HSF, and the solution was divided into 16 equal parts, thus obtaining 16 groups BX1 to BX with the same K2MnF6 content. 16 Solution; then the BX1 ~ BX 16 The solutions were sequentially injected into solution A at an injection rate of 10 mL / s at intervals of 6 min, and the rest was the same as in Example 1.

[0110] Table 3 shows the test method and equipment for the 1000-hour aging test in this application, and Table 4 shows the aging test data of the phosphors prepared in Examples 1 to 8, Examples 1 to 2, and Comparative Example 1. (Note: KSF-0 is the sample of Comparative Example 1, KSF-1 is the sample of Example 1, KSF-2 is the sample of Example 2, KSF-3 is the sample of Example 3, KSF-4 is the sample of Example 4, KSF-5 is the sample of Example 5, KSF-6 is the sample of Example 6, KSF-7 is the sample of Example 7, KSF-8 is the sample of Example 8, KSF-9 is the sample of Example 1, KSF-10 is the sample of Example 2, and KSF-11 is the sample of Example 3)

[0111] Table 3

[0112] Table 4

[0113] Combined with the data in Table 4, it can be seen that the gradual decrease in the concentration of tetravalent manganese ions in the phosphor particles along the radial direction is beneficial to the improvement of the anti-aging performance. For Comparative Example 1 in which the tetravalent manganese ion concentration is set without a gradient, the luminous flux value of Comparative Example 1 at 0h is 128.30lm, and the luminous flux of Comparative Example 1 after 1000h of use is only 123.56lm, a decrease of 4.74lm. In addition, the brightness ratio of the phosphor prepared in Comparative Example 1 after 1000h of use is significantly reduced from 100% at the beginning to 96.2%; while in Example 1 in which the tetravalent manganese ion concentration is set with a decreasing gradient along the radial direction as described in the present application, the luminous flux of Example 1 after 1000h of use is only reduced by 1.16lm compared with the luminous flux at 0h, and the brightness ratio of the phosphor prepared in Example 1 after 1000h of use can be as high as 99.1%. It can be seen that the phosphor using the tetravalent manganese ion concentration set with a decreasing gradient has a longer service life. Comparing KSF-2 to KSF-5 with KSF-1, it can be seen that the linear and uniform decrease in the concentration of tetravalent manganese ions along the radial direction from the center to the surface of the phosphor particles is more conducive to improving its anti-aging performance and has a stronger ability to delay water vapor erosion.

[0114] Comparing KSF-9 to KSF-11 with KSF-1, it can be seen that when A is K element and M is Si element, the phosphor has the best performance, and for the selection of A source and M source, potassium bifluoride and fluorosilicic acid are preferred.

[0115] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A red fluorescent powder, It is characterized in that The red phosphor is selected from any one of the substances shown in Formula I; 2 M (1-x) F 6 :xMn 4+ Formula I In Formula I, A is selected from at least one of alkali metal elements; M is selected from at least one of Group IVA elements or Ti elements; The value range of x is 0<x≤0.05; The red phosphor is in granular form; The concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particle gradually decreases.

2. The red phosphor according to claim 1, It is characterized in that In Formula I, A is selected from at least one of Na and K; and / or, M is selected from at least one of Si element, Ge element and Ti element.

3. The red phosphor according to claim 1, It is characterized in that The concentration of tetravalent manganese ions in the radial direction from the center to the surface of the red phosphor particle decreases linearly and uniformly.

4. The red phosphor according to claim 1, It is characterized in that The concentration of tetravalent manganese ions on the surface of the red phosphor particles is zero.

5. The red phosphor according to claim 1, It is characterized in that The manganese atomic percentage content in the center of the red phosphor particle is denoted as x 1 %, and the manganese atomic percentage content on the surface of the red phosphor particles is recorded as x 2 %, satisfying: 0≤x 2 / x 1 <1.

6. The red phosphor according to claim 5, It is characterized in that Satisfies: 0≤x 2 / x 1 ≤0.

33.

7. The red phosphor according to claim 5, It is characterized in that The manganese atomic percentage content x in the center of the red phosphor particle 1 %, satisfying: 0.1≤x 1 ≤5.

8. The red phosphor according to claim 7, It is characterized in that The manganese atomic percentage content x in the center of the red phosphor particle 1 %, satisfying: 0.5≤x 1 ≤1.

9. The red phosphor according to claim 5, It is characterized in that The manganese atomic percentage content x on the surface of the red phosphor particles 2 %, satisfying: 0≤x 2 ≤0.

1.

10. The method for preparing the red phosphor according to any one of claims 1 to 9, It is characterized in that The following steps are involved: (1) obtaining a mixed solution of source A and aqueous hydrofluoric acid solution, denoted as solution A; (2) obtaining a mixed solution of a Mn source and a M source, denoted as a BX solution; The BX solution includes BX 1 Solution, BX 2 Solution, ..., BX n solution, and satisfies: n≥5, the BX 1 Solution to the BX n The content of Mn source in the solution gradually decreases; Optionally, the BX n The content of Mn source in the solution is 0; (3) The BX solution in (2) is adjusted according to BX 1 Solution to BX n The solutions are sequentially injected into the A solution of (1) to react, thereby obtaining the red phosphor.

11. The preparation method according to claim 10, It is characterized in that In step (2), the BX 1 Solution to the BX n The content of Mn source in the solution decreases linearly and uniformly; Optionally, the BX 1 Solution to the BX n The content of the Mn source in the solution decreases uniformly in an arithmetic progression.

12. The preparation method according to claim 10, It is characterized in that In step (3), the injection rate of the BX solution is 10 to 50 mL / s, and the injection interval is 5 to 15 min; The reaction conditions are: reaction temperature 40-50° C., reaction time 2-4 h.

13. The preparation method according to claim 10, It is characterized in that In step (1), the mass ratio of the A source to the hydrofluoric acid is 20-25:95-105; In step (2), in the BX 1 In the solution, the molar percentage of the Mn source to the M source is recorded as M 1 , in the BX n In the solution, the molar percentage of the Mn source to the M source is recorded as M 2 , satisfying: 0≤M 2 / M 1 <1.

14. Use of the red phosphor according to any one of claims 1 to 9 or the red phosphor prepared by the preparation method according to any one of claims 10 to 13 in the field of liquid crystal backlight or LED lighting.

15. A liquid crystal backlight source, It is characterized in that It includes an excitation chip and phosphor coated on the excitation chip; The phosphor is the red phosphor according to any one of claims 1 to 9; or The phosphor is a red phosphor prepared by the preparation method according to any one of claims 10 to 13.

16. A lighting device, It is characterized in that including a light emitting device; The light emitting device comprises an excitation chip and phosphor coated on the excitation chip; The phosphor is the red phosphor according to any one of claims 1 to 9; or The phosphor is a red phosphor prepared by the preparation method according to any one of claims 10 to 13.

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