Double-perovskite tungstate red fluorescent powder as well as preparation method and application thereof

Abstract

The invention discloses double-perovskite tungstate red fluorescent powder as well as a preparation method and application thereof, and relates to the field of red fluorescent powder. The chemical formula of the red fluorescent powder is NaGd (MagZnz) 1-2xZrxWO6: Eu < 3 + >, and x is more than 0 and less than 0.5. According to the invention, NaGd (MgZn) WO6 is taken as a matrix material, Zr < 4 + > is introduced for doping, and the NaGd (MgZnz) 1-2x ZrxWO6: Eu < 3 + > double perovskite red fluorescent material with excellent thermal stability is obtained.

Description

Technical Field

[0001] The invention relates to the field of red phosphor materials for WLED, and in particular to a double perovskite tungstate red phosphor and a preparation method and application thereof. Background Art

[0002] Human lighting sources have evolved from the earliest incandescent lamps to fluorescent lamps, high-pressure gas discharge lamps and LEDs, and are gradually developing into high-quality lighting sources. WLED is known as the "green light source" of the 21st century. It has the advantages of high energy conversion efficiency, long service life, high safety and low energy consumption. It has received widespread attention from researchers in recent years.

[0003] The combination of blue light chips and yellow phosphors is currently the mainstream implementation method of commercial WLEDs. However, due to the lack of red light-emitting components, the resulting device has a low color rendering index and a high correlated color temperature. Therefore, another WLED packaging method has emerged, which is to use a combination of near-ultraviolet chips and red, green and blue primary color phosphors. The introduction of the red component has significantly improved the optoelectronic performance of the device.

[0004] Red phosphor plays a key role in WLED devices. However, the luminous intensity of commercial red phosphor materials is prone to thermal quenching when the device operating temperature rises, resulting in a significant deterioration in luminous efficiency. It cannot meet the needs of high-power devices. Therefore, it is crucial to develop efficient red phosphors with excellent thermal stability. Summary of the invention

[0005] The purpose of the present invention is to provide a double perovskite tungstate red phosphor and its preparation method and application, using NaGd (MgZn) WO6 as the matrix material, introducing Zr 4+ Doping to obtain NaGd(Mg y Zn z ) 1- 2x Zr x WO6:Eu 3+ Double perovskite red fluorescent material.

[0006] Specifically, the chemical formula of the double perovskite tungstate red phosphor of the present invention is NaGd(Mg y Zn z ) 1-2x Zr x WO6:Eu 3+ , where 0<x<0.5.

[0007] Zr doping 4+ After that, the traps on the phosphor surface can be more numerous and deeper, thereby capturing more photons. 4+The red phosphor induced by the cation vacancies has high light absorption utilization rate in the near-ultraviolet region - blue light region (365-500nm), high color purity, excellent optical properties, and good thermal stability. The red phosphor of the present invention can be used as a WLED encapsulated with a red component and is suitable for working in a high temperature environment.

[0008] Among them, y:z=9:1, preferably, y=0.9, z=0.1, that is, Mg 2+ and Zn 4+ These two ions with the same charge are co-doped, Mg 2+ and Zn 2+ The molar ratio of Zr is 9:1. 4+ To increase the depth and density of electron traps, as well as the probability of electron capture during energy transfer, thereby improving thermal stability.

[0009] Furthermore, 0<x≤0.12. Preferably, x=0.03 ​​or x=0.07.

[0010] On the other hand, a method for preparing a double perovskite tungstate red phosphor comprises the following steps:

[0011] Place NaNO3, Gd(NO3)3, Mg(NO3)2, Eu(NO3), C6H4O4Zn, and ZrO(NO3)2 in a beaker, and add deionized water to obtain solution A;

[0012] Dissolve citric acid monohydrate in deionized water to obtain solution B;

[0013] Dissolve ammonium metatungstate in distilled water to obtain solution C;

[0014] After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol;

[0015] The pH of the sol was adjusted to weak alkalinity with aqueous ammonia and stirred in a water bath to form a wet gel;

[0016] After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed;

[0017] After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained;

[0018] The fluffy precursor was ground and kept in a muffle furnace at 1100° C. for 6 hours to obtain a red phosphor.

[0019] Furthermore, the present invention also proposes a second invention purpose, which is an application of the above red phosphor in a high-power device, wherein the high-power device includes a WLED device.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] The present invention discloses a double perovskite tungstate red phosphor and its preparation method and application. The present invention uses NaGd(MgZn)WO6 as a matrix material and introduces Zr 4+ Doping to obtain NaGd(Mg y Zn z ) 1-2x Zr x WO6:Eu 3 + Double perovskite red fluorescent material. Doped with Zr 4+ The traps on the surface of the phosphor are more numerous and deeper, thereby capturing more photons. When the temperature is higher, the phosphor of the present invention releases more captured photons, thereby compensating for the missing part of the luminescence performance. Therefore, the thermal stability of the phosphor of the present invention is significantly improved, and it is suitable for working in a high temperature environment, effectively avoiding the problem of thermal quenching when the operating temperature of the device rises.

[0022] Under the excitation of ultraviolet light at 393nm, the color purity is as high as 94% when x=0.03. The phosphor of the present invention is packaged in WLED devices, and the color rendering index is higher than 85, which is better than similar commercial devices. The chromaticity coordinates are close to standard white light (0.333, 0.333), and bright warm white light is emitted. Therefore, the phosphor of the present invention can be used as an excellent red component in high-power devices such as WLED. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0024] Figure 1 1 is the X-ray diffraction pattern of the red phosphor of Examples 1-3 and Comparative Example 1.

[0025] Figure 2 The scanning electron microscope images of the red phosphors of Examples 1-3 and Comparative Example 1 are shown; Figure 2 (a) is a scanning electron microscope image of the red phosphor of Comparative Example 1; Figure 2 (b) is a scanning electron microscope image of the red phosphor of Example 1; Figure 2 (c) is a scanning electron microscope image of the red phosphor of Example 2; Figure 2 (d) is a scanning electron microscope image of the red phosphor of Example 3;

[0026] Figure 3 It is the excitation spectra of the red phosphors of Examples 1-3 and Comparative Example 1 at an emission wavelength of 615 nm.

[0027] Figure 4 The emission spectra and chromaticity coordinates of the red phosphors of Examples 1-3 and Comparative Example 1 are shown in FIG. Figure 4 (a) is the emission spectrum with an excitation wavelength of 393 nm; Figure 4 (b) is the emission spectrum with an excitation wavelength of 464 nm; Figure 4 (c) is the chromaticity coordinate diagram with an excitation wavelength of 393 nm; Figure 4 (d) is the chromaticity coordinate diagram with an excitation wavelength of 464 nm;

[0028] Figure 5 (a) is the temperature-dependent emission spectrum of the phosphor of Example 1 under 393 nm excitation; Figure 5 (b) is the temperature-dependent emission spectrum of the phosphor of Example 2 under 393 nm excitation; Figure 5 (c) is the variable temperature emission spectrum of the phosphor of Example 3 under 393 nm excitation; Figure 5 (d) is a graph of normalized relative luminous intensity of the phosphors of Examples 1-3 and Comparative Example 1;

[0029] Figure 6 (a) is the variable temperature emission spectrum of the phosphor of Example 1 under 464nm excitation; Figure 6 (b) is the temperature-dependent emission spectrum of the phosphor of Example 2 under 464 nm excitation; Figure 6 (c) is the temperature-dependent emission spectrum of the phosphor of Example 3 under 464 nm excitation; Figure 6 (d) is a graph of normalized relative luminous intensity of the phosphors of Examples 1-3 and Comparative Example 1;

[0030] Figure 7 The electroluminescence spectra of the red phosphors of Example 1 and Example 2 are shown in FIG.

[0031] Figure 8 It is a configuration coordinate diagram of the phosphor of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings, but the present invention is not limited to the scope of the embodiments. The experimental methods in the following embodiments without specifying specific conditions are selected according to conventional methods and conditions, or according to the product instructions.

[0033] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] Example 1

[0035] A double perovskite tungstate red phosphor with the chemical formula of NaGd(Mg 0.9 Zn 0.1 ) 1-2x Zr x WO6:Eu 3+ , where x=0.03.

[0036] A method for preparing a double perovskite tungstate red phosphor comprises the following steps:

[0037] 0.1717 g NaNO3, 0.3502 g Gd(NO3)3, 0.4382 g Mg(NO3)2, 0.5358 g Eu(NO3), 0.0416 g C6H4O4Zn, and 0.0139 g ZrO(NO3)2 were placed in a beaker, and deionized water was added to obtain solution A;

[0038] Dissolve 5.0687 g of citric acid monohydrate in deionized water to obtain solution B;

[0039] Dissolve 0.4952 g of ammonium metatungstate in distilled water to obtain solution C;

[0040] After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol;

[0041] The pH of the sol was adjusted to weak alkalinity with aqueous ammonia and stirred in a water bath to form a wet gel;

[0042] After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed;

[0043] After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained;

[0044] The fluffy precursor was ground and kept in a muffle furnace at 1100° C. for 6 hours to obtain the red phosphor of this embodiment.

[0045] Example 2

[0046] A double perovskite tungstate red phosphor with the chemical formula of NaGd(Mg 0.9 Zn 0.1 )1-2x Zr x WO6:Eu 3+ , where x=0.07.

[0047] A method for preparing a double perovskite tungstate red phosphor comprises the following steps:

[0048] 0.1717 g NaNO3, 0.3502 g Gd(NO3)3, 0.4009 g Mg(NO3)2, 0.5358 g Eu(NO3), 0.0381 g C6H4O4Zn, and 0.0325 g ZrO(NO3)2 were placed in a beaker, and deionized water was added to obtain solution A;

[0049] Dissolve 5.0687 g of citric acid monohydrate in deionized water to obtain solution B;

[0050] Dissolve 0.4952 g of ammonium metatungstate in distilled water to obtain solution C;

[0051] After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol;

[0052] The pH of the sol was adjusted to weak alkalinity with aqueous ammonia and stirred in a water bath to form a wet gel;

[0053] After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed;

[0054] After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained;

[0055] The fluffy precursor was ground and kept in a muffle furnace at 1100° C. for 6 hours to obtain the red phosphor of this embodiment.

[0056] Example 3

[0057] A double perovskite tungstate red phosphor with the chemical formula of NaGd(Mg 0.9 Zn 0.1 ) 1-2x Zr x WO6:Eu 3+ , where x=0.12.

[0058] A method for preparing a double perovskite tungstate red phosphor comprises the following steps:

[0059] 0.1717 g NaNO3, 0.3502 g Gd(NO3)3, 0.3543 g Mg(NO3)2, 0.5358 g Eu(NO3), 0.0337 g C6H4O4Zn, and 0.0558 g ZrO(NO3)2 were placed in a beaker, and deionized water was added to obtain solution A;

[0060] Dissolve 5.0687 g of citric acid monohydrate in deionized water to obtain solution B;

[0061] Dissolve 0.4952 g of ammonium metatungstate in distilled water to obtain solution C;

[0062] After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol;

[0063] The pH of the sol was adjusted to weak alkalinity with aqueous ammonia and stirred in a water bath to form a wet gel;

[0064] After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed;

[0065] After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained;

[0066] The fluffy precursor was ground and kept in a muffle furnace at 1100° C. for 6 hours to obtain the red phosphor of this embodiment.

[0067] Comparative Example 1

[0068] A double perovskite tungstate red phosphor with the chemical formula of NaGd(Mg 0.9 Zn 0.1 ) 1-2x Zr x WO6:Eu 3+ , where x=0.

[0069] A method for preparing a double perovskite tungstate red phosphor comprises the following steps:

[0070] 0.1717 g NaNO3, 0.3502 g Gd(NO3)3, 0.4662 g Mg(NO3)2, 0.5358 g Eu(NO3), and 0.0443 g C6H4O4Zn were placed in a beaker, and deionized water was added to obtain solution A;

[0071] Dissolve 5.0687 g of citric acid monohydrate in deionized water to obtain solution B;

[0072] Dissolve 0.4952 g of ammonium metatungstate in distilled water to obtain solution C;

[0073] After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol;

[0074] The pH of the sol was adjusted to weak alkalinity with aqueous ammonia and stirred in a water bath to form a wet gel;

[0075] After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed;

[0076] After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained;

[0077] The fluffy precursor was ground and kept in a muffle furnace at 1100° C. for 6 hours to obtain the red phosphor of Comparative Example 1.

[0078] Experimental Example 1

[0079] (1) X-ray diffraction analysis was performed on the red phosphors in Examples 1-3 and Comparative Example 1.

[0080] The X-ray diffraction patterns of the red phosphors in Examples 1-3 and Comparative Example 1 are as follows: Figure 1 As shown. Figure 1 In the figure, the horizontal axis is the diffraction angle 2θ, and the vertical axis is the diffraction intensity.

[0081] The red phosphors in Examples 1-3 and Comparative Example 1 all have good crystallinity, and the diffraction peaks are relatively sharp, which are consistent with the standard card (NaLaMgWO6 PDF-370243). Figure 1 It can be seen that the red phosphors of Examples 1-3 and Comparative Example 1 are pure-phase monoclinic structures.

[0082] (2) The red phosphors in Examples 1-3 and Comparative Example 1 were tested using a scanning electron microscope.

[0083] Figure 2 (a) is a scanning electron microscope image of the red phosphor of Comparative Example 1; Figure 2 (b) is a scanning electron microscope image of the red phosphor of Example 1; Figure 2 (c) is a scanning electron microscope image of the red phosphor of Example 2; Figure 2 (d) is a scanning electron microscope image of the red phosphor of Example 3. Figure 2 It can be seen that when the doping concentration is x=0 and x=0.03, the sample is polyhedral, especially when x=0.03, the crystallinity is the best, and the particle size is about 200nm-1μm. When the doping concentration is x=0.07 and x=0.12, the morphology and size of the sample change significantly.

[0084] Therefore, from Figure 2 It can be seen that when x=0.03, the crystallinity is the best and has better thermal stability.

[0085] (3) The red phosphors in Examples 1-3 and Comparative Example 1 were subjected to room temperature fluorescence testing.

[0086] Figure 3 The excitation spectra of the red phosphors of Examples 1-3 and Comparative Example 1 are as follows: Figure 3 The horizontal axis is the excitation wavelength, and the vertical axis is the emission intensity. emis the emission wavelength.

[0087] like Figure 3 As shown, the excitation band in the range of 200-350nm is O 2 -→W 6+ The sharp peak in the wavelength range of 350-500 nm is attributed to Eu 3+ ,Eu 3+ The central luminescent ion, Eu 3+ The ff transitions in the matrix lattice correspond to 7 F0→ 5 D4(363nm), 7 F0→ 5 L7(383nm), 7 F0→ 5 L6(393nm), 7 F0→ 5 D3 (418nm) and 7 F0→ 5 D2 (464nm) transition, where 7 F0→ 5 The L6 (393 nm) transition is the strongest absorption peak, which matches well with the output wavelength of the near-ultraviolet light-emitting diode chip, indicating that the phosphors of Examples 1-3 and Comparative Example 1 can be used for WLEDs packaged with near-ultraviolet chips.

[0088] Figure 4 (a) is the emission spectrum with an excitation wavelength of 393 nm. The horizontal axis of the emission spectrum is the wavelength, and the vertical axis is the fluorescence intensity. ex is the excitation wavelength; Figure 4 As shown in (a), under the excitation of 393 nm, the fluorescence intensity of x = 0.03 remains basically unchanged compared with x = 0. 4+ As the doping amount increases, the fluorescence intensity gradually decreases.

[0089] Figure 4 (c) is a chromaticity coordinate diagram with an excitation wavelength of 393 nm. In the chromaticity coordinate diagram, the horizontal axis x represents the relative value related to red, the vertical axis y represents the relative value related to green, and z represents the relative value related to blue, and z=1-(x+y). Figure 4 It can be found from the chromaticity coordinate diagram (c) that the CIE chromaticity coordinates of the red phosphors in Examples 1-3 and Comparative Example 1 are all located in the red region, and have excellent red emission.

[0090] Figure 4 (b) is the emission spectrum with an excitation wavelength of 464 nm, Figure 4 As shown in (b), under the excitation of 464nm, as Zr 4+As the doping amount increases, the fluorescence intensity gradually decreases.

[0091] Figure 4 (d) is the chromaticity coordinate diagram of the excitation wavelength of 464nm. Figure 4 It can be found from the chromaticity coordinate diagram (d) that the CIE chromaticity coordinates of the red phosphors in Examples 1-3 and Comparative Example 1 are all located in the orange-red region.

[0092] The chromaticity coordinates (CIE), correlated color temperature (CCT) and color purity of the red emission in the red phosphors in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0093] Table 1

[0094]

[0095] It can be seen from Table 1 that under the excitation of ultraviolet light and blue light, the red phosphors of Examples 1-3 and Comparative Example 1 can emit warm white light with a color temperature of 1800-2500K.

[0096] Zr doping 4+ The phosphor has good color purity under ultraviolet light (393nm) and blue light (464nm) excitation, close to the purity required for field emission displays, indicating that the red phosphor of Examples 1-3 and Comparative Example 1 is a warm red light phosphor with potential application value.

[0097] Experimental Example 2

[0098] The fluorescence spectra of the phosphors of Examples 1-3 and Comparative Example 1 at different temperatures were plotted. The fluorescence spectra with an excitation wavelength of 393 nm are shown in FIG. Figure 5 As shown, the fluorescence spectrum with an excitation wavelength of 464 nm is Figure 6 shown.

[0099] in, Figure 5 (a) is the temperature-dependent emission spectrum of the phosphor of Example 1 under 393 nm excitation; Figure 5 (b) is the temperature-dependent emission spectrum of the phosphor of Example 2 under 393 nm excitation; Figure 5 (c) is the variable temperature emission spectrum of the phosphor of Example 3 under 393 nm excitation; Figure 5 (d) is a graph of the normalized relative luminous intensity of the phosphors of Examples 1-3 and Comparative Example 1; under ultraviolet light (393 nm) excitation, Eu 3+ The position of the characteristic peak of Zr did not change significantly at different temperatures. As the temperature increased, the luminescence intensity gradually increased and then decreased. At 125°C, the fluorescence intensities of x = 0.03, 0.07, and 0.12 remained at 100%, 100%, and 91% of those at 25°C, respectively.4+ The phosphor with doping concentration x=0.03 can maintain 94% of the relative luminous intensity in a harsh working environment of up to 150°C, and can maintain 94% of the relative luminous intensity when x=0.07, both of which are better than the luminous performance of x=0.

[0100] Combined with the CIE coordinates (x, y) obtained at different temperatures, when x = 0.03, its CIE coordinate change value Δx = 0.01203 and Δy = 0.01195; when x = 0.07, its CIE coordinate change value Δx = 0.01171 and Δy = 0.01163; when x = 0.12, its CIE coordinate change value Δx = 0.01171 and Δy = 0.01163, the above data can prove that NaGd (Mg 0.9 Zn 0.1 ) 1-2x Zr x WO6:Eu 3+ , (0<x≤0.12) phosphor has excellent thermal stability under near-ultraviolet excitation.

[0101] Figure 6 (a) is the temperature-dependent emission spectrum of the phosphor of Example 1 under 464 nm excitation; Figure 6 (b) is the temperature-dependent emission spectrum of the phosphor of Example 2 under 464 nm excitation; Figure 6 (c) is the variable temperature emission spectrum of the phosphor of Example 3 under 464 nm excitation; Figure 6 (d) is a graph of the normalized relative luminous intensity of the phosphors of Examples 1-3 and Comparative Example 1; under the excitation of blue light (464 nm), Eu 3+ The position of the characteristic peak of Zr did not change significantly at different temperatures. As the temperature increased, the luminescence intensity gradually increased and then decreased. At 125°C, the fluorescence intensities of x = 0.03, 0.07, and 0.12 remained at 103%, 101%, and 95% of those at 25°C, respectively. 4+ The phosphor with doping concentration x=0.03 can maintain 98% of the relative luminous intensity in a harsh working environment of up to 150°C, and can maintain 96% of the relative luminous intensity when x=0.07, both of which are better than the luminous performance of x=0.

[0102] Combined with the CIE coordinates (x, y) obtained at different temperatures, when x = 0.03, the CIE coordinate change values ​​Δx = 0.00917 and Δy = 0.0091; when x = 0.07, the CIE coordinate change values ​​Δx = 0.00934 and Δy = 0.00928; when x = 0.12, the CIE coordinate change values ​​Δx = 0.00939 and Δy = 0.00932. The above data can prove that NaGd (Mg0.9 Zn 0.1 ) 1-2x Zr x WO6:Eu 3+ , (0<x≤0.12) phosphor has excellent thermal stability under blue light excitation and is expected to be used in high-power LED devices.

[0103] Experimental Example 3

[0104] The red phosphors obtained in Example 1 and Example 2 (x = 0.03, 0.07) were packaged into WLED devices, and their photoelectric performance was tested. 2+ ) / Blue phosphor (BaMgAl 10 O 17 :Eu 2+ ) was compounded with near-ultraviolet chips (390-395nm), and the encapsulated WLED devices were evaluated for the suitability of the obtained products in normal lighting tools.

[0105] The luminescence performance of the prepared WLED device was measured using a high-precision rapid spectral analysis integrated testing system.

[0106] Figure 7 The corresponding electroluminescence spectrum under stable current driving is shown. The emission band around 393nm corresponds to the NUV chip. Obviously, there are two broad emissions in the blue and green regions, corresponding to the commercial green powder ((Sr,Ba)2SiO4:Eu 2+ ) and commercial blue powder (BaMgAl 10 O 17 :Eu 2+ ). Meanwhile, the sharp peak in the range of 580-730 nm is attributed to Eu 3+ The corresponding transitions of ions. The several emission peaks in the red region correspond to the Eu 3+ of 5 D0→ 7 F1, 5 D0→ 7 F2, 5 D0→ 7 F3 and 5 D0→ 7 F4 transition. Figure 7 It can be concluded that Example 1 and Example 2 can achieve strong warm white light, and are expected to operate and be generally applicable to WLED devices.

[0107] The correlated color temperature (CCT) values ​​of the devices obtained in Example 1 and Example 2 are both below 5000K (warm white light), the chromaticity coordinates are both located in the white light region, and the color rendering index (Ra) values ​​are both above 85. Therefore, the NaGd (Mg 0.9 Zn 0.1 ) 1- 2x Zr x WO6:Eu 3+ Can be used in high-power devices such as WLED.

[0108] Since room temperature fluorescence is not the only criterion for measuring the quality of phosphors, the inventors further conducted variable temperature fluorescence tests on the phosphors of Examples 1-3 and Comparative Example 1.

[0109] The thermal stability of phosphors is one of the key factors in determining whether they can be commercialized. When WLED is working, its operating temperature can reach about 150°C.

[0110] It can be seen from Experimental Examples 1 and 2 that Examples 1-3 and Comparative Example 1 are all expected to be used in the WLED field. However, based on Comparative Example 1, the present invention doped with Zr 4+ , Zr 4+ Doping into Mg 2+ When the site is doped with Zr, cation vacancies are generated. The doping of ions with different charge amounts will produce defect energy levels. The defect energy levels capture electrons that transition from the excited state to the conduction band and store some energy. After heating, due to thermal disturbance, the electrons captured by the defect energy levels will be released back to the 5d excited state, generating additional red light in the 4f band of the transition, thereby increasing thermal stability. In addition, doping with Zr 4+ The traps on the phosphor surface are more numerous and deeper, thus capturing more photons. When the temperature is higher, more captured photons come out, thus compensating for the missing part of the luminescence performance, resulting in the "reverse thermal quenching" effect. Figure 6 At 125 degrees, the relative intensity even reached 103% and 101%, which was caused by the release of captured photons.

[0111] Figure 8 is a configuration coordinate diagram of the phosphor of the present invention, through Figure 8 The thermal quenching mechanism of the phosphor is further revealed. Under near-ultraviolet or blue light excitation, Eu 3+ The electrons from 7 F0 energy level transition to 5 L6 energy level, returns to lower energy through non-radiative transition 5 D0 energy level, then the electron 5 D0 energy level transitions back to the ground state 7 F2 energy level, finally Eu can be obtained at 615nm 3+Typical red emission. As the temperature increases, 5 The electrons at the D0 energy level gain additional energy and reach 5 D0 energy level and 7 The intersection point B of the F2 energy level returns directly to the ground state 7 At F2 energy level, energy will gradually not be released in the form of light energy, Eu 3+ The luminous intensity will gradually weaken. If the activation energy ΔE is larger, the energy required for the electrons to reach the intersection will be greater, and the thermal stability of the phosphor will be better.

[0112] Therefore, as Zr 4+ The thermal stability of the phosphors of Examples 1-3 is higher than that of the phosphors of Examples 1-3 of Comparative Example 1. The luminous intensity of the red phosphor of the present invention will not be thermally quenched when the operating temperature of the device rises, which can improve the luminous efficiency and effectively meet the needs of high-power devices.

[0113] The above descriptions are only some specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A double perovskite tungstate red phosphor, characterized in that: The chemical formula is NaGd(Mg y Zn z ) 1-2x Zr x WO6:Eu 3 + , where 0<x<0.

5.

2. The double perovskite tungstate red phosphor according to claim 1, characterized in that: 0＜x≤0.12。 3. The double perovskite tungstate red phosphor according to claim 1, characterized in that: x＝0.03。 4. The double perovskite tungstate red phosphor according to claim 1, characterized in that: x＝0.07。 5. The double perovskite tungstate red phosphor according to claim 1, characterized in that: y:z=9:

1.

6. The double perovskite tungstate red phosphor according to claim 5, characterized in that: y=0.9,z=0.

1.

7. A method for preparing a double perovskite tungstate red phosphor, characterized in that: The red phosphor according to any one of claims 1 to 6 comprises the following steps: Place NaNO3, Gd(NO3)3, Mg(NO3)2, Eu(NO3), C6H4O4Zn, and ZrO(NO3)2 in a beaker, and add deionized water to obtain solution A; Dissolve citric acid monohydrate in deionized water to obtain solution B; Dissolve ammonium metatungstate in distilled water to obtain solution C; After solution C is clarified, solution A and solution B are added to solution C and mixed to obtain a sol; The pH of the sol was adjusted to a weak alkaline state, and the sol was stirred in a water bath to form a wet gel; After the wet gel is dried in a constant temperature oven, a transparent dry gel is formed; After the transparent dry gel is heated and kept warm, a fluffy precursor is obtained; The fluffy precursor is ground and then calcined in a muffle furnace to obtain red phosphor.

8. The method for preparing a double perovskite tungstate red phosphor according to claim 5, characterized in that: The red phosphor was obtained by keeping the temperature in a muffle furnace at 1100°C for 6 hours.

9. The method for preparing a double perovskite tungstate red phosphor according to claim 5, characterized in that: The pH of the sol was adjusted to weak alkalinity with aqueous ammonia.

10. Use of the red phosphor according to any one of claims 1 to 9 in high-power devices.

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