High-thermal-stability blue-green germanate fluorescent powder, preparation method and application thereof

Abstract

This invention belongs to the field of inorganic luminescent materials technology, and provides a highly thermally stable blue-green germanate phosphor, its preparation method, and its applications. The chemical composition formula of this blue-green germanate phosphor is: Ba 1.98 MgGe2O7:0.01Bi 3+ The preparation method includes: (1) weighing the raw material powder separately; (2) grinding and pouring it into an alumina crucible; (3) sintering the alumina crucible containing the mixture. This phosphor uses the traditional high-temperature solid-state method to synthesize a new bismuth-doped germanate phosphor matrix in an atmospheric pressure air atmosphere. Not only is the synthesis method simple, but the prepared sample has no overlap between the excitation spectrum and the emission spectrum under the premise of wide absorption in the ultraviolet region, which can effectively avoid the phenomenon of spectral reabsorption. It can supplement the missing blue-green light region in white LEDs and match well with existing commercial 365nm near-ultraviolet LED chips. It can solve the problem that most phosphor systems cannot maintain excellent luminescence performance in high-temperature environments above 200℃.

Description

Technical Field

[0001] This invention belongs to the field of inorganic luminescent materials technology, specifically relating to a high thermal stability blue-green germanate phosphor, its preparation method, and its application. Background Technology

[0002] White light-emitting diode (LED) lighting devices have become the core of the next generation of solid-state lighting due to their advantages such as high efficiency, energy saving, environmental friendliness, and miniaturization. Currently, commercial solutions generally use blue LED chips to excite yellow phosphors, that is, coating a blue LED chip (440-470nm) with yellow CeO2. 3+ Yttrium aluminum garnet (YAG:Ce) 3+ The system uses phosphors for production, but the lack of red light component results in a low color rendering index and a high color temperature. Furthermore, the white LED spectrum exhibits a significant "gap" in the blue-green light band. In addition, researchers combined ultraviolet LED chips (350-420nm) with red, green, and blue phosphors to achieve full-spectrum lighting. However, for these traditional white LEDs, the missing portion of their emission spectrum in the blue-green light band significantly reduces the color rendering index (CRI), thus greatly limiting their application in high-quality lighting.

[0003] Therefore, there is an urgent need to develop blue-green light phosphors to fill the blue-green light gap problem in white LEDs.

[0004] Many blue-green phosphor systems have been reported, but most of these systems have poor thermal stability and face severe thermal quenching at 150℃. For LED devices, the process of emitting light generates heat, causing the device temperature to rise continuously; therefore, the thermal stability of the phosphor is crucial.

[0005] Among the many blue-green phosphor systems, rare-earth ion-doped luminescent materials dominate the field of solid-state lighting. With their rich energy level structures and diverse electronic transition mechanisms, they can achieve emission from ultraviolet and visible to infrared, while also possessing high color purity and stable excitation / emission peak characteristics, attracting considerable attention for a long time. However, as a non-renewable strategic resource, they face severe supply pressure and environmental pollution problems, and the raw material cost is relatively high. In terms of optical performance, some narrow-band emitting rare-earth ions, such as Eu... 3+ Yb 3+ Er 3+ These rare earth ions exhibit narrow-band excitation and emission with fixed peak positions, resulting in insufficient absorption of excitation light and leakage, leading to low luminous efficiency. Some broadband-emitting rare earth ions, such as Eu... 2+ Ce 3+Although these rare earth ions exhibit broadband excitation and emission, their excitation and emission spectra overlap to some extent, resulting in spectral reabsorption.

[0006] Transition metal ions (Cr) 3+ Mn 4+ Ni 2+ Doped systems (such as those containing excitation and emission spectra) exhibit strong broadband absorption characteristics in the ultraviolet-visible region, and their near-infrared emission can cover the first biological optical window and even extend to the second biological optical window, showing great potential in fields such as bioimaging and detection. However, these materials pose a risk of biotoxicity, and the overlap between excitation and emission spectra can easily lead to self-absorption effects, limiting their practical performance.

[0007] In this context, bismuth ions (Bi 3+ Doped materials have sparked a research boom due to their unique spectral tunability. 3+ Unique [Xe]4f 14 5d 10 6s 2 Its electronic configuration makes its 6s 2 Lone pairs of electrons are extremely sensitive to changes in the local microenvironment (crystal field / coordination structure / defect states). By controlling parameters such as fabrication process, matrix composition, excitation wavelength, or temperature, emission from the ultraviolet to the near-infrared can be achieved. However, this type of system has a fatal flaw: a significant high-temperature thermal quenching effect, which hinders its application in solid-state lighting.

[0008] In summary, finding a bismuth-doped phosphor system that can solve the above problems and possess both high ultraviolet responsivity and high thermal stability, and that can precisely fill the emission gap in the blue-green light band (480-520nm) of white LEDs to improve the performance limit of high color rendering index lighting devices, has become an urgent problem to be solved. Summary of the Invention

[0009] To address the aforementioned shortcomings of existing technologies, this invention aims to provide a highly thermally stable blue-green germanate phosphor, its preparation method, and its applications. This blue-green germanate phosphor utilizes a traditional high-temperature solid-state method to synthesize a novel bismuth-doped germanate phosphor matrix in an ambient air atmosphere. This method is not only simple to implement, but also produces a sample with broad absorption in the ultraviolet region and no overlap between excitation and emission spectra, effectively avoiding spectral reabsorption. Furthermore, it can fill the missing blue-green light region in white LEDs and exhibits good compatibility with existing commercial 365nm near-ultraviolet LED chips. This solves the problem that most phosphor systems cannot maintain excellent luminescence performance at temperatures above 200°C, providing more options for phosphor applications.

[0010] To achieve the above objectives, the solution adopted by the present invention is:

[0011] A highly thermally stable blue-green germanate phosphor, with the chemical composition formula: Ba 1.98 MgGe2O7:0.01Bi 3+ .

[0012] Furthermore, in a preferred embodiment of the present invention, the emission wavelength of the blue-green germanate phosphor is in the blue-green light band of 480-520nm.

[0013] A method for preparing the above-mentioned high thermal stability blue-green germanate phosphor includes: (1) weighing Ba2CO3, MgO, GeO2 and Bi2O3 raw material powders according to a molar ratio of 1.98:1:2:0.01; (2) placing the weighed raw material powders in an agate mortar for grinding, and after grinding, a mixture is obtained, and the mixture is poured into a clean alumina crucible; (3) transferring the alumina crucible containing the mixture to a high-temperature muffle furnace for sintering to obtain the phosphor.

[0014] Furthermore, in a preferred embodiment of the present invention, the grinding time is 45 minutes.

[0015] Furthermore, in a preferred embodiment of the invention, the sintering conditions include: raising the temperature to 1100°C in an air atmosphere. o C, keep warm for 6 hours, then cool down to 500°C. o C, then allowed to cool naturally to room temperature, removed and ground again to obtain a blue-green germanate phosphor with high thermal stability.

[0016] Furthermore, in a preferred embodiment of the present invention, the heating rate is 5. o C / min, cooling rate is 5 o C / min.

[0017] Application of the above-mentioned high thermal stability blue-green germanate phosphor in the preparation of ultraviolet chip white LEDs and ultraviolet chip full-spectrum LEDs.

[0018] The beneficial effects of the high thermal stability blue-green germanate phosphor, its preparation method, and its application provided by this invention are as follows:

[0019] (1) The blue-green germanate phosphor with high thermal stability provided by the present invention can maintain a thermal stability of greater than 200°C. o It maintains excellent luminescence performance even at high temperature environments, achieving 150-200 o The luminous intensity decay rate is less than 15% in the C operating temperature range, which meets the thermal management requirements of high-power LED chip packaging.

[0020] (2) The high thermal stability blue-green germanate phosphor provided by the present invention constructs a novel germanate matrix crystal structure, which can precisely control the emission wavelength in the 480-520nm blue-green light band, supplement the missing blue-green light band in the white light LED spectrum, and solve the problem of missing blue-green light region;

[0021] (3) The blue-green germanate phosphor with high thermal stability provided by the present invention has almost no overlap between its excitation spectrum and emission spectrum in terms of spectral performance, which can avoid the problem of reabsorption of emitted light when used by itself or other materials at the same time.

[0022] (4) The preparation method of the high thermal stability blue-green germanate phosphor provided by the present invention uses the traditional high temperature solid phase method to prepare the sample in the normal pressure air atmosphere, which avoids the operation of adding atmosphere, reduces cost and simplifies process. The preparation process is simple, the performance is good, and the material can be mass-produced. At the same time, it avoids the use of rare earth elements as the main luminescent ions, which alleviates the pressure of rare earth resources in my country to a certain extent.

[0023] (5) The high thermal stability blue-green germanate phosphor provided by this invention has good compatibility with commercial near-ultraviolet LED chips in commercial applications: the excitation peak of this material is located near 362nm, which is highly consistent with the emission spectrum of mainstream commercial 365nm near-ultraviolet LED chips. It can be used to prepare high-quality white LEDs such as ultraviolet chip white LEDs and ultraviolet chip full-spectrum LEDs. Attached Figure Description

[0024] Figure 1 These are the X-ray diffraction (XRD) spectra of the phosphors provided in Experimental Example 1 and Comparative Examples 1-4 of this invention;

[0025] Figure 2 These are the excitation and emission spectra of the phosphors provided in Example 1 and Comparative Examples 1-3 of the present invention;

[0026] Figure 3 This is a graph showing the trend of luminescence intensity of the phosphors provided in Embodiment 1 and Comparative Examples 1-3 of the present invention as a function of temperature;

[0027] Figure 4 These are photographs of the phosphor provided in Embodiment 1 of the present invention under ultraviolet light irradiation at different temperatures. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0030] Example 1

[0031] This embodiment provides a highly thermally stable blue-green germanate phosphor, the preparation method of which includes:

[0032] (1) Using the preparation of 0.0015 mol sample as the standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element of the target product, and then the materials were accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying or synthesis. Ba2CO3, MgO, GeO2 and Bi2O3 were weighed according to the chemical composition Ba-Mg-Ge-O-Bi, with a molar ratio of 1.98:1:2:0.01. That is, 1.1726 g of Ba2CO3, 0.1209 g of MgO, 0.6278 g of GeO2 and 0.0070 g of Bi2O3 were weighed. In order to reduce the experimental error, the error between the weighing result and the calculation result was controlled within ±0.3 mg.

[0033] (2) Place the weighed raw material powder in an agate mortar and grind it for 45 minutes.

[0034] (3) Transfer the alumina crucible containing the mixture to a high-temperature muffle furnace for sintering: raise the temperature to 1100℃ in an air atmosphere at a heating rate of 5℃ / min, hold for 6h, lower the temperature to 500℃ at a cooling rate of 5℃ / min, and then let it cool naturally to room temperature. Take it out and grind it again until there is no obvious particle feel, and obtain the fluorescent powder.

[0035] Comparative Example 1

[0036] This comparative example provides a highly thermally stable blue-green germanate phosphor, the preparation method of which includes:

[0037] (1) Using the preparation of 0.0015 mol sample as the standard, calculate the mass of the corresponding raw materials according to the stoichiometric ratio of each element of the target product, and then weigh them accurately using an electronic balance: according to the chemical composition Ba-Mg-Ge-O, weigh Ba2CO3, MgO and GeO2 respectively, with a molar ratio of 2:1:2; that is, weigh 1.1842 g of Ba2CO3, 0.1209 g of MgO and 0.6278 g of GeO2;

[0038] (2) Place the weighed raw material powder in an agate mortar and grind it for 45 minutes.

[0039] (3) Transfer the alumina crucible containing the mixture to a high-temperature muffle furnace for sintering: the sintering parameters and subsequent treatment are the same as in Example 1.

[0040] Comparative Example 2

[0041] This comparative example provides a highly thermally stable blue-green germanate phosphor, the preparation method of which includes:

[0042] (1) Using the preparation of 0.0015 mol of sample as a standard, calculate the mass of the corresponding raw materials according to the stoichiometric ratio of each element in the target product, and then weigh them accurately using an electronic balance: according to the chemical composition Ba-Mg-Ge-O-Bi, weigh BBa2CO3, MgO, GeO2 and Bi2O3 respectively, with a molar ratio of 1.96:1:2:0.02. That is, weigh 1.1605 g of Ba2CO3, 0.1209 g of MgO, 0.6278 g of GeO2 and 0.0140 g of Bi2O3;

[0043] (2) Place the weighed raw material powder in an agate mortar and grind it for 45 minutes.

[0044] (3) The alumina crucible containing the mixture was transferred to a high-temperature muffle furnace for sintering. The sintering parameters and subsequent treatments were the same as in Example 1.

[0045] Comparative Example 3

[0046] This comparative example provides a highly thermally stable blue-green germanate phosphor, the preparation method of which includes:

[0047] (1) Using the preparation of 0.0015 mol of sample as the standard, calculate the mass of the corresponding raw materials according to the stoichiometric ratio of each element in the target product, and then accurately weigh them using an electronic balance: according to the chemical composition Ba-Mg-Ge-O-Bi, weigh Ba2CO3, MgO, GeO2 and Bi2O3 respectively, with a molar ratio of 1.94:1:2:0.03. That is, weigh 1.1486 g of Ba2CO3, 0.1209 g of MgO, 0.6278 g of GeO2 and 0.0210 g of Bi2O3.

[0048] (2) Place the weighed raw material powder in an agate mortar and grind it for 45 minutes.

[0049] (3) The alumina crucible containing the mixture was transferred to a high-temperature muffle furnace for sintering. The sintering parameters and subsequent treatment were the same as in Example 1.

[0050] Comparative Example 4

[0051] This comparative example provides a highly thermally stable blue-green germanate phosphor, the preparation method of which includes:

[0052] (1) Using the preparation of 0.0015 mol of sample as a standard, calculate the mass of the corresponding raw materials according to the stoichiometric ratio of each element in the target product, and then weigh them accurately using an electronic balance: according to the chemical composition Ba-Mg-Ge-O-Bi, weigh Ba2CO3, MgO, GeO2 and Bi2O3 respectively, with a molar ratio of 1.98:1:2:0.01. That is, weigh 1.1726 g of Ba2CO3, 0.1209 g of MgO, 0.6278 g of GeO2 and 0.0070 g of Bi2O3;

[0053] (2) Place the weighed raw material powder in an agate mortar and grind it for 45 minutes.

[0054] (3) Transfer the alumina crucible containing the mixture to a high-temperature muffle furnace for sintering: raise the temperature to 1000℃ in an air atmosphere at a heating rate of 5℃ / min, hold for 6h, lower the temperature to 500℃ at a cooling rate of 5℃ / min, and then let it cool naturally to room temperature. Take it out and grind it again until there is no obvious particle feel, and obtain the fluorescent powder.

[0055] Experimental Example 1

[0056] The phosphor samples prepared in Example 1 and Comparative Examples 2-4 were subjected to X-ray diffraction, excitation and emission spectra tests.

[0057] (1) X-ray diffraction test: The DX-2700 BH from Dandong Haoyuan Instrument Co., Ltd. was used. The X-ray source was a Cu Kα target, the tube voltage was 40 kV, the tube current was 30 mA, and the scanning range was 10. O -90 O The scanning time was 0.02 seconds, and the scanning step size was 0.03 seconds. O ;

[0058] (2) Excitation and emission spectra were tested: an Edinburgh FLS-920 fluorescence spectrometer was used, with a 450W xenon lamp as the light source and a Hamamatsu R928P photomultiplier tube as the detector. The scanning step size was set to 1 nm, and the excitation and emission slits were both set to 0.4 nm. The excitation wavelength was 362 nm and the emission wavelength was 498 nm.

[0059] (3) Emission and excitation spectra at different temperatures: An Edinburgh FLS-920 fluorescence spectrometer equipped with a temperature control device was used. The temperature control device was assembled by ourselves. The scanning step size was 1 nm and the excitation wavelength was 362 nm. The method is as follows:

[0060] The sample was loaded into an Edinburgh FLS-920 fluorescence spectrometer equipped with a temperature control device connected to a computer. Temperature settings and heating rate parameters were configured using specialized software on this computer. The initial temperature was set to 10°C. o C, temperature range set to 25 o C is a temperature point, meaning the next temperature point is 35. o C, up to 460 o C ends, heating rate is 20 o C / min; hold at each temperature point for three minutes to ensure that the temperature in the sample chamber is consistent with the set temperature; after holding, use an Edinburgh FLS-920 fluorescence spectrometer to test the emission spectrum of the sample and obtain the luminescence intensity curves at different temperatures.

[0061] The performance results of the relevant samples obtained through the above characterization are as follows: Figure 1-4 As shown.

[0062] in, Figure 1 The X-ray diffraction (XRD) spectra of the phosphors provided in Example 1 and Comparative Examples 1-4 are compared: the diffraction peak positions of the main samples (Example 1 and Comparative Examples 1-3) match well with the standard PDF cards, and the crystal phase composition is clear; abnormal impurity peaks were observed at 25° and 29° in Comparative Example 4, indicating the presence of a second phase in the product at this sintering temperature. The spectra of Example 1 and Comparative Examples 1-3 match well with the standard PDF cards, and there are no obvious impurity phases, confirming that the target phase product with high crystallinity was successfully prepared under the above conditions.

[0063] Figure 2 The excitation and emission spectra of the phosphors provided in Example 1 and Comparative Examples 1-3 are presented. The results show that after adding bismuth doping, the luminescence intensity of the examples is significantly improved compared to Comparative Example 1 without bismuth doping; the main peak of the emission spectra of all examples is stably located at 498 nm, clearly characterizing their blue-green light emission properties. Notably, the overlap region between the excitation and emission spectra of Example 1 and Comparative Examples 2-3 is close to zero, fundamentally avoiding spectral reabsorption; simultaneously, a strong absorption band is displayed in the 300-400 nm ultraviolet region, confirming its broad-spectrum ultraviolet excitation capability. Particularly important is that the emission band of this material covers the 400-750 nm visible light region.

[0064] Figure 3 The graph shows the luminescence intensity of the phosphors provided in Example 1 and Comparative Examples 1-3 as a function of temperature. At a high temperature of 160°C, the luminescence intensity retention rate of the phosphor provided in Example 1 is 10%. o Under temperature C, the efficiency was 87.38%, while Comparative Examples 1, 2, and 3 reached 85.87%, 81.49%, and 79.41%, respectively. When the temperature rose to the extreme temperature of 460°C, Example 1 still maintained excellent performance of 63.23%, while the intensity of Comparative Example 1 decreased sharply to 39.19%, the intensity of Comparative Example 2 decreased to 46.41%, and the intensity of Comparative Example 3 decreased to 20.92%. This shows that the phosphor system provided by Example 1 of the present invention not only exhibits excellent thermal stability over a wide temperature range, but also significantly enhances thermal stability while improving luminous efficiency.

[0065] Figure 4 These are photographs of the phosphor provided in Example 1 under ultraviolet light irradiation at different temperatures. Figure 4 It can be clearly seen that as the temperature rises, the luminescence color of the phosphor provided in Example 1 gradually changes from blue-green to blue, and it still has good luminescence intensity at 460℃, proving that the phosphor provided in Example 1 has the ability to adjust the luminescence with temperature and has excellent thermal stability.

[0066] In summary, the high thermal stability blue-green germanate phosphor provided by this invention, synthesized using a novel bismuth-doped germanate phosphor matrix in an ambient air atmosphere via a traditional high-temperature solid-state method, not only simplifies the synthesis process but also produces samples with broad absorption in the ultraviolet region and no overlap between excitation and emission spectra, effectively avoiding spectral reabsorption. Furthermore, it can fill the missing blue-green light region in white LEDs and matches well with existing commercial 365nm near-ultraviolet LED chips. This solves the problem that most phosphor systems cannot maintain excellent luminescence performance at temperatures above 200°C, and can be applied to the preparation of high-quality white LEDs such as ultraviolet chip white LEDs and ultraviolet chip full-spectrum LEDs.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A blue-green germanate phosphor with high thermal stability, characterized in that: Its chemical composition formula is: Ba 1.98 MgGe2O7:0.01Bi 3+ .

2. The high thermal stability blue-green germanate phosphor according to claim 1, characterized in that: The blue-green germanate phosphor emits light in the 480-520nm blue-green band.

3. A method for preparing a high thermal stability blue-green germanate phosphor according to claim 1 or 2, characterized in that: include: (1) Weigh out the raw material powders of Ba2CO3, MgO, GeO2 and Bi2O3 respectively according to the molar ratio of 1.98:1:2:0.01; (2) Place the weighed raw material powder in an agate mortar and grind it. After grinding, a mixture is obtained. Pour the mixture into a clean alumina crucible. (3) The alumina crucible containing the mixture is transferred to a high-temperature muffle furnace for sintering to obtain the phosphor.

4. The method for preparing the high thermal stability blue-green germanate phosphor according to claim 3, characterized in that: The grinding time is 45 minutes.

5. The method for preparing the high thermal stability blue-green germanate phosphor according to claim 3, characterized in that: Sintering conditions include: raising the temperature to 1100°C in an air atmosphere. o C, keep warm for 6 hours, then cool down to 500°C. o C, then allowed to cool naturally to room temperature, removed and ground again to obtain the high thermal stability blue-green germanate phosphor.

6. The method for preparing the high thermal stability blue-green germanate phosphor according to claim 5, characterized in that: The heating rate is 5 o C / min, cooling rate is 5 o C / min.

7. The application of the high thermal stability blue-green germanate phosphor as described in claim 1 or 2 in the preparation of ultraviolet chip white LEDs and ultraviolet chip full-spectrum LEDs.

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