A bismuth-doped germanate-based luminescent tunable material, a preparation method and applications thereof

Abstract

This application provides a bismuth-doped germanate-based tunable luminescent material, its preparation method, and its application, addressing the problem that existing phosphor systems cannot simultaneously cover ultraviolet and blue-green light emission, belonging to the field of luminescent materials technology. The tunable luminescent material has the general chemical formula: Sr a Ba b The concentration of MgGe₂O₇·c mol% Bi is used, where a ranges from 0.1 to 1.2, b ranges from 0.8 to 1.9, and a + b = 2; c ranges from 0.005 to 0.02. This application achieves continuous control of the emission peak position within the 350-550 nm range by continuously adjusting the strontium-barium ratio to form a solid solution in the MgGe₂O₇ matrix, effectively filling the gap in the blue-green region of existing LED spectra. 3+ of 1 S0→ 3 The P1 transition is a spin-allowed broadband absorption with a full width at half maximum (FWHM) typically greater than 100 nm. It can efficiently utilize near-ultraviolet to blue light excitation, avoiding the light leakage problem caused by narrow-band excitation of rare-earth ions.

Description

Technical Field

[0001] This application belongs to the field of luminescent materials technology, specifically relating to a bismuth-doped germanate-based luminescent tunable material, its preparation method, and its application. Background Technology

[0002] Currently, light-emitting diodes (LEDs) have become the mainstream lighting technology due to their advantages such as high efficiency and long lifespan. Commercial white LEDs generally use a scheme where a blue LED chip excites a yellow phosphor, that is, Ce is coated onto a blue LED chip (440-470 nm). 3+ Doped yttrium aluminum garnet (YAG:Ce 3+ This system suffers from a low color rendering index and high color temperature due to the lack of red light components, and its emission spectrum exhibits a significant "gap" in the blue-green light band. Furthermore, it lacks ultraviolet radiation, while ultraviolet light plays a crucial role in sterilization, promoting vitamin D synthesis, and preventing rickets and osteoporosis. Therefore, developing novel phosphors that can simultaneously supplement both the ultraviolet and blue-green light regions is of great significance for achieving full-spectrum healthy lighting.

[0003] In luminescent material systems, rare earth ion-doped materials have long held a dominant position. Rare earth ions, with their rich energy level structures and diverse electronic transition mechanisms, can achieve luminescence from the ultraviolet to the infrared, exhibiting high color purity and stable excitation / emission peak characteristics. However, these materials have significant drawbacks: firstly, rare earth resources are non-renewable, and their mining and smelting processes involve severe resource consumption and environmental burden; secondly, some rare earth ions (such as Eu)... 3+ Yb 3+ Er 3+ The ff transition of rare earth ions exhibits forbidden characteristics, with emission bands mostly being sharp and narrow, making it difficult to achieve broadband continuous spectrum output. Furthermore, their excitation peak positions are fixed, resulting in insufficient absorption of excitation light and a tendency for excitation light leakage, leading to low luminous efficiency. In contrast, broadband-emitting rare earth ions (such as Eu)... 2+ Ce 3+ Although spectral tuning can be achieved to a certain extent through component control, its tuning range remains limited and cannot meet the broadband continuous emission requirements of full-spectrum illumination. Transition metal ions (such as Cr) 3+ Mn 4+ Ni 2+ Doped systems (such as those containing α, β, etc.) exhibit strong broadband absorption characteristics in the ultraviolet-visible region, and their near-infrared emission shows great potential in fields such as bioimaging. However, these materials pose a risk of biotoxicity, and the excitation and emission spectra often overlap, leading to self-absorption effects, which limits their practical application performance.

[0004] In summary, developing a luminescent system that can simultaneously fill the emission gaps in the ultraviolet and blue-green light bands, and overcoming the shortcomings of existing rare earth and transition metal materials in terms of resource sustainability, spectral tunability, and biosafety, has become an urgent technical challenge. Summary of the Invention

[0005] In view of this, this application provides a bismuth-doped germanate-based tunable light-emitting material, its preparation method and application, to solve the problem that existing phosphor systems cannot simultaneously cover ultraviolet and blue-green light emission.

[0006] To solve the above problems, the technical solution adopted in this application is as follows: Firstly, this application proposes a bismuth-doped germanate-based tunable light-emitting material with the general chemical formula: Sr a Ba b MgGe2O7·c mol% Bi; where a ranges from 0.1 to 1.2, b ranges from 0.8 to 1.9, and a + b = 2; c ranges from 0.005 to 0.02.

[0007] Preferably, the value of c is 0.01.

[0008] Preferably, the molar ratio of a to b is 1.2:0.8, 1.1:0.9, 0.9:1.1, 0.7:1.3, 0.6:1.4, 0.5:1.5, 0.3:1.7, 0.2:1.8 or 0.1:1.9.

[0009] Secondly, this application also proposes a method for preparing bismuth-doped germanate-based tunable light-emitting materials as described in the first aspect, comprising the following steps: Step 1: According to the general chemical formula Sr a Ba b Step 1: Weigh out the stoichiometric ratio of each element in MgGe2O7·c mol% Bi, including strontium source, barium source, magnesium source, germanium source, and bismuth source; Step 2: Grind and mix the weighed raw materials evenly to obtain a mixture; Step 3: Sinter the mixture in an air atmosphere, and obtain a sintered product after cooling; Step 4: Grind the sintered product a second time to obtain the bismuth-doped germanate-based tunable luminescent material.

[0010] Preferably, in step one, the strontium source is selected from at least one of strontium carbonate, strontium oxide, strontium hydroxide, or strontium organic acid; the barium source is selected from at least one of barium carbonate, barium oxide, barium hydroxide, or barium organic acid; the magnesium source is selected from at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, or magnesium organic acid; the germanium source is germanium dioxide; and the bismuth source is selected from at least one of bismuth oxide, bismuth carbonate, or bismuth nitrate.

[0011] Preferably, the grinding time in step two is 30-60 min.

[0012] Preferably, the sintering temperature in step three is 1050-1150℃, and the holding time is 4-8 h.

[0013] Preferably, in step three, the temperature is increased to the sintering temperature at a heating rate of 3-10℃ / min, and after the holding period, the temperature is reduced to 400-600℃ at a cooling rate of 3-10℃ / min, and then naturally cooled to room temperature.

[0014] Preferably, the sintering in step three is carried out using an alumina crucible; and the second grinding in step four is performed until there is no obvious particle texture.

[0015] Thirdly, this application also proposes the application of a bismuth-doped germanate-based luminescent tunable material as described in the first aspect or a luminescent tunable material prepared by the preparation method described in the second aspect in ultraviolet chip full-spectrum LED devices, white LED devices, anti-counterfeiting simulation, or optical information storage.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of this application are: This application achieves solid solution formation in a MgGe2O7 matrix by continuously adjusting the strontium-barium ratio, utilizing Sr 2+ with Ba 2+ Differences in ionic radii cause linear changes in the lattice constant, thus continuously altering the Bi0. 3+ The crystal field strength at the lattice site. 3+ 6s 2 Lone pairs of electrons are extremely sensitive to the crystal field. When the crystal field is enhanced, the emission band shifts to blue, and when it is weakened, it shifts to red, thus enabling continuous tuning of the emission peak position in the range of 350-550 nm. This can effectively fill the gap in the blue-green region of the existing LED spectrum. 3+ of 1 S0→ 3 The P1 transition is a spin-allowed broadband absorption with a full width at half maximum (FWHM) typically greater than 100 nm, allowing for efficient excitation from near-ultraviolet to blue light and avoiding the light leakage problem caused by narrow-band excitation of rare-earth ions. Under a suitable crystal field, single Bi1 3+ It can simultaneously generate dual-band emission of ultraviolet (350-400 nm) and blue-green (450-550 nm) light, respectively corresponding to 3 The P1→1S0 transition and defect or low-energy state emission simultaneously supplement the ultraviolet portion of the solar spectrum (which has bactericidal and vitamin D synthesis-promoting functions) and the blue-green portion missing in the LED spectrum, providing a key material for achieving full-spectrum healthy lighting. The matrix utilizes a stable germanate framework with high thermal stability and Bi... 3+During doping, unequal charge levels can introduce cation or oxygen vacancies, which helps regulate the local environment, enhance luminescence efficiency, and suppress thermal quenching. Controlling the doping concentration within a low range of 0.005-0.02 mol% effectively avoids concentration quenching and ensures maximum luminescence intensity. The raw material does not rely on rare earth strategic resources; bismuth is abundant in the Earth's crust, inexpensive, and free from heavy metal toxicity risks, avoiding the environmental burden of rare earth mining and smelting. The emission spectrum of this material is similar to that of commercial YAG:Ce. 3+ The phosphors form complementary emission bands, and when combined, they can easily produce solar-like white LEDs with high color rendering index and adjustable color temperature. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The X-ray diffraction patterns are those of Comparative Example 1 and Examples 1-9 of this application; Figure 2 The excitation spectrum (left) and emission spectrum (right) of Comparative Example 1 and Examples 1-9 of this application are shown in the following figures. (Excitation and emission spectra are not two isolated data; they together describe the complete photophysical process of a fluorescent substance. Combining them in one figure can most intuitively and effectively show the intrinsic relationship and key differences between them, so they are combined in the same figure.) Figure 3 The emission spectra of Embodiment 5 of this application are shown at different excitation wavelengths. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In this application, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and do not limit the number of objects; for example, a first object can be one or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0023] Current commercial white LEDs generally use a scheme where a blue LED chip excites a yellow phosphor, that is, Ce is coated on a blue LED chip (440-470 nm). 3+ Doped yttrium aluminum garnet (YAG:Ce 3+ This system suffers from a low color rendering index and high color temperature due to the lack of red light components, and its emission spectrum exhibits a significant "gap" in the blue-green light band. Furthermore, it lacks ultraviolet radiation, while ultraviolet light plays a crucial role in sterilization, promoting vitamin D synthesis, and preventing rickets and osteoporosis. Therefore, developing novel phosphors that can simultaneously supplement both the ultraviolet and blue-green light regions is of great significance for achieving full-spectrum healthy lighting.

[0024] In luminescent material systems, rare earth ion-doped materials have long held a dominant position. Rare earth ions, with their rich energy level structures and diverse electronic transition mechanisms, can achieve luminescence from the ultraviolet to the infrared, exhibiting high color purity and stable excitation / emission peak characteristics. However, these materials have significant drawbacks: firstly, rare earth resources are non-renewable, and their mining and smelting processes involve severe resource consumption and environmental burden; secondly, some rare earth ions (such as Eu)... 3+ Yb 3+ Er 3+ The ff transition of rare earth ions exhibits forbidden characteristics, with emission bands mostly being sharp and narrow, making it difficult to achieve broadband continuous spectrum output. Furthermore, their excitation peak positions are fixed, resulting in insufficient absorption of excitation light and a tendency for excitation light leakage, leading to low luminous efficiency. In contrast, broadband-emitting rare earth ions (such as Eu)... 2+ Ce 3+ Although spectral tuning can be achieved to a certain extent through component control, its tuning range remains limited and cannot meet the broadband continuous emission requirements of full-spectrum illumination. Transition metal ions (such as Cr) 3+ Mn 4+ Ni 2+ Doped systems (such as those containing α, β, etc.) exhibit strong broadband absorption characteristics in the ultraviolet-visible region, and their near-infrared emission shows great potential in fields such as bioimaging. However, these materials pose a risk of biotoxicity, and the excitation and emission spectra often overlap, leading to self-absorption effects, which limits their practical application performance.

[0025] This application achieves solid solution formation in a MgGe2O7 matrix by continuously adjusting the strontium-barium ratio, utilizing Sr 2+ with Ba 2+ Differences in ionic radii cause linear changes in the lattice constant, thus continuously altering the Bi0. 3+ The crystal field strength at the lattice site. 3+ 6s 2 Lone pairs of electrons are extremely sensitive to the crystal field. When the crystal field is enhanced, the emission band shifts to blue, and when it is weakened, it shifts to red, thus enabling continuous tuning of the emission peak position in the range of 350-550 nm. This can effectively fill the gap in the blue-green region of the existing LED spectrum. 3+ of 1 S0→ 3 The P1 transition is a spin-allowed broadband absorption with a full width at half maximum (FWHM) typically greater than 100 nm, allowing for efficient excitation from near-ultraviolet to blue light and avoiding the light leakage problem caused by narrow-band excitation of rare-earth ions. Under a suitable crystal field, single Bi1 3+ It can simultaneously generate dual-band emission of ultraviolet (350-400 nm) and blue-green (450-550 nm) light, respectively corresponding to 3The P1→1S0 transition and defect or low-energy state emission simultaneously supplement the ultraviolet portion of the solar spectrum (which has bactericidal and vitamin D synthesis-promoting functions) and the blue-green portion missing in the LED spectrum, providing a key material for achieving full-spectrum healthy lighting. The matrix utilizes a stable germanate framework with high thermal stability and Bi... 3+ During doping, unequal charge levels can introduce cation or oxygen vacancies, which helps regulate the local environment, enhance luminescence efficiency, and suppress thermal quenching. Controlling the doping concentration within a low range of 0.005-0.02 mol% effectively avoids concentration quenching and ensures maximum luminescence intensity. The raw material does not rely on rare earth strategic resources; bismuth is abundant in the Earth's crust, inexpensive, and free from heavy metal toxicity risks, avoiding the environmental burden of rare earth mining and smelting. The emission spectrum of this material is similar to that of commercial YAG:Ce. 3+ The phosphors form complementary emission bands, and when combined, they can easily produce solar-like white LEDs with high color rendering index and adjustable color temperature.

[0026] The following is in conjunction with the appendix Figures 1 to 3 The technical solutions provided in this application will be described in detail through specific embodiments and application scenarios.

[0027] Firstly, this application proposes a bismuth-doped germanate-based tunable light-emitting material with the general chemical formula: Sr a Ba b MgGe2O7·c mol% Bi; where a ranges from 0.1 to 1.2, b ranges from 0.8 to 1.9, and a + b = 2; c ranges from 0.005 to 0.02.

[0028] Sr 2+ with Ba 2+ Ion radius difference (Sr 2+ ≈1.18 Å, Ba 2+ The Sr / Ba ratio (≈1.35 Å) allows for the formation of a continuous solid solution in the MgGe2O7 matrix. The lattice constant changes linearly with the Sr / Ba ratio, leading to a change in Bi... 3+ The crystal field intensity at the lattice site changes continuously. 3+ of 6 s 2 Lone pairs of electrons are extremely sensitive to the crystal field. When the crystal field is enhanced, the energy level splitting of their excited state increases, and the emission band shifts towards shorter wavelengths. When the crystal field is weakened, the emission band redshifts. By adjusting the values ​​of a and b, the emission peak position can be continuously tuned in the range of 350-550 nm, covering the ultraviolet (UVA) and blue-green light bands, filling the "gap" in the blue-green region of the existing LED spectrum.

[0029] Bismuth ions 1 S0→ 3The P1 transition is a spin-allowed broadband absorption (typically > 100 nm), which can efficiently utilize near-ultraviolet to blue light excitation, avoiding the light leakage problem caused by narrow-band excitation of rare-earth ions. Under a suitable crystal field, a single bismuth ion can simultaneously generate two emission bands: ultraviolet (350-400 nm) and blue-green (450-550 nm), corresponding to... 3 The P1→1S0 transition and emission from defects or low-energy states. This single-ion dual-band emission characteristic allows the material to simultaneously supplement the ultraviolet portion of the solar spectrum (for sterilization and promoting vitamin D synthesis) and the blue-green portion missing from the LED spectrum, achieving full-spectrum healthy lighting.

[0030] The MgGe2O7 matrix employs a stable germanate framework with high thermal stability. Bismuth ion doping introduces cation or oxygen vacancies due to charge inequality, which helps regulate the local environment, enhance luminous efficiency, and suppress thermal quenching. Controlling the doping concentration within a low range of 0.005-0.02 mol% avoids concentration quenching and ensures maximum luminous intensity. The raw materials do not rely on rare earth strategic resources; bismuth is abundant in the Earth's crust, inexpensive, and free from heavy metal toxicity concerns, avoiding the environmental burden of rare earth mining and smelting. The emission spectrum is well-complementary to the emission band of commercially available yttrium aluminum garnet:cerium phosphor, making it easy to obtain a high color rendering index, tunable color temperature, and sunlight-like white light-emitting diode.

[0031] Furthermore, the value of c is 0.01. At this doping concentration, Bi 3+ The ions are distributed in an isolated, single-center pattern within the matrix, with a moderate average distance between the luminescent centers. This ensures that a sufficient number of activated ions participate in the luminescence process to achieve a high absolute luminescence intensity, while effectively avoiding concentration quenching caused by cross-relaxation or energy migration due to excessively high doping concentration. This concentration is precisely within the range of Bi... 3+ Within the optimal luminescence concentration range of the germanate matrix, efficient transfer of excitation light energy to the luminescence center can be achieved while maintaining the integrity of the crystal field environment, preventing lattice distortion or defect quenching centers due to excessive impurities. From an electronic structure perspective, Bi... 3+ 6s 2 At this concentration, the lone pair electrons are subject to moderate perturbation by neighboring coordinating ions. 3 P1 Excited State Energy Level and Ground State 1 The transition probability between S0 and S0 is the highest, resulting in an optimal match between absorption cross-section and quantum efficiency. Furthermore, the low doping concentration of 0.01% helps maintain the intrinsic thermal stability of the matrix, avoiding the thermal quenching temperature drop that may be caused by high doping concentrations, and ensuring that the phosphor maintains stable luminescence output at the operating temperature of the LED chip.

[0032] Furthermore, the molar ratio of a to b is 1.2:0.8, 1.1:0.9, 0.9:1.1, 0.7:1.3, 0.6:1.4, 0.5:1.5, 0.3:1.7, 0.2:1.8, or 0.1:1.9. These specific ratio points cover the complete solid solution composition range from strontium-rich to barium-rich, and each ratio point corresponds to a specific lattice constant and crystal field intensity, thereby realizing Bi 3+ Fine-tuning and continuous control of the emission spectrum. When the strontium content is high (e.g., 1.2:0.8, 1.1:0.9), the smaller Sr... 2+ The radius enhances lattice contraction, Bi 3+ The increased crystal field strength at the lattice site intensifies the 5d level splitting, shifting the emission band towards shorter wavelengths, with the main peak located in the ultraviolet to near-ultraviolet region (approximately 350-380 nm). As the barium content gradually increases (e.g., 0.9:1.1, 0.7:1.3), lattice expansion weakens the crystal field, causing a redshift in the emission band, gradually covering the blue light region (approximately 420-470 nm). When the barium content further increases to the barium-rich end (e.g., 0.1:1.9), the crystal field strength drops to its minimum, and the emission band extends into the blue-green region (approximately 500-550 nm). These specific ratio points not only verify the effectiveness of continuous Sr / Ba substitution for spectral tuning, but each ratio point has also been experimentally verified, yielding phosphor samples with a single phase, good crystallinity, and excellent luminescence performance. From an electronic structure mechanism analysis, Bi... 3+ 6s 2 The electron cloud expands to different degrees under different crystal field intensities, causing a regular shift in the centroid of its excited state energy levels. These proportional points precisely correspond to characteristic inflection points on the spectral tuning curve, enabling the coverage of the entire emission band with fewer compositional points. This provides a precise material library for the selective filling of gaps in different bands of full-spectrum illumination. Furthermore, the solid solution formation energy at these proportions is low, making it easy to obtain a pure phase through high-temperature solid-state methods. This avoids the potential for impurities or phase separation due to excessive compositional deviations, ensuring batch stability and application reliability of the materials.

[0033] Secondly, this application also proposes a method for preparing a bismuth-doped germanate-based tunable light-emitting material as described in the first aspect, comprising the following steps: Step 1: According to the general chemical formula Sr a Ba bThe stoichiometric ratio of each element in MgGe2O7·c mol% Bi is determined by weighing out the strontium source, barium source, magnesium source, germanium source, and bismuth source; the strontium source is selected from at least one of strontium carbonate, strontium oxide, strontium hydroxide, or strontium organic acid; the barium source is selected from at least one of barium carbonate, barium oxide, barium hydroxide, or barium organic acid; the magnesium source is selected from at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, or magnesium organic acid; the germanium source is germanium dioxide; and the bismuth source is selected from at least one of bismuth oxide, bismuth carbonate, or bismuth nitrate.

[0034] Step 2: Grind the weighed raw materials for 30-60 minutes and mix them evenly to obtain a mixture. Step 3: Place the mixture in an alumina crucible and sinter it in an air atmosphere. Raise the temperature to the sintering temperature at a rate of 3-10℃ / min. The sintering temperature is 1050-1150℃. Hold the temperature for 4-8 hours. After holding, lower the temperature to 400-600℃ at a rate of 3-10℃ / min. Then, allow it to cool naturally to room temperature to obtain the sintered product. Step 4: The sintered product is ground a second time until there is no obvious particle texture to obtain the bismuth-doped germanate-based luminescent tunable material.

[0035] Using carbonates, oxides, or organic acid salts as strontium, barium, magnesium, and bismuth sources, and germanium dioxide as a germanium source, these raw materials can all decompose into their corresponding oxides at high temperatures, exhibiting strong driving forces for solid-phase reactions. Furthermore, the raw materials are widely available, inexpensive, and do not rely on high-purity rare earth elements or scarce metals, thus possessing good industrial applicability and economic viability. The broadened range of raw material selection covers a variety of commonly used precursors, making the method not limited to specific chemicals and enhancing the process's flexibility and substitutability.

[0036] The grinding time is controlled between 30 and 60 minutes. This can activate the powder surface through mechanical force, shorten the ion diffusion path, and enable the components to achieve uniform mixing at the microscale. It can also avoid introducing too many impurities or causing powder agglomeration due to excessive grinding, thereby ensuring the uniformity and completeness of the subsequent solid-phase reaction.

[0037] The sintering temperature was set at 1050 to 1150℃, with a holding time of 4 to 8 hours. This temperature range satisfies the phase formation requirements of the germanate matrix, allowing Sr / Ba / Mg / Ge elements to fully diffuse and form a continuous solid solution, while avoiding excessively high temperatures or prolonged holding times that could lead to excessively coarse grains or bismuth ion volatilization loss. Under these conditions, Bi... 3+ Able to effectively enter the lattice and occupy Sr 2+ / Ba 2+ The formation of lattice sites, along with the creation of an appropriate number of cation vacancies to maintain charge balance, is beneficial for the stable existence of luminescent centers and the improvement of luminescence efficiency.

[0038] Using a heating and cooling rate of 3 to 10 °C / min, with the temperature first reduced at the same rate to 400 to 600 °C before natural cooling, this segmented cooling regime can control the formation and distribution of defects during cooling, reduce internal stress and lattice distortion caused by rapid cooling, and help obtain phosphors with complete crystal structure, suitable defect types, and stable luminescence properties. Sintering in an air atmosphere can maintain Bi 3+ The +3 valence state is used to avoid luminescence deactivation caused by the precipitation of metallic bismuth or changes in valence state that may occur under a reducing atmosphere.

[0039] Using an alumina crucible as the sintering container offers advantages such as high chemical inertness and high-temperature resistance. It does not react significantly with the germanate matrix at around 1100℃, preventing the introduction of impurities or quenching centers due to container contamination. Secondary grinding until no noticeable particles remain disperses the slight agglomerates formed after sintering into fine powder, resulting in uniform particle size and good dispersibility. This facilitates subsequent coating applications in light-emitting devices while ensuring the density and uniformity of the light-emitting layer, thus improving the device's light extraction efficiency.

[0040] The entire preparation method is based on the traditional high-temperature solid-state method. The equipment used is conventional laboratory and industrial equipment such as muffle furnace and agate mortar. It does not require vacuum, atmosphere protection or special sintering equipment. It has a wide process window, is easy to operate, has good reproducibility, and is easy to directly transform from laboratory pilot to large-scale production.

[0041] Thirdly, this application also proposes the application of a bismuth-doped germanate-based luminescent tunable material as described in the first aspect or a luminescent tunable material prepared by the preparation method described in the second aspect in ultraviolet chip full-spectrum LED devices, white LED devices, anti-counterfeiting simulation, or optical information storage.

[0042] Example 1

[0043] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba bMgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=1.2:0.8:1:2:0.01. The raw materials were weighed according to this molar ratio. To reduce experimental error, the weighing result was controlled to have an error of ±0.3 mg compared to the calculated result. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. The alumina crucible containing the mixture was transferred to a high-temperature muffle furnace for sintering. The sintering was carried out in an air atmosphere at 5... o The heating rate of C / min will raise the temperature to 1100. o C, keep warm for 6 hours, with 5 o The cooling rate decreased to 500 °C / min. o C, then let it cool naturally to room temperature, take it out and grind it again until there is no obvious particle feel, to obtain the fluorescent powder.

[0044] Example 2

[0045] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba b MgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=1.1:0.9:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0046] Example 3

[0047] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba bMgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.9:1.1:1:2:0.01. The raw materials were weighed out according to the molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0048] Example 4

[0049] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba b MgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.7:1.3:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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] Example 5

[0051] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba bMgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.6:1.4:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0052] Example 6

[0053] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba b MgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.5:1.5:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0054] Example 7

[0055] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba bMgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.3:1.7:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0056] Example 8

[0057] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba b MgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.2:1.8:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0058] Example 9

[0059] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba bMgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=0.1:1.9:1:2:0.01. The raw materials were weighed according to this molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0060] Comparative Example 1

[0061] Using a 0.0025 mol sample as a standard, the mass of the corresponding raw materials was calculated according to the stoichiometric ratio of each element in the target product, and then accurately weighed using an electronic balance. All chemical reagents were used directly in the preparation process without additional purification, drying, or synthesis. According to the chemical composition Sr... a Ba b MgGe2O7: cmol%Bi, where a+b=2, c=0.01. Sr2CO3, Ba2CO3, MgO, GeO2, and Bi2O3 were weighed out separately, with an elemental molar ratio of Sr:Ba:Mg:Ge:O:Bi=2:0:1:2:0.01, meaning no Ba ion substitution was performed on Sr. The raw materials were weighed according to the molar ratio. The weighed raw material powder was placed in an agate mortar and ground for 45 minutes to ensure thorough and uniform mixing. 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.

[0062] The phosphor samples prepared above were subjected to X-ray diffraction testing using a DX-2700 BH instrument from Dandong Haoyuan Instrument Co., Ltd. The X-ray source was a Cu Kα target, the tube voltage was 40 kV, the tube current was 30 mA, the scanning range was 10–90°, the scanning time was 0.02 s, and the scanning step size was 0.03°. Excitation and emission spectra were measured using a Hitachi F-7000 fluorescence spectrophotometer, with a 150W xenon lamp as the excitation source. The instrument voltage and response time were uniformly set to 700 V and 0.1 s, respectively, and the scanning speed was 240 nm / min. The performance results of the relevant samples were obtained through the above characterization.

[0063] Characterization results

[0064] Figure 1 The X-ray diffraction patterns of Comparative Example 1 and Examples 1-9 show that the diffraction peak positions match well with the target phase standard card, and no impurity peaks appear, confirming the acquisition of a single phase. With Ba2+ With increasing substitution, the characteristic diffraction peaks systematically shift towards smaller angles. Based on the Bragg equation, the interplanar spacing increases, which is attributed to the large radius Ba... 2+ Replace small radius Sr 2+ This leads to cell expansion. This chain of evidence collectively verifies the effectiveness of component substitution and the purity of the product phase.

[0065] Figure 2 The excitation (left) and emission (right) spectra of Comparative Example 1 and Examples 1-9 are shown. With Ba 2+ With increasing substitution, the excitation spectrum peak position gradually redshifts, and its full width at half maximum (FWHM) also gradually broadens, with the excitation peak position redshifting from 303 nm to 353 nm. For example... Figure 3 As shown in the emission spectrum, at the same excitation wavelength, with Ba 2+ With increasing substitution, the relative intensity of the emission peaks exhibits a fluctuating trend, with the relative intensity of the emission peak in the 460 nm blue-green region gradually increasing until the substitution ratio reaches Sr:Ba = 0.3:1.7. At this point, the emission peak in the 360 ​​nm ultraviolet region disappears, achieving spectral tuning of approximately 100 nm. When the substitution ratio is Sr:Ba = 0.5:1.5, emission peaks appear simultaneously in both the 360 ​​nm ultraviolet and 460 nm blue-green regions, resulting in a continuous emission spectrum within the 320-600 nm range, spanning from the ultraviolet to the visible light region. This allows for the simultaneous supplementation of both the ultraviolet and blue-green regions in full-spectrum LEDs. These data demonstrate that this series of materials possesses excellent luminescence tunability, providing material support for healthy lighting.

[0066] Figure 3 The figure shows the emission spectra of Example 5 at different excitation wavelengths. As shown, different peak positions can be achieved by changing the excitation wavelength. As the excitation wavelength increases from 290 nm to 330 nm, the emission in the 460 nm blue-green region gradually increases, while the emission in the ultraviolet region first increases and then decreases until it disappears. Therefore, this phosphor system can also be applied to anti-counterfeiting simulation, optical information storage, and other applications.

[0067] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0068] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0070] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

Claims

1. A bismuth-doped germanate-based luminescent tunable material, characterized in that, Its general chemical formula is: Sr a Ba b MgGe2O7• c mol% Bi; Where a ranges from 0.1 to 1.2, b ranges from 0.8 to 1.9, and a + b = 2; c ranges from 0.005 to 0.

02.

2. The bismuth-doped germanate-based luminescent tunable material of claim 1, wherein, The value of c is 0.

01.

3. The bismuth-doped germanate-based luminescent tunable material according to claim 1 or 2, characterized in that The molar ratio of a to b is 1.2:0.8, 1.1:0.9, 0.9:1.1, 0.7:1.3, 0.6:1.4, 0.5:1.5, 0.3:1.7, 0.2:1.8, or 0.1:1.

9.

4. A method for preparing a bismuth-doped germanate-based tunable luminescent material as described in any one of claims 1-3, characterized in that, Includes the following steps: Step one: according to the chemical formula Sr a Ba b MgGe2O7·c mol% Bi The stoichiometric ratio of each element in the source of strontium, barium, magnesium, germanium and bismuth is weighed. Step 2: Grind and mix the weighed raw materials evenly to obtain a mixture. Step 3: Sinter the mixture in air atmosphere, and obtain the sintered product after cooling; Step 4: The sintered product is ground a second time to obtain the bismuth-doped germanate-based luminescent tunable material.

5. The method for preparing bismuth-doped germanate-based tunable luminescent material according to claim 4, characterized in that, In step one, the strontium source is selected from at least one of strontium carbonate, strontium oxide, strontium hydroxide, or strontium organic acid; the barium source is selected from at least one of barium carbonate, barium oxide, barium hydroxide, or barium organic acid; the magnesium source is selected from at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, or magnesium organic acid; the germanium source is germanium dioxide; and the bismuth source is selected from at least one of bismuth oxide, bismuth carbonate, or bismuth nitrate.

6. The method for preparing bismuth-doped germanate-based tunable luminescent material according to claim 4, characterized in that, The grinding time in step two is 30-60 minutes.

7. The method for preparing the bismuth-doped germanate-based tunable light-emitting material according to claim 4, characterized in that, In step three, the sintering temperature is 1050-1150℃, and the holding time is 4-8 hours.

8. The method for preparing the bismuth-doped germanate-based tunable luminescent material according to claim 4, characterized in that, In step three, the temperature is increased to the sintering temperature at a heating rate of 3-10℃ / min. After holding at that temperature, the temperature is reduced to 400-600℃ at a cooling rate of 3-10℃ / min, and then allowed to cool naturally to room temperature.

9. The method for preparing the bismuth-doped germanate-based tunable luminescent material according to claim 4, characterized in that, The sintering in step three uses an alumina crucible; in step four, the material is ground a second time until there is no obvious graininess.

10. The application of a bismuth-doped germanate-based luminescent tunable material as described in any one of claims 1-3 or a luminescent tunable material prepared by the preparation method described in any one of claims 4-9 in ultraviolet chip full-spectrum LED devices, white LED devices, anti-counterfeiting simulation, or optical information storage.

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