Method for preparing narrow-band green fluorescent powder through multi-step sintering and LED package

Abstract

The invention relates to the field of LED luminescent materials, solves the problems of harsh synthesis conditions and high production cost of narrow-band green fluorescent powder in the prior art, and provides a method for preparing narrow-band green fluorescent powder through multi-step sintering and an LED package. The method comprises the following steps: uniformly mixing silicon nitride, aluminum nitride, aluminum oxide and a europium doping source according to a preset proportion to obtain a mixture; controlling a reaction furnace to perform staged sintering on the mixture, wherein the staged sintering at least comprises a high-temperature sintering stage and a low-temperature reduction sintering stage; after sintering is completed, the sintered material is rapidly cooled according to the preset cooling rate and the preset cooling time, and a fluorescent powder sample is obtained; and testing the performance of the fluorescent powder sample, and adjusting sintering parameters according to the deviation between the test result and the target parameter window. According to the invention, the proportion and the luminescence property of divalent Eu ions are improved, the synthesis difficulty and the production cost are reduced, and the method is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of LED light-emitting materials, and more particularly to a method for preparing narrowband green phosphors through multi-step sintering and LED packaging. Background Technology

[0002] Narrow-band green phosphors are widely used in high color gamut displays, laser lighting, and high-end solid-state lighting due to their advantages such as narrow emission spectrum half-maximum width at half-maximum, high color purity, and good matching with blue or violet excitation sources. Among them, β-Sialon:Eu phosphor has outstanding application potential in the existing green phosphor system due to its unique oxynitride crystal structure and Eu²⁺ activated luminescence mechanism.

[0003] However, the synthesis of β-Sialon:Eu phosphors requires extremely stringent sintering conditions. Existing technologies typically require prolonged sintering under high temperature or even high pressure nitriding conditions to ensure sufficient reaction of raw materials such as silicon nitride and aluminum nitride, forming a stable β-Sialon host crystal structure. These processes not only demand sophisticated equipment and consume a lot of energy, but also have high production costs, making it difficult to meet the needs of large-scale production.

[0004] Patent CN104479673B discloses a nitrogen oxide phosphor and its preparation method. The method requires sintering a mixture of raw materials at 1800–2200℃ and 1–200 MPa to achieve crystal phase formation and activation of doped ions.

[0005] However, these methods are highly dependent on extreme sintering conditions. On the one hand, they impose extremely high temperature and pressure resistance requirements on the reactor equipment, necessitating the configuration of high-pressure sintering devices or special protective structures, significantly increasing equipment investment costs and operating energy consumption. On the other hand, under high temperature and pressure conditions, the sintering process has limited room for controlling the occupancy state and valence distribution of dopant ions. Once the process parameters are set, it is difficult to effectively correct them in subsequent processes, making the preparation process highly sensitive to the initial process window. These problems make it difficult for existing technologies to ensure the consistency of luminescence performance while simultaneously achieving equipment versatility and process controllability, thus limiting the large-scale, low-cost preparation of narrowband green phosphors under industrial conditions.

[0006] Therefore, there is an urgent need for a phosphor preparation method that can achieve crystal phase formation at relatively low sintering temperatures and possesses adjustable parameters and feedback control capabilities, in order to reduce dependence on high-temperature and high-pressure equipment and improve the process flexibility and industrial applicability of the preparation process. Summary of the Invention

[0007] In view of this, embodiments of the present invention provide a method for preparing narrowband green phosphors by multi-step sintering and LED packaging, in order to solve the problems of high dependence on high temperature and high pressure sintering conditions and high equipment requirements in the preparation process of narrowband green phosphors in the prior art.

[0008] In a first aspect, embodiments of the present invention provide a method for preparing narrowband green phosphor by multi-step sintering and LED packaging, wherein the narrowband green phosphor is β-Sialon:Eu, and the method includes: The raw materials are uniformly mixed according to a preset ratio to obtain a mixture, wherein the raw materials include silicon nitride, aluminum nitride, aluminum oxide and europium doping source; According to preset sintering parameters, the reactor is controlled to perform staged sintering under a reaction atmosphere to obtain sintered material. The preset sintering parameters include sintering temperature, holding time and gas ratio of the reaction atmosphere. The staged sintering includes at least a first sintering stage and a second sintering stage. The sintering temperature of the first sintering stage is higher than that of the second sintering stage. The sintering temperatures are all below 1800℃. The sintered material is rapidly cooled according to a preset cooling rate and a preset cooling time to obtain a phosphor sample. The phosphor sample was subjected to performance testing to obtain test results, wherein the test results include Eu site distribution, valence state ratio and luminescence performance parameters; Based on the deviation between the test results and the target parameter window, the preset sintering parameters are adjusted. Based on the adjusted preset sintering parameters, return to the step of controlling the reactor to perform staged sintering under the reaction atmosphere to obtain sintered materials, until the test results of the phosphor sample meet the target parameter window.

[0009] Preferably, the step of controlling the reactor to perform staged sintering to obtain sintered materials under a reaction atmosphere and according to preset sintering parameters includes... According to the first sintering parameters, the mixture is sintered at high temperature under the first reaction atmosphere to form the main crystal of the narrow-band green phosphor and obtain the initial sintered material. The first sintering parameters include a first sintering temperature and a first holding time. The first sintering temperature is between 1630 and 1750°C, the first holding time is between 1 and 4 hours, and the first reaction atmosphere is nitrogen or a mixed gas including nitrogen and hydrogen. According to the second sintering parameters, the initial sintering material is subjected to low-temperature reduction sintering under the second reaction atmosphere to promote Eu in the crystal lattice. 3+ To Eu 2+The valence state transformation is used to obtain the final sintered material. The second sintering parameters include a second sintering temperature and a second holding time. The second sintering temperature is lower than the first sintering temperature. The second reaction atmosphere is a mixture of nitrogen and hydrogen. The hydrogen content of the second reaction atmosphere is higher than the hydrogen content of the first reaction stage. The pressures of the first and second reaction atmospheres are between 0.3 and 0.8 MPa.

[0010] Preferably, the second sintering temperature is between 1350-1380℃, the second preset holding time is 20-30 minutes, and the pressure of the first reaction atmosphere and the second reaction atmosphere is 0.4~0.6MPa.

[0011] Preferably, after the initial sintering material is subjected to low-temperature reduction sintering in a second reaction atmosphere according to the second sintering parameters to promote the valence state transformation of Eu3+ to Eu2+ in the crystal lattice and obtain the sintered material, the method further includes: At the end of the second sintering stage, the annealing start temperature is determined based on the real-time temperature and pressure inside the reactor. Under an inert atmosphere or the second reaction atmosphere, the temperature of the reactor is reduced from the annealing start temperature to the preset annealing temperature at a first preset cooling rate, wherein the preset annealing temperature is between 900-1200°C. The material is held at the preset annealing temperature for a third preset time to obtain the final sintered material, wherein the third preset time is between 10 and 20 minutes.

[0012] Preferably, the performance testing of the phosphor sample to obtain test results includes: The phosphor sample was subjected to extended X-ray absorption fine structure (EXAFS) testing to obtain structural characterization information, which included the coordination environment parameters and site distribution parameters of Eu ions in the β-Sialon lattice. X-ray photoelectron spectroscopy (XPS) was performed on the phosphor sample to obtain valence state characterization information, and Eu was obtained. 2+ With Eu 3+ The proportion of price states; The phosphor sample is subjected to luminescence performance testing to obtain luminescence performance parameters, wherein the luminescence performance parameters include at least one of emission peak position, full width at half maximum (FWHM), and external quantum efficiency.

[0013] Preferably, adjusting the preset sintering parameters based on the deviation between the test results and the target parameter window includes: Based on the difference between the test results and the target parameter window, deviation information is obtained, wherein the deviation information includes the deviation direction and the corresponding deviation degree of the fixed structure deviation, valence state deviation and luminescence deviation; The correlation data and cross-influence degree of the preset sintering parameters and the deviation information are obtained, wherein the preset sintering parameters include a first sintering parameter and a second sintering parameter, and the correlation data is used to characterize the relationship between the changes of the preset sintering parameters and the deviation information; Based on the correlation data and the degree of cross-influence, determine the parameters to be adjusted and the locked parameters that will not be adjusted in the preset sintering parameters; Under the condition that the locking parameter remains unchanged, the parameter to be adjusted is adjusted according to the deviation information to obtain the updated preset sintering parameter.

[0014] Preferably, determining the parameters to be adjusted and the locked parameters not to be adjusted in the preset sintering parameters based on the correlation data and the degree of cross-influence includes: Based on the deviations of the structural deviation, the valence state deviation, and the luminescence deviation relative to the target parameter window, the target deviation for the current adjustment cycle is determined. Based on the correlation data, the direction and magnitude of the changes in structural deviation, valence state deviation and luminescence deviation caused by the changes in each preset sintering parameter are determined, and the deviation response characteristics corresponding to each preset sintering parameter are obtained. Based on the degree of cross-influence, the cross-response characteristics corresponding to each preset sintering parameter are obtained by determining whether each preset sintering parameter causes changes in the target deviation and changes in the non-target deviation. Based on the deviation response characteristics, each preset sintering parameter is initially screened, and the preset sintering parameters that can reduce the degree of deviation of the target deviation are determined as candidate adjustment parameters. The cross-response characteristics corresponding to the candidate adjustment parameters are compared. When a candidate adjustment parameter reduces the degree of deviation of the target deviation and at the same time makes the change amplitude of at least two types of non-target deviations reach a preset change threshold, the candidate adjustment parameter is removed from the candidate adjustment parameters and determined as the locked parameter. When multiple candidate adjustment parameters can reduce the degree of deviation of the target deviation and the change in the non-target deviation does not reach the preset change threshold, the candidate adjustment parameter with a cross-influence degree lower than the preset cross-influence degree threshold is determined as the parameter to be adjusted based on the difference in the cross-response characteristics of each candidate adjustment parameter, and the remaining candidate adjustment parameters are determined as locked parameters.

[0015] Preferably, determining the parameters to be adjusted and the locked parameters not to be adjusted in the preset sintering parameters based on the correlation data and the degree of cross-influence includes: Based on the deviations of the structural deviation, the valence state deviation, and the luminescence deviation relative to the target parameter window, the target deviation of the current adjustment cycle is determined, and the priority control thermal process segment corresponding to the target deviation is determined. The priority control thermal process segment includes at least one of the following: a first sintering stage, a second sintering stage, an annealing stage, and a rapid cooling stage. Based on the correlation data, the response relationship of each preset sintering parameter to the target deviation is determined, and the preset sintering parameter corresponding to the priority control thermal history segment is determined as the candidate adjustment parameter. The preset sintering parameter includes at least a first sintering parameter, a second sintering parameter, an annealing parameter, and a cooling parameter. Based on the degree of cross-influence, the degree of coupling influence of the candidate adjustment parameter on at least one type of non-target deviation while improving the target deviation is determined, and the cross-influence characteristics corresponding to the candidate adjustment parameter are obtained. When the cross-influence feature corresponding to a candidate adjustment parameter indicates that its influence on at least two types of non-target deviations reaches a preset influence threshold, the candidate adjustment parameter is determined as a locked parameter and remains unchanged, so as to avoid introducing significant fluctuations in at least two types of non-target deviations during the adjustment of the target deviation. When multiple candidate adjustment parameters can improve the target deviation and their influence on the non-target deviation does not reach the preset influence threshold, the candidate adjustment parameter with a cross-influence degree lower than the preset cross-influence degree threshold is determined as the parameter to be adjusted, and the remaining candidate adjustment parameters are determined as locked parameters.

[0016] Preferably, the step of adjusting the parameter to be adjusted according to the deviation information to obtain the updated preset sintering parameters, under the condition that the locking parameter remains unchanged, includes: Obtain the current parameter value and the corresponding allowable adjustment range of the parameter to be adjusted, and determine the adjustment direction of the parameter to be adjusted based on the deviation direction between the target deviation and the target parameter window; Based on the degree of deviation of the target deviation, the target control amplitude level of the priority control thermal history segment is determined; According to the target amplitude level, the sintering process corresponding to the parameter to be adjusted is adjusted once within the priority control thermal history segment to obtain candidate parameter values, and candidate preset sintering parameters are obtained under the condition that the locked parameters remain unchanged. Sintering is performed based on the candidate preset sintering parameters, and the performance of the resulting phosphor sample is tested to obtain the corresponding candidate test results. Compare the candidate test results with the previous round of test results to determine whether the degree of deviation of the target deviation has decreased; When the degree of deviation of the target deviation decreases, the candidate preset sintering parameters are determined as the updated preset sintering parameters; When the degree of deviation of the target deviation does not decrease or increases in the opposite direction, the locking parameter remains unchanged, and the parameter to be adjusted is rolled back to the parameter value of the previous round.

[0017] Secondly, embodiments of the present invention provide an LED package including an LED light-emitting unit, the LED light-emitting unit including an excitation chip and a phosphor assembly, the phosphor assembly including at least a narrow-band green phosphor prepared by the method described in the first aspect, the high-power LED lighting fixture being used for long-distance lighting applications.

[0018] In summary, the beneficial effects of the present invention are as follows: By implementing a multi-step sintering process under micro-positive pressure, the preparation temperature of β-Sialon:Eu phosphor is controlled below 1800℃, avoiding the dependence on expensive equipment and complex process conditions of traditional high-temperature and high-pressure processes, thus reducing the preparation difficulty. Combining high-temperature sintering with low-temperature reduction sintering, along with controlled atmosphere and rapid cooling, effectively promotes the transformation of trivalent Eu ions to divalent Eu ions while suppressing valence state reversion, increasing the effective number of luminescent centers. The synergistic effect of staged sintering and rapid cooling reduces the risk of uneven Eu ion distribution and phase separation within the crystal lattice, resulting in better batch stability of the obtained phosphor in terms of structure, valence state, and luminescence performance. This invention features a clear process flow and controllable parameters, suitable for implementation on conventional sintering equipment, reducing energy consumption and equipment investment costs, and possessing good potential for large-scale production. By testing the structure, valence state, and luminescence performance, and adjusting the sintering parameters based on the deviation between the test results and the target parameter window, the preparation process has continuous optimization capabilities, facilitating the rapid establishment of a stable process window.

[0019] In summary, the narrow-band green phosphor prepared by the method of the present invention has the characteristics of stable emission peak position, narrow half-width at half-maximum and high luminous efficiency, and is suitable for applications such as high color gamut LED and laser display. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, and these are all within the protection scope of the present invention.

[0021] Figure 1This is a schematic diagram of the method for preparing narrowband green phosphor by multi-step sintering according to an embodiment of the present invention and the process of LED packaging.

[0022] Figure 2 This is another schematic diagram of the method for preparing narrowband green phosphor by multi-step sintering according to an embodiment of the present invention and for LED packaging.

[0023] Figure 3 This is a schematic diagram of another process for preparing narrowband green phosphor by multi-step sintering according to an embodiment of the present invention and for LED packaging. Detailed Implementation

[0024] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0025] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, 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. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0026] Example 1 This invention provides a method for preparing narrowband green phosphor via multi-step sintering and LED packaging, wherein the narrowband green phosphor is β-Sialon:Eu, and the method includes: S1. Mix the raw materials uniformly according to a preset ratio to obtain a mixture, wherein the raw materials include silicon nitride, aluminum nitride, aluminum oxide and europium doping source; Specifically, the preset ratio refers to the proportions of each raw material set to obtain the target β-Sialon:Eu stoichiometry and luminescent center concentration. For example, the molar ratio of Si3N4, AlN, and Al2O3 is determined based on the composition of β-Si6-zAlzOzN8-z:Eu, and the amount of europium doping source added is selected in conjunction with the target Eu doping amount. The europium doping source can be europium oxide Eu2O3 or other compounds that can introduce Eu during sintering.

[0027] Specifically, this can be accomplished by ball milling, planetary grinding, wet dispersion followed by drying, etc. Dispersants can be added to anhydrous organic solvents to inhibit agglomeration, or the powder can be treated in an inert atmosphere or dry environment to reduce the adsorption of water and oxygen by the powder.

[0028] The raw materials are preferably sieved and pre-dried to reduce the uneven reaction caused by large particles and water-containing oxygen components. This step enables the aluminum oxide source and the nitride framework raw material to have sufficient contact at the microscale, and allows the europium doping source to be distributed more uniformly in the potential nucleation and grain growth regions, thereby improving the uniformity of subsequent main crystal formation and the consistency of luminescent center distribution, and reducing the risk of impurity phases and local concentration quenching.

[0029] S2. According to preset sintering parameters, the reactor is controlled to perform staged sintering in a reaction atmosphere to obtain sintered material. The preset sintering parameters include sintering temperature, holding time and gas ratio of the reaction atmosphere. The staged sintering includes at least a first sintering stage and a second sintering stage. The sintering temperature of the first sintering stage is higher than that of the second sintering stage. The sintering temperatures are all below 1800℃. Preset sintering parameters refer to a set of process settings used to control the solid-state reaction rate, diffusion kinetics, and valence state transformation conditions. These parameters include at least the temperature range, holding time, and gas composition ratio in the reaction atmosphere for each stage. The reaction atmosphere can be nitrogen or a mixture of nitrogen and hydrogen; the gas ratio affects the nitrogen partial pressure and reducing power of the system. Staged sintering refers to dividing the sintering process into multiple stages with different temperatures and atmospheric effects. This scheme includes at least a first stage and a second stage, with the first stage temperature higher than the second stage. Both stages are below 1800℃ to reduce dependence on ultra-high temperature process conditions.

[0030] The purpose of this step is to separate and synergistically address the two process objectives of main crystal formation and effective activation of luminescent centers. The first sintering stage focuses on promoting solid-state reactions of raw materials such as Si3N4, AlN, and Al2O3 to form a β-Sialon main crystal framework, while simultaneously completing component substitution and phase structure stabilization. The second sintering stage focuses on promoting the valence state transformation of Eu and optimizing the local coordination environment under lower temperatures and more suitable atmospheres, thereby increasing the number and effectiveness of luminescent centers.

[0031] The first sintering stage involves heating to a preset high-temperature range and then holding it at that temperature to allow for sufficient reaction and diffusion at the raw material interface. If necessary, an inert or weakly reducing atmosphere can be used to suppress the formation of oxygen-related impurities and ensure a stable nitriding environment. The second sintering stage can be achieved after the first stage by adjusting to a lower temperature range and maintaining it for a certain period of time. By controlling the reducing properties of the reaction atmosphere and the nitriding conditions, the conversion of Eu3+ to Eu2+ can be promoted and its occupancy environment in the crystal lattice can be stabilized.

[0032] Preferably, the phased switching can be accomplished by continuous cooling or stepped cooling, and different chemical driving forces can be achieved in each phase by setting the gas ratio.

[0033] S3. Perform rapid cooling treatment on the sintered material according to the preset cooling rate and preset cooling time to obtain a phosphor sample; The preset cooling rate refers to the required rate of temperature reduction after sintering, such as a cooling rate of several degrees Celsius per minute. The preset cooling time refers to the maximum allowable time for the temperature to drop from the sintering end temperature to the safe or target temperature range. Rapid cooling refers to completing the temperature drop in a short time to suppress phase separation, secondary reactions, or valence state reversals that may occur during the high-temperature stage.

[0034] The purpose of this step is to solidify the phase structure and luminescent center state formed in the second sintering stage, avoiding performance drift caused by component redistribution, continued grain growth, or changes in the local redox environment during slow cooling. For the β-Sialon:Eu system, the diffusion ability is strong in the high-temperature range. If the cooling is too slow, local phase equilibrium adjustments, trace impurity phase precipitation, or changes in the effective coordination environment of Eu may occur, ultimately manifesting as broadened full width at half maximum (FWHM), peak shift, or decreased external quantum efficiency. Therefore, by presetting the cooling rate and cooling time constraints, the post-sintering state is rapidly frozen, improving the repeatability of the results.

[0035] Specifically, this can be achieved through rapid in-furnace cooling strategies, such as increasing the flow rate of inert cooling gas to enhance convective heat transfer, or employing a controllable rapid cooling curve to allow the furnace temperature to cross the temperature range prone to phase transitions or phase separations within a limited time. The heat dissipation path can also be optimized by combining the furnace structure and crucible loading method to reduce localized re-reactions caused by internal temperature gradients within the sample. The beneficial effect of this step is to suppress secondary evolution of the sintered material during cooling, maintain the stability of the main crystal structure and the Eu2+ activation state, reduce batch-to-batch differences in luminescence performance introduced by different cooling conditions, and provide a more comparable sample basis for subsequent performance testing.

[0036] S4. Perform performance tests on the phosphor sample to obtain test results, wherein the test results include Eu site distribution, valence ratio and luminescence performance parameters; Specifically, Eu occupancy distribution refers to the structural position and spatial distribution characteristics of Eu in the β-Sialon lattice. Evidence can be obtained indirectly or directly through structural characterization methods, such as obtaining lattice parameter variations and potential occupancy information through diffraction refinement, or obtaining local coordination environments and bond length variations through absorption spectroscopy structural analysis, thereby inferring the occupancy and uniformity of Eu distribution. Valence state ratio refers to Eu... 2+ With Eu 3+ The relative content of valence states can be obtained through methods such as X-ray photoelectron spectroscopy to obtain the distribution information of valence state-related peaks and to assess the proportion of valence states. Luminescence performance parameters refer to the optical performance indicators of phosphors, such as emission peak positions, full width at half maximum (FWHM), and external quantum efficiency.

[0037] This step converts the structure and performance state of the phosphor sample into a quantifiable feedback statement, which facilitates the adjustment of subsequent sintering parameters and avoids the root cause of structural defects and abnormal valence states that are easily overlooked by relying solely on experience or a single luminescence index, leading to incorrect parameter tuning direction or low efficiency. Structural characterization can be achieved using X-ray diffraction combined with fine-tuning to obtain lattice and phase purity information. If necessary, local structural probing can be used to obtain coordination environment parameters and distribution consistency indices around Eu. Valence state characterization can be performed using XPS to obtain Eu... 2+ With Eu 3+ The valence state characteristics are determined and their proportions are evaluated. Luminescence characterization can be achieved by obtaining peak positions and full width at half maximum (FWHM) through photoluminescence spectroscopy, and external quantum efficiency can be obtained through quantum efficiency testing.

[0038] S5. Adjust the preset sintering parameters according to the deviation between the test results and the target parameter window; Specifically, the target parameter window refers to the allowable range set for site distribution, valence state ratio, and luminescence performance parameters. For example, it limits the external quantum efficiency to no less than a certain threshold, the full width at half maximum (FWHM) to no more than a certain threshold, and the Eu... 2+ The proportion is within a certain range and the structural characterization meets the phase purity or lattice parameter range, etc.

[0039] This step establishes a process convergence mechanism constrained by a target parameter window, transforming multi-step sintering from a one-time, fixed-parameter production method into an iteratively optimized preparation process. The formation and activation of β-Sialon:Eu luminescent centers are influenced by multiple factors, including raw material conditions, loading, and furnace variations, all of which cause fluctuations in results. By adjusting sintering parameters based on these deviations, unavoidable disturbances can be incorporated into a manageable parameter tuning framework, gradually bringing the results closer to the target window, rather than relying on one-time empirical parameters.

[0040] Specifically, a phased parameter update approach can be adopted. For example, the temperature and holding time can be adjusted to meet the requirements of main crystal formation in the first sintering stage, and the atmosphere ratio and heat treatment conditions can be adjusted to meet the requirements of valence state transformation in the second sintering stage, while maintaining the upper limit of the sintering temperature below 1800℃. A range for parameter adjustment can also be established by combining historical batch data to avoid oscillations caused by over-adjustment. The beneficial effect of this step is that it establishes a correspondence between parameter adjustments and measurable structure, valence state, and luminescence indicators, improving the interpretability and repeatability of parameter tuning, reducing time and material consumption caused by blind trial and error, and providing a data foundation for the subsequent establishment of a stable process window.

[0041] S6. Based on the adjusted preset sintering parameters, return to the step of controlling the reactor to perform staged sintering under the reaction atmosphere to obtain sintered materials according to the preset sintering parameters, until the test results of the phosphor sample meet the target parameter window.

[0042] Specifically, after adjustments, the entire method is constructed as a closed-loop iterative process, enabling the preparation method to not only complete a single synthesis but also gradually approach the target performance through multiple iterations. Returning to the sintering step means re-performing the staged sintering with updated parameters and repeatedly obtaining samples and test results. Multiple comparisons reduce deviations until the test results fall within the target parameter window. This iterative mechanism enables the method to cope with uncertainties such as batch variations in raw materials and changes in equipment status, thereby improving stability and consistency during large-scale production.

[0043] Preferably, the step of controlling the reactor to perform staged sintering to obtain sintered materials under a reaction atmosphere and according to preset sintering parameters includes... S21. According to the first sintering parameters, the mixture is sintered at high temperature under the first reaction atmosphere to form the main crystal of the narrow-band green phosphor and obtain the initial sintered material. The first sintering parameters include a first sintering temperature and a first holding time. The first sintering temperature is between 1630 and 1750°C, the first holding time is between 1 and 4 hours, and the first reaction atmosphere is nitrogen or a mixed gas including nitrogen and hydrogen. Specifically, in this step, the mixture obtained in step S1 is first subjected to a first-stage high-temperature sintering according to the first sintering parameters. This allows the silicon nitride, aluminum nitride, aluminum oxide, and europium dopant source to undergo solid-state reactions and phase rearrangement under high-temperature conditions, gradually forming the main crystalline framework of β-Sialon:Eu. The first sintering temperature is limited to between 1630 and 1750°C, and the first holding time is limited to between 1 and 4 hours. This ensures sufficient diffusion and reaction processes between the reactants, reducing the probability of unreacted residual phases or impurity phases forming, thereby providing a stable lattice support for subsequent valence state control.

[0044] At the same time, the gas composition in the reactor is set according to the first reaction atmosphere. The first reaction atmosphere is nitrogen or a mixed gas containing nitrogen and hydrogen, so that the sintering environment maintains the stability of the matrix structure formation under the nitriding-guided conditions.

[0045] Using nitrogen or a mixed gas with low hydrogen content is beneficial for prioritizing the construction of the matrix phase and grain growth during the main crystal formation stage, reducing the uncertainties caused by an overly strong reducing environment on the reaction path before the main crystal has fully formed. Through the above-mentioned high-temperature sintering and atmosphere control, an initial sintered material is obtained, which is mainly composed of β-Sialon main crystals and provides the reaction basis for the second stage of low-temperature reduction sintering.

[0046] S22. According to the second sintering parameters, the initial sintering material is subjected to low-temperature reduction sintering under the second reaction atmosphere to promote Eu in the crystal lattice. 3+ To Eu 2+ The valence state transformation is used to obtain sintered material. The second sintering parameters include a second sintering temperature and a second holding time. The second sintering temperature is lower than the first sintering temperature. The second reaction atmosphere is a mixture of nitrogen and hydrogen. The hydrogen content of the second reaction atmosphere is higher than the hydrogen content of the first reaction stage. The pressures of the first and second reaction atmospheres are between 0.3 and 0.8 MPa.

[0047] Specifically, in this step, the furnace temperature is lowered from the first sintering temperature to the second sintering temperature according to the second sintering parameters and held at that temperature. This allows the initial sintered material to continue undergoing ion diffusion and local structural adjustment within a lower temperature range, promoting the valence transformation of trivalent Eu ions in the crystal lattice to divalent Eu ions. Setting the second sintering temperature lower than the first sintering temperature allows the valence transformation process to occur under a relatively mild thermal history, reducing the risk of phase re-decomposition, abnormal grain growth, or compositional segregation that may occur under high-temperature, long-term conditions. This allows valence state regulation to focus more on the already formed main crystal framework.

[0048] Simultaneously, the second reaction atmosphere employs a mixture of nitrogen and hydrogen, with a higher hydrogen content than that in the first reaction stage. This provides stronger reduction-directing conditions in the second stage, driving the conversion of trivalent Eu ions to divalent Eu ions from the atmosphere side and increasing the effective proportion of divalent Eu ions. The nitrogen component maintains a stable environment for the nitriding system, while the hydrogen component provides reducing power and participates in the atmosphere driving force for valence state regulation. Through low-temperature reduction sintering in the second stage, sintered materials are obtained, which, while maintaining the main crystal structure, further converge towards the target valence state ratio and luminescence performance.

[0049] It is important to note that in this step, the pressures of both the first and second reaction atmospheres are controlled between 0.3 and 0.8 MPa, ensuring that both sintering stages are carried out under slightly positive pressure conditions. This slightly positive pressure environment helps improve the stability of the nitriding system during sintering, suppresses adverse factors introduced by backflow of external gases, and provides consistent pressure boundary conditions for high-temperature main crystal formation and low-temperature valence state control, thereby improving the consistency and controllability of process execution across different batches.

[0050] Preferably, the second sintering temperature is between 1350-1380℃, the second preset holding time is 20-30 minutes, and the pressure of the first reaction atmosphere and the second reaction atmosphere is 0.4~0.6MPa.

[0051] Preferably, the initial sintering material is subjected to low-temperature reduction sintering in a second reaction atmosphere according to the second sintering parameters to promote Eu in the crystal lattice. 3+ To Eu 2+ After the valence state transformation to obtain the sintered material, the method further includes: S23. At the end of the second sintering stage, determine the annealing start temperature based on the real-time temperature and pressure inside the furnace. The purpose of this step is to set a starting point for the annealing process that matches the actual operating conditions, ensuring that annealing is not simply performed at a fixed temperature, but rather that it is continuously connected to the thermal state at the end of the second sintering stage. After the second sintering stage, the furnace temperature and pressure may fluctuate due to variations in charge quantity, atmosphere flow rate, and thermal inertia. Directly starting annealing at a fixed temperature can easily lead to inconsistencies in the annealing starting points of different batches, resulting in drift in the microstructure and luminescent properties of the final material. By reading the real-time temperature and furnace pressure and determining the annealing starting temperature, the thermal history of the annealing stage is essentially aligned with the preceding reduction sintering stage. This reduces stress accumulation and phase fluctuations caused by abrupt temperature changes, making the subsequent annealing process more stable in regulating lattice defects and local stresses.

[0052] S24. Under an inert atmosphere or the second reaction atmosphere, the temperature of the reactor is reduced from the annealing start temperature to the preset annealing temperature at a first preset cooling rate, wherein the preset annealing temperature is between 900-1200°C. The purpose of this step is to establish a controllable annealing cooling path and maintain the stability of the divalent Eu ion-related states through atmosphere boundaries. The annealing temperature range is set between 900-1200℃, typically within a temperature range where the main crystal structure is stable but the lattice still possesses a certain atomic / ion migration capability. This temperature range is beneficial for heat-treating and reducing local defects, stresses, and microscopic inhomogeneities formed during the second sintering stage, while preventing a return to the high-temperature region that could trigger unnecessary phase rearrangement. A first preset cooling rate is used to lower the temperature to the annealing temperature, ensuring a repeatable thermal history for the annealing process. This avoids excessively rapid cooling that could cause residual stress freezing, and also avoids excessively slow cooling that could lead to continued local component segregation. Regarding the atmosphere, choosing either an inert atmosphere or a second reaction atmosphere is equivalent to providing two types of selectable boundary conditions for annealing. An inert atmosphere is used to reduce additional reaction interference, making the annealing primarily a heat treatment effect. A second reaction atmosphere is used to maintain the reduction-oriented environment, ensuring the divalent Eu ion ratio and local coordination environment remain stable during annealing, preventing undesirable valence state reversion. By limiting the atmosphere and cooling rate together, the influence of the annealing stage on the structure and valence state can be made more controllable.

[0053] S25. Hold the material at the preset annealing temperature for a third preset time to obtain the final sintered material, wherein the third preset time is between 10 and 20 minutes.

[0054] The purpose of this step is to allow the material sufficient heat treatment time in the annealing temperature range to complete defect relaxation, stress release, and local structural homogenization, thereby improving the stability and luminescence consistency of the final sintered material. The third preset time is limited to between 10-20 minutes, ensuring that the annealing is effective while avoiding the side effects of excessively long holding times that could lead to continued grain growth or local phase evolution. After the holding time, the final sintered material is obtained. Its significance lies in further stabilizing the main crystal structure and the related states of divalent Eu ions formed in the previous multi-step sintering process, making it easier for the final product to achieve more consistent performance in luminescence indicators such as emission peak position, full width at half maximum (FWHM), and quantum efficiency.

[0055] Preferably, the performance testing of the phosphor sample to obtain test results includes: S41. Perform extended X-ray absorption fine structure (EXAFS) testing on the phosphor sample to obtain structural characterization information, wherein the structural characterization information includes coordination environment parameters and site distribution parameters of Eu ions in the β-Sialon lattice. This step is used to obtain local structural information of divalent or trivalent Eu ions in the β-Sialon lattice to support the determination of site distribution and coordination environment. The luminescence properties of β-Sialon:Eu are closely related to the lattice position of the Eu ion and the surrounding atomic configuration. Macroscopic phase analysis alone is often insufficient to reflect the true state of the Eu ion at the local scale. EXAFS testing, by measuring the fine structural changes near the absorption edge of the target element, can reflect the local coordination characteristics such as the type, number, and distance of neighboring atoms around the element, thus forming coordination environment parameters. The coordination environment parameters are used to characterize whether the types and geometric relationships of coordinating atoms around the Eu ion are close to the target lattice environment, while the site distribution parameters are used to characterize the degree of difference in the distribution of Eu ions at different lattice positions or in different local environments.

[0056] This structural characterization information can link the formation of the main crystal in the first sintering stage with the microstructure state after the valence state transformation in the second sintering stage, providing a basis for subsequent identification of structural deviations and offering more targeted references for adjusting sintering temperature, holding time, or atmosphere ratio.

[0057] S42. X-ray photoelectron spectroscopy (XPS) was performed on the phosphor sample to obtain valence state characterization information, specifically Eu. 2+ With Eu 3+ The proportion of price states; This step is used to obtain the valence ratio of divalent Eu ions to trivalent Eu ions in the sample to evaluate the contribution of the second sintering stage and subsequent processes to the valence conversion effect. The green luminescent center of β-Sialon:Eu is mainly related to divalent Eu ions. A high proportion of trivalent Eu ions often indicates insufficient reduction or incomplete valence conversion, which may lead to substandard luminescence efficiency or batch-to-batch fluctuations. XPS testing, by measuring the binding energy and peak shape characteristics of the element's core energy level, can distinguish the energy level differences of the same element in different valence states, thereby obtaining valence characterization information and determining the valence ratio of divalent Eu ions to trivalent Eu ions.

[0058] The valence ratio is an important component of subsequent deviation determination. If the target parameter window requires the proportion of divalent Eu ions to reach a certain level, the XPS results can directly indicate whether the second reaction atmosphere, the second sintering temperature, and the holding time need to be adjusted, making it easier to translate process optimization into quantifiable indicators.

[0059] S43. Perform luminescence performance testing on the phosphor sample to obtain luminescence performance parameters, wherein the luminescence performance parameters include at least one of emission peak position, full width at half maximum (FWHM), and external quantum efficiency.

[0060] This step evaluates the final applicable performance and translates the characterization results of structure and valence states into actual luminescence performance. Luminescence performance parameters include at least one of the following: emission peak position, full width at half maximum (FWHM), and external quantum efficiency (ESE). The emission peak position characterizes the emission color and its matching degree with the target green band; the FWHM characterizes whether the narrow-band luminescence characteristics meet the requirements of high color gamut applications; and the EES characterizes the conversion efficiency from excitation light to emission light and the overall luminescence intensity level. Luminescence performance testing comprehensively reflects the combined effects of crystal structure, Eu ion occupancy, and valence state ratio, thus serving as a direct basis for setting target parameter windows and determining whether standards are met.

[0061] By combining the luminescence performance parameters of S43 with the structural characterization information of S41 and the valence state characterization information of S42, it is possible to distinguish whether the source of performance deviation is structural factors, valence state factors or a combination of both, thus providing a clearer direction for the subsequent adjustment of preset sintering parameters and reducing blind trial and error.

[0062] Preferably, adjusting the preset sintering parameters based on the deviation between the test results and the target parameter window includes: S51. Based on the difference between the test results and the target parameter window, obtain deviation information, wherein the deviation information includes the deviation direction and the corresponding deviation degree of the fixed structure deviation, valence state deviation and luminescence deviation; This step transforms the test results into deviation descriptions that can be used for process parameter tuning. The test results include structural characterization information, valence state characterization information, and luminescence performance parameters, while the target parameter window provides the target ranges for these indicators. By comparing the test results with the target parameter window, three types of deviation information can be obtained: structural deviation, valence state deviation, and luminescence deviation. The deviation direction indicates the direction of the test result's deviation from the target window, such as falling above or below the upper or lower limit of the target window, or being within the window but close to the boundary. The deviation degree describes the magnitude of the deviation, indicating whether it is slight or significant, thus providing a basis for subsequently determining the adjustment priority and intensity.

[0063] By breaking down deviations into structural deviations, valence state deviations, and luminescence deviations, performance issues at different levels can be distinguished. Structural deviations better reflect the state of host crystal formation and site distribution; valence state deviations better reflect whether the ratio of divalent to trivalent Eu ions meets the target; and luminescence deviations directly correspond to application indicators such as peak position, full width at half maximum (FWHM), and external quantum efficiency. This step establishes a unified input for subsequent correlation analysis and parameter locking, enabling the parameter tuning process to rely on structured information about the type and direction of deviation rather than empirical descriptions.

[0064] S52. Obtain the correlation data and cross-influence degree of the preset sintering parameters and the deviation information, wherein the preset sintering parameters include a first sintering parameter and a second sintering parameter, and the correlation data is used to characterize the relationship between the changes in the preset sintering parameters and the deviation information; This step establishes the correlation between parameter changes and deviation changes. The preset sintering parameters include a first sintering parameter and a second sintering parameter, actually covering parameters such as temperature, holding time, and reaction atmosphere gas ratio in both sintering stages. Correlation data characterizes the trend and magnitude of changes in a specific type of deviation (structural deviation, valence state deviation, or luminescence deviation) when a preset sintering parameter changes, thus reflecting the parameter's sensitivity to and direction of influence on this type of deviation. Through correlation data, it is possible to identify which parameters are more likely to reduce specific deviations and which parameter changes have little effect on those deviations.

[0065] The degree of cross-influence is used to characterize the coupling effect of parameter adjustment, that is, whether a change in a certain preset sintering parameter affects other deviations simultaneously, and whether the magnitude of the change is significant. Since the first sintering stage is more focused on main crystal formation, and the second sintering stage is more focused on valence state control and performance convergence, the effects of the first and second sintering parameters on the three types of deviations—structure, valence state, and luminescence—often exhibit cross-coupling. By introducing the degree of cross-influence, potential risks of entanglement can be identified before parameter adjustment, avoiding the significant amplification of other deviations in an effort to reduce one deviation, which could lead to difficulties in achieving overall convergence.

[0066] The technical significance of this step lies in providing a basis for subsequently determining the parameters to be adjusted and locking the parameters, thus transforming the parameter adjustment from a single-indicator-oriented process to a process optimization process that takes into account multiple index constraints, thereby improving iteration efficiency and batch stability.

[0067] S53. Based on the correlation data and the degree of cross-influence, determine the parameters to be adjusted and the locked parameters that will not be adjusted in the preset sintering parameters; This step involves selecting and constraining parameters from the adjustable parameter set, clarifying which parameters should be focused on in this round of adjustments and which should remain unchanged. Based on correlation data, parameters that have a more direct and sensitive impact on deviations can be prioritized, making the adjustments more targeted. Based on the degree of cross-influence, parameters that are likely to cause significant fluctuations in multiple types of deviations simultaneously can be identified and set as locked parameters, thereby reducing the coupling complexity of the adjustment process and avoiding situations where adjusting one parameter causes multiple indicators to drift simultaneously.

[0068] The determination of the parameters to be adjusted involves selecting the parameter that matches the current deviation direction from the first and second sintering parameters as the adjustment target, ensuring that its changes can drive the deviation towards the target parameter window. The determination of the locked parameters involves keeping these parameters unchanged within the current adjustment cycle, ensuring that the source of influence for this round of parameter tuning is relatively singular, facilitating the identification of causal relationships from test results and forming stable correlation data updates. By distinguishing between the parameters to be adjusted and the locked parameters, a phased and round-by-round parameter optimization path can be achieved, making the parameter tuning of the multi-step sintering process more controllable and reducing blind trial and error.

[0069] S54. Under the condition that the locking parameter remains unchanged, the parameter to be adjusted is adjusted according to the deviation information to obtain the updated preset sintering parameter.

[0070] This step performs the actual parameter updates and, under the constraint of locked parameters, concentrates the adjustment effect on a small number of parameters to be adjusted. Locking the parameters unchanged controls the variable dimensions of this round of adjustments, making subsequent sintering and testing results more sensitive and interpretable to parameter changes. Adjusting the parameters to be adjusted based on deviation information means that the adjustment direction and magnitude match the deviation direction and degree. The aim is to reduce the deviation of structural deviation, valence deviation, and luminescence deviation from the target parameter window, allowing the test results to gradually approach the target parameter window.

[0071] After adjustment, the updated preset sintering parameters are obtained, which will serve as the input parameters for the next round of staged sintering. Combining the correlation data and cross-influence degree formed in the previous steps, the updated preset sintering parameters can achieve directional convergence of performance deviations while maintaining process stability, providing process conditions closer to the target window for subsequent repeated sintering and testing.

[0072] Preferably, determining the parameters to be adjusted and the locked parameters not to be adjusted in the preset sintering parameters based on the correlation data and the degree of cross-influence includes: S531. Based on the deviations of the structural deviation, the valence state deviation, and the luminescence deviation relative to the target parameter window, determine the target deviation of the current adjustment cycle, and determine the priority control thermal process segment corresponding to the target deviation. The priority control thermal process segment includes at least one of the following: a first sintering stage, a second sintering stage, an annealing stage, and a rapid cooling stage. Specifically, structural deviations, valence state deviations, and luminescence deviations correspond to lattice occupancy and coordination environment, Eu, and other parameters, respectively. 2+ With Eu 3+The results include performance indicators such as the ratio, peak full width at half maximum (FWHM), and external quantum efficiency. After comparing the three types of deviations with the target parameter window one by one, the type with the most significant deviation or the greatest impact on the final narrowband luminescence is selected as the target deviation. This avoids simultaneously pursuing all three types of indicators in the same round, which could lead to mutual cancellation of tuning directions. Further determining the priority thermal process segment for tuning transforms the abstract rules of subsequent tuning into specific process controls for the first sintering stage, the second sintering stage, the annealing stage, or the rapid cooling stage. For example, valence state deviations tend to be corrected more readily in the second sintering stage and the annealing stage, while luminescence deviations, especially FWHM anomalies, are more suitable for prioritizing the rapid cooling stage, thereby improving the hit rate of tuning and reducing ineffective iterations.

[0073] In an optional implementation, determining the priority control thermal process segment includes establishing a correspondence between the target deviation and the sintering thermal process segment based on the type of the target deviation, so that the parameter adjustment action is preferentially applied to the sintering stage that is most sensitive to the target deviation.

[0074] In an optional implementation, S531 can be further refined into the following steps: S5311. Obtain the results of the previous round of testing and extract three types of deviation indicators; In this step, based on the test results of the previous round of phosphor samples, structural characterization indices for characterizing structural deviations, valence state characterization indices for characterizing valence state deviations, and luminescence characterization indices for characterizing luminescence deviations are extracted to form a deviation evaluation input set. The structural characterization indices can be characterized by site distribution or coordination environment parameters, and the valence state characterization indices can be characterized by Eu... 2+ With Eu 3+ Valence state ratio characterization, the emission characterization index can be characterized by emission peak position, full width at half maximum (FWHM), or external quantum efficiency.

[0075] S5312. Calculate the deviation direction of the three types of deviations relative to the target parameter window respectively; In this step, various deviation indicators are compared with the upper and lower limits of the target parameter window to determine whether the corresponding deviation indicator is in a higher or lower direction outside the target parameter window. This direction is then used as the basis for selecting the subsequent thermal history section and determining the parameter adjustment direction.

[0076] S5313. Calculate the degree of deviation for each of the three types of deviations and rank the deviations by intensity. In this step, for deviation indicators that are outside the target parameter window, the deviation magnitude between them and the target parameter window boundary is calculated to obtain the degree of structural deviation, the degree of valence deviation, and the degree of luminescence deviation. The deviation intensity is then sorted according to the magnitude of the three types of deviation to characterize the type of deviation that needs to be corrected first in the current adjustment cycle.

[0077] S5314. Determine the target deviation for the current adjustment cycle based on deviation intensity ranking. In this step, the deviation type with the largest degree of deviation is selected as the target deviation for the current adjustment cycle; when there are at least two types of deviation with the same degree of deviation or a difference less than the preset difference threshold, the deviation type that has a more direct impact on luminescence performance is determined as the target deviation, or the valence state deviation is determined as the target deviation to prioritize ensuring the stability of Eu valence state transition.

[0078] S5315. Determine the priority control thermal process segment based on the target deviation type; In this step, a priority thermal process segment is determined based on the type of target deviation. This priority thermal process segment includes at least one of the following: a first sintering stage, a second sintering stage, an annealing stage, and a rapid cooling stage. Specifically, when the target deviation is a structural deviation, the first sintering stage or the annealing stage is determined as the priority thermal process segment; when the target deviation is a valence state deviation, the second sintering stage or the annealing stage is determined as the priority thermal process segment; and when the target deviation is a luminescence deviation, the rapid cooling stage is determined as the priority thermal process segment.

[0079] S5316, Output the binding result of target deviation and priority control thermal history segment; In this step, the target deviation type, deviation direction, deviation degree, and corresponding priority control thermal history segment are output as inputs for subsequent candidate adjustment parameter screening and parameter adjustment processes, so that the parameter adjustment action can be limited to the priority control thermal history segment.

[0080] S532. Based on the correlation data, determine the response relationship of each preset sintering parameter to the target deviation, and determine the preset sintering parameter corresponding to the priority control thermal history segment as the candidate adjustment parameter, wherein the preset sintering parameter includes at least a first sintering parameter, a second sintering parameter, an annealing parameter and a cooling parameter; Specifically, this step limits the candidate adjustment parameters to a set of parameters that are highly correlated with the target deviation and belong to the priority control thermal history segment, forming an executable parameter tuning set. Correlation data is used to characterize the response relationship between changes in preset sintering parameters and changes in the target deviation. For example, the first sintering parameter more easily affects main crystal formation and structural occupancy; the second sintering parameter and hydrogen ratio more easily affect Eu valence state transformation; annealing parameters affect defect repair and valence state stability; and cooling parameters affect the freezing method of the high-temperature structure or valence state during the cooling process. By first determining the response relationship and then selecting the parameters corresponding to the priority control thermal history segment as candidate adjustment parameters, the search space can be narrowed from all parameters to a few key parameters, reducing disturbances to non-critical stages, making each round of experiments more focused, and making the sintering window more likely to converge.

[0081] S533. Based on the degree of cross-influence, determine the degree of coupling influence of the candidate adjustment parameter on at least one type of non-target deviation while improving the target deviation, and obtain the cross-influence characteristics corresponding to the candidate adjustment parameter; The degree of cross-influence reflects the coupling relationship between different parameters and different performance indicators. For example, to improve Eu... 2+ Increasing the hydrogen content proportionally or changing the reduction conditions may introduce structural defects, thus affecting the full width at half maximum (FWHM). Similarly, adjusting the first sintering temperature to improve the structure may alter the substrate state of subsequent reduction transformations, leading to valence state fluctuations. Quantifying this coupled effect as a cross-influence characteristic is equivalent to attaching an impact profile on non-target deviations to each candidate parameter before parameter tuning. This ensures that subsequent locking and selection no longer solely considers whether the target deviation is improved, but also takes into account overall performance stability.

[0082] S534. When the cross-influence feature of a candidate adjustment parameter indicates that its influence on at least two types of non-target deviations reaches a preset influence threshold, the candidate adjustment parameter is determined as a locked parameter and kept unchanged, so as to avoid introducing significant fluctuations in at least two types of non-target deviations during the adjustment of the target deviation. The purpose of this step is to establish a parameter locking mechanism to avoid introducing large fluctuations in multidimensional performance to correct a single bias, which would cause the sample to oscillate repeatedly across multiple indicators. Specifically, when the cross-influence characteristics of a candidate adjustment parameter show that it will cause changes in at least two types of non-target biases to reach a preset influence threshold, this parameter is identified as a locked parameter and kept unchanged. The technical implication here is that parameters with excessive influence on multiple indicators are considered highly coupled sources and are not prioritized for adjustment before the current target bias has stabilized and converged, thereby reducing the linkage interference between the structure, valence state, and luminescence indicators. The beneficial effects of this approach are reduced uncontrollable factors during iteration, avoiding situations where the target bias improves but the other two indicators deteriorate significantly, improving overall convergence efficiency, and enhancing the stability and repeatability after the final parameter window is reached.

[0083] S535. When multiple candidate adjustment parameters can improve the target deviation and their influence on the non-target deviation does not reach the preset influence threshold, the candidate adjustment parameter with a cross-influence degree lower than the preset cross-influence degree threshold is determined as the parameter to be adjusted, and the remaining candidate adjustment parameters are determined as locked parameters.

[0084] When all candidate adjustment parameters can improve the target deviation and the side effects are within acceptable limits, the parameter least likely to affect other indicators is selected as the parameter to be adjusted, while the remaining parameters remain locked to maintain process baseline stability. When multiple candidate parameters can improve the target deviation, adjusting them simultaneously often leads to a stronger superposition effect of thermal history, making it difficult to attribute the response relationship and determine which parameter is effective in the next round. By screening the candidate adjustment parameter with the least coupling through the cross-influence threshold, it is equivalent to prioritizing the adjustment channel with the least disturbance to the system, allowing each iteration to introduce only a single main variable, facilitating the establishment of a stable parameter response relationship, reducing the number of trial and error attempts, and making the final sintering parameter combination easier to reproduce in batches.

[0085] Preferably, the step of adjusting the parameter to be adjusted according to the deviation information to obtain the updated preset sintering parameters, under the condition that the locking parameter remains unchanged, includes: S541. Obtain the current parameter value and the corresponding allowable adjustment range of the parameter to be adjusted, and determine the adjustment direction of the parameter to be adjusted according to the deviation direction between the target deviation and the target parameter window; Specifically, the current parameter value to be adjusted corresponds to the actual set value used in the current sintering process. The allowable adjustment range corresponds to the adjustable interval jointly defined by the process equipment capability, the safety boundary of the material system, and existing experience windows. For example, the first sintering temperature, the second sintering temperature, the holding time, the hydrogen content in the atmosphere, the furnace pressure, and the cooling rate all have boundaries that can be adjusted upwards or downwards. The deviation direction is used to characterize whether the test result is too high or too low relative to the target parameter window. For example, the Eu2+ ratio is lower than the window, the half-width at half-maximum is higher than the window, and the emission peak position deviates from the window. By mapping the deviation direction to the parameter adjustment direction, subsequent parameter adjustments are driven by the results and have interpretability, reducing blind trial and error and improving the effectiveness of a single iteration.

[0086] S542. Determine the target control amplitude level of the priority control thermal history segment based on the degree of deviation of the target deviation; The degree of deviation can be understood as the magnitude of the distance or the strength of the deviation between the test result and the target parameter window. A larger deviation requires a stronger control amplitude to accelerate convergence; a smaller deviation allows for a more precise approximation of the window and maintains performance stability. Dividing the control amplitude into levels binds the parameter tuning strategy to different thermal history stages. For example, in the second sintering stage or annealing stage, the control amplitude level can be reflected in different adjustments to the second sintering temperature, second holding time, hydrogen content, or annealing holding time. In the rapid cooling stage, it is reflected in different adjustments to the slope of the target cooling curve or the target flow rate range of the cooling gas. Through this hierarchical control, parameter tuning can be upgraded from simple numerical changes to a controlled, ordered regulation of the thermal history stages, improving convergence speed and reproducibility.

[0087] S543. According to the target amplitude level, perform a parameter adjustment on the sintering process corresponding to the parameter to be adjusted within the priority control thermal history segment to obtain candidate parameter values, and obtain candidate preset sintering parameters under the condition that the locked parameters remain unchanged. Adjusting parameters according to the target amplitude level involves specifically implementing the control intensity determined by S542 into changes to the setpoints of the parameters to be adjusted. For example, this might involve raising or lowering the second sintering temperature by a corresponding level within the allowable range, fine-tuning the hydrogen content within the allowable range, or adjusting the cooling rate according to a corresponding level. Locking parameters to remain unchanged ensures that parameters not belonging to the priority control segment in the first sintering stage, another sintering stage, annealing section, or cooling section remain at the baseline, preventing simultaneous changes in multiple parameters that could lead to difficulties in attributing the response relationship. This results in candidate preset sintering parameters with clear points of modification, facilitating the establishment of a correspondence between subsequent performance test results and parameter adjustment actions.

[0088] S545. Perform sintering based on the candidate preset sintering parameters and perform performance testing on the obtained phosphor sample to obtain the corresponding candidate test results; Performing sintering involves applying candidate preset sintering parameters to the reactor at each stage of the control process, including temperature settings, holding time, reaction atmosphere ratio, furnace pressure, or cooling profiles for the corresponding thermal history segments. The resulting phosphor samples are then subjected to performance testing to output evaluation indicators directly corresponding to the target parameter window, such as Eu site distribution and Eu... 2+ With Eu 3+ Valence ratio, emission peak position, full width at half maximum (FWHM), and external quantum efficiency, etc. Since the target deviation type has been clearly defined in S531, the test results in this step can directly reflect the degree of improvement of the target deviation by this round of parameter tuning, and at the same time provide the changes in non-target deviations, providing a basis for whether to accept the candidate parameter in the future.

[0089] S546. Compare the difference between the candidate test results and the previous round of test results to determine whether the degree of deviation of the target deviation has decreased. Comparing the candidate test results with the previous round of test results essentially involves observing whether the target bias has decreased under the same evaluation dimensions, such as Eu. 2+ Whether the ratio approaches the window value, whether the half-width at half-maximum (HWHM) decreases and enters the allowable range, whether the emission peak position returns to the window range, or whether the site distribution is closer to the target coordination environment. By comparing these differences to determine whether the degree of deviation has decreased, we can avoid making static judgments based solely on a single test result. Instead, we can determine whether the parameter tuning direction is correct based on the iterative trend. The beneficial effect of this step is to improve the stability and robustness of closed-loop parameter tuning, enabling the system to gradually approach the target window in multiple iterations, rather than oscillating back and forth at the window edge.

[0090] S547. When the degree of deviation of the target deviation decreases, the candidate preset sintering parameters are determined as the updated preset sintering parameters. Confirming the candidate preset sintering parameters as the updated preset sintering parameters signifies that the adjustment of the priority control thermal history segment in this round has proven effective, and positive convergence has been achieved while keeping the parameters unchanged. This approach ensures the cumulative nature of the parameter tuning process; each effective adjustment is reflected in a new parameter state, allowing the target deviation to gradually enter and remain stably within the target parameter window. Its benefits include reducing the number of invalid experiments, shortening the iteration cycle to reach the target window, and making the final sintering parameter combination more reproducible.

[0091] S548. When the degree of deviation of the target deviation does not decrease or increases in the opposite direction, keep the locking parameter unchanged and revert the parameter to be adjusted to the parameter value of the previous round.

[0092] Maintaining the locked parameters ensures the stability of the overall process baseline, allowing the rollback action to be performed only on the primary variable—the parameter to be adjusted—ensuring the system returns to a controllable state. Rolling back the parameter to be adjusted to the previous value can be understood as canceling the parameter changes made during the priority control thermal history period, allowing the next round to select a more suitable adjustment range or use other candidate adjustment parameters for correction. The benefits of this step include preventing the deviation from increasing and causing significant fluctuations in sample performance, reducing experimental costs and time consumption, and improving the safety and convergence reliability of the closed-loop parameter tuning process.

[0093] Preferably, the step of rapidly cooling the sintered material according to a preset cooling rate and a preset cooling time to obtain a phosphor sample includes: S31. At the end of the second sintering stage, the end temperature and pressure inside the reactor are obtained to determine the initial cooling temperature of the sintered material. At the end of the second sintering stage, the temperature and pressure inside the furnace are direct indicators of the sintering completion state, and may fluctuate due to factors such as the charge amount, furnace thermal inertia, and atmosphere. Determining the initial cooling temperature based on the completion temperature and furnace pressure allows for a continuous connection between the cooling stage and the preceding sintering stage, avoiding inconsistencies in the cooling thermal history of different batches due to a fixed starting point. This reduces fluctuations in luminescence performance caused by subsequent phase and microstructure differences.

[0094] S32. Establish a target cooling curve based on the initial cooling temperature, preset cooling termination temperature, preset cooling rate and preset cooling time, and calculate the target flow rate range of the cooling gas, wherein the cooling gas is argon, the preset cooling rate is greater than or equal to 50℃ / min, and the cooling time is less than or equal to 30min. The initial cooling temperature and the preset cooling termination temperature define the cooling range, while the preset cooling rate and preset cooling time define the cooling intensity and duration. This establishes the target cooling curve, forming the temperature change path that the cooling process should follow over time. Further calculation of the target flow rate range for the cooling gas maps the target cooling curve to controllable gas flow conditions, matching the cooling capacity with the target cooling rate. Specifying argon as the cooling gas helps provide an inert environment during the cooling phase and avoids introducing additional reaction factors. Setting a cooling rate greater than or equal to 50℃ / min and a cooling time less than or equal to 30min gives the cooling a "rapid cooling" characteristic, facilitating the suppression of phase separation or continued reactions that may occur in the high-to-medium temperature range.

[0095] S33. Under the condition of maintaining the furnace in a preset slightly positive pressure inert atmosphere, the cooling gas is introduced into the reactor according to the target flow rate range, so that the temperature inside the furnace decreases along the target cooling curve. Maintaining the furnace under a preset slightly positive pressure inert atmosphere serves two purposes: firstly, it ensures the stability of the furnace atmosphere, reducing the uncertainties caused by backflow of external gases; secondly, it provides stable pressure conditions for argon cooling, making the gas convection heat transfer capacity more controllable. Introducing argon gas according to the target flow rate range causes the furnace temperature to decrease along the target cooling curve. This means that cooling is not achieved by arbitrarily increasing the flow rate, but rather by achieving "curve-based cooling" within the preset range, thus ensuring consistent cooling thermal histories across different batches. This step directly determines whether the cooling process can effectively achieve the rapid cooling target and provides a basis for subsequent real-time monitoring and correction.

[0096] S34. During the cooling process, the real-time temperature inside the reactor is obtained according to the preset sampling cycle; The sampling period setting determines the temporal resolution of temperature monitoring, enabling continuous acquisition of real-time temperature sequences during the cooling process. Because the cooling process is affected by furnace thermal inertia, gas flow fluctuations, and the heat capacity of the charge, the actual temperature change may not strictly conform to the target cooling curve. Therefore, real-time temperature acquisition is necessary to reflect the current cooling state and provide a data basis for further calculations of the actual cooling rate and corrected flow rate.

[0097] S35. Based on the real-time temperature, obtain the temperature change at adjacent sampling times to correct the cooling gas flow rate, so that the actual cooling rate is maintained within the allowable deviation range of the target cooling curve. By analyzing temperature changes at adjacent sampling times, the actual cooling rate can be characterized. This actual cooling rate is then compared to the allowable deviation range corresponding to the target cooling curve, forming a basis for flow rate correction. Correcting the cooling gas flow rate to maintain the actual cooling rate within the allowable deviation range avoids the thermal stress risk caused by excessively rapid cooling and also prevents insufficient phase separation suppression due to excessively slow cooling. This step substantially improves the repeatability of the rapid cooling process, making the stabilization effect of the cooling stage on microstructure and performance more reliable.

[0098] S36. When the temperature inside the furnace drops to the preset cooling termination temperature, stop the cooling gas supply to obtain the phosphor sample.

[0099] The preset cooling termination temperature defines the critical temperature range that rapid cooling needs to cover. When the furnace temperature drops to this termination temperature, the cooling gas supply stops, signifying the completion of the rapid cooling phase and the beginning of a relatively gradual temperature change. This termination condition ensures that the cooling processes of different batches end at the same temperature point, guaranteeing a consistent rapid cooling thermal history for the samples. The resulting phosphor samples more stably retain the structure and valence state formed during the second sintering stage, reducing the interference of cooling differences on luminescence performance testing and subsequent parameter adjustments.

[0100] Example 2 Based on the preparation method of Example 1, Example 2 of the present invention also provides an LED package, namely an LED package structure, the LED package structure including an LED light-emitting unit, the LED light-emitting unit including an excitation chip and a phosphor combination, the phosphor combination including at least a narrow-band green phosphor prepared by the method of Example 1, the LED package structure being used for long-distance lighting applications.

[0101] Specifically, the phosphor combination includes β-Sialon:Eu narrowband green oxynitride phosphor prepared by the method of Example 1 of this invention. This phosphor can efficiently emit narrowband green light under blue / ultraviolet excitation; and can be combined with phosphors of other wavelengths (such as red nitride phosphors and yellow YAG:Ce phosphors) to ultimately output white light with high color rendering and high stability.

[0102] The excitation chip is typically a blue light chip or a near-ultraviolet chip, serving as an energy excitation source. The high-energy photons emitted by the chip provide excitation energy for the phosphor.

[0103] Because the emission peak of β-Sialon:Eu phosphor is concentrated around 530 nm and its full width at half maximum (FWHM) is less than 55 nm, its green light output is pure and intense. When paired with blue LED chips and red phosphors, it can significantly improve the color rendering index of LED light sources while also increasing luminous efficiency.

[0104] Narrow-band green phosphors exhibit excellent thermal stability and resistance to light decay, maintaining stable luminescence even under high-power operating conditions. This is particularly crucial for long-distance lighting applications such as stadiums, airport runways, and highways, ensuring color consistency and brightness uniformity even under strong light irradiation.

[0105] Because phosphors can be prepared at relatively low temperatures and under slight positive pressure, compared to traditional high-temperature and high-pressure methods, the energy consumption and equipment costs are significantly reduced. This not only lowers the barrier to entry in phosphor production but also creates conditions for controlling the overall cost of lighting fixtures.

[0106] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0107] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0108] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0109] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0110] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0111] It should also be noted that the exemplary embodiments mentioned in this invention describe methods or systems based on a series of steps or apparatus. However, this invention is not limited to the order of the steps described above; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0112] The above description is merely a specific embodiment of the present invention. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A method for preparing narrowband green phosphor by multi-step sintering and LED packaging, wherein the narrowband green phosphor is β-Sialon:Eu, characterized in that, The method includes: The raw materials are uniformly mixed according to a preset ratio to obtain a mixture, wherein the raw materials include silicon nitride, aluminum nitride, aluminum oxide and europium doping source; According to preset sintering parameters, the reactor is controlled to perform staged sintering under a reaction atmosphere to obtain sintered material. The preset sintering parameters include sintering temperature, holding time and gas ratio of the reaction atmosphere. The staged sintering includes at least a first sintering stage and a second sintering stage. The sintering temperature of the first sintering stage is higher than that of the second sintering stage. The sintering temperatures are all below 1800℃. The sintered material is rapidly cooled according to a preset cooling rate and a preset cooling time to obtain a phosphor sample. The phosphor sample was subjected to performance testing to obtain test results, wherein the test results include Eu site distribution, valence state ratio and luminescence performance parameters; Based on the deviation between the test results and the target parameter window, the preset sintering parameters are adjusted; Based on the adjusted preset sintering parameters, return to the step of controlling the reactor to perform staged sintering under the reaction atmosphere to obtain sintered materials, until the test results of the phosphor sample meet the target parameter window.

2. The method according to claim 1, characterized in that, The process involves controlling the reactor to perform staged sintering under a reactive atmosphere, according to preset sintering parameters, to obtain sintered materials, including... According to the first sintering parameters, the mixture is sintered at high temperature under the first reaction atmosphere to form the main crystal of the narrow-band green phosphor and obtain the initial sintered material. The first sintering parameters include a first sintering temperature and a first holding time. The first sintering temperature is between 1630 and 1750°C, the first holding time is between 1 and 4 hours, and the first reaction atmosphere is nitrogen or a mixed gas including nitrogen and hydrogen. According to the second sintering parameters, the initial sintering material is subjected to low-temperature reduction sintering under the second reaction atmosphere to promote Eu in the crystal lattice. 3+ To Eu 2+ The valence state transformation is used to obtain the final sintered material. The second sintering parameters include a second sintering temperature and a second holding time. The second sintering temperature is lower than the first sintering temperature. The second reaction atmosphere is a mixture of nitrogen and hydrogen. The hydrogen content of the second reaction atmosphere is higher than the hydrogen content of the first reaction stage. The pressures of the first and second reaction atmospheres are between 0.3 and 0.8 MPa.

3. The method according to claim 2, characterized in that, The second sintering temperature is between 1350-1380℃, the second preset holding time is 20-30 minutes, and the pressure of the first reaction atmosphere and the second reaction atmosphere is 0.4-0.6MPa.

4. The method according to claim 3, characterized in that, According to the second sintering parameters, the initial sintering material is subjected to low-temperature reduction sintering in a second reaction atmosphere to promote Eu in the crystal lattice. 3+ To Eu 2+ After the valence state transformation is completed to obtain the final sintered material, the method further includes: At the end of the second sintering stage, the annealing start temperature is determined based on the real-time temperature and pressure inside the reactor. Under an inert atmosphere or the second reaction atmosphere, the temperature of the reactor is reduced from the annealing start temperature to the preset annealing temperature at a first preset cooling rate, wherein the preset annealing temperature is between 900-1200°C. The material is held at the preset annealing temperature for a third preset time to obtain the final sintered material, wherein the third preset time is between 10 and 20 minutes.

5. The method according to any one of claims 1-4, characterized in that, The performance test of the phosphor sample, to obtain the test results, includes: The phosphor sample was subjected to extended X-ray absorption fine structure (EXAFS) testing to obtain structural characterization information, which included the coordination environment parameters and site distribution parameters of Eu ions in the β-Sialon lattice. X-ray photoelectron spectroscopy (XPS) was performed on the phosphor sample to obtain valence state characterization information, and Eu was obtained. 2+ With Eu 3+ The proportion of price states; The phosphor sample is subjected to luminescence performance testing to obtain luminescence performance parameters, wherein the luminescence performance parameters include at least one of emission peak position, full width at half maximum (FWHM), and external quantum efficiency.

6. The method according to claim 5, characterized in that, The step of adjusting the preset sintering parameters based on the deviation between the test results and the target parameter window includes: Based on the difference between the test results and the target parameter window, deviation information is obtained, wherein the deviation information includes the deviation direction and the corresponding deviation degree of the fixed structure deviation, valence state deviation and luminescence deviation; The correlation data and cross-influence degree of the preset sintering parameters and the deviation information are obtained, wherein the preset sintering parameters include a first sintering parameter and a second sintering parameter, and the correlation data is used to characterize the relationship between the changes of the preset sintering parameters and the deviation information; Based on the correlation data and the degree of cross-influence, determine the parameters to be adjusted and the locked parameters that will not be adjusted in the preset sintering parameters; Under the condition that the locking parameter remains unchanged, the parameter to be adjusted is adjusted according to the deviation information to obtain the updated preset sintering parameter.

7. The method according to claim 6, characterized in that, The step of determining the parameters to be adjusted and the locked parameters not to be adjusted in the preset sintering parameters based on the correlation data and the degree of cross-influence includes: Based on the deviations of the structural deviation, the valence state deviation, and the luminescence deviation relative to the target parameter window, the target deviation of the current adjustment cycle is determined, and the priority control thermal process segment corresponding to the target deviation is determined. The priority control thermal process segment includes at least one of the following: a first sintering stage, a second sintering stage, an annealing stage, and a rapid cooling stage. Based on the correlation data, the response relationship of each preset sintering parameter to the target deviation is determined, and the preset sintering parameter corresponding to the priority control thermal history segment is determined as the candidate adjustment parameter. The preset sintering parameter includes at least a first sintering parameter, a second sintering parameter, an annealing parameter, and a cooling parameter. Based on the degree of cross-influence, the degree of coupling influence of the candidate adjustment parameter on at least one type of non-target deviation while improving the target deviation is determined, and the cross-influence characteristics corresponding to the candidate adjustment parameter are obtained. When the cross-influence feature corresponding to a candidate adjustment parameter indicates that its influence on at least two types of non-target deviations reaches a preset influence threshold, the candidate adjustment parameter is determined as a locked parameter and remains unchanged, so as to avoid introducing significant fluctuations in at least two types of non-target deviations during the adjustment of the target deviation. When multiple candidate adjustment parameters can improve the target deviation and their influence on non-target deviations does not reach the preset influence threshold, the candidate adjustment parameter with a cross-influence degree lower than the preset cross-influence degree threshold is determined as the parameter to be adjusted, and the remaining candidate adjustment parameters are determined as locked parameters.

8. The method according to claim 7, characterized in that, The step of adjusting the parameter to be adjusted according to the deviation information under the condition that the locking parameter remains unchanged, to obtain the updated preset sintering parameter, includes: Obtain the current parameter value and the corresponding allowable adjustment range of the parameter to be adjusted, and determine the adjustment direction of the parameter to be adjusted based on the deviation direction between the target deviation and the target parameter window; Based on the degree of deviation of the target deviation, the target control amplitude level of the priority control thermal history segment is determined; According to the target amplitude level, the sintering process corresponding to the parameter to be adjusted is adjusted once within the priority control thermal history segment, and candidate preset sintering parameters are obtained under the condition that the locked parameters remain unchanged. Sintering is performed based on the candidate preset sintering parameters, and the performance of the resulting phosphor sample is tested to obtain the corresponding candidate test results. Compare the candidate test results with the previous round of test results to determine whether the degree of deviation of the target deviation has decreased; When the degree of deviation of the target deviation decreases, the candidate preset sintering parameters are determined as the updated preset sintering parameters; When the degree of deviation of the target deviation does not decrease or increases in the opposite direction, keep the locking parameter unchanged, switch the control amplitude level of the priority control thermal history segment to a smaller amplitude level and generate candidate parameter values ​​again, or roll back the parameter to be adjusted to the parameter value of the previous round.

9. The method according to any one of claims 1-4, characterized in that, The rapid cooling process of the sintered material according to a preset cooling rate and a preset cooling time to obtain a phosphor sample includes: At the end of the second sintering stage, the final temperature and pressure inside the reactor are obtained to determine the initial cooling temperature of the sintered material. A target cooling curve is established based on the initial cooling temperature, the preset cooling termination temperature, the preset cooling rate, and the preset cooling time, and the target flow rate range of the cooling gas is calculated. The cooling gas is argon, the preset cooling rate is greater than or equal to 50°C / min, and the cooling time is less than or equal to 30min. While maintaining the furnace in a preset slightly positive pressure inert atmosphere, the cooling gas is introduced into the reactor according to the target flow rate range, so that the furnace temperature decreases along the target cooling curve. During the cooling process, the real-time temperature inside the reactor is obtained according to a preset sampling period; The cooling gas flow rate is corrected by obtaining the temperature change at adjacent sampling times based on the real-time temperature, so that the actual cooling rate is maintained within the allowable deviation range of the target cooling curve. When the temperature inside the furnace drops to the preset cooling termination temperature, the cooling gas is stopped, and the phosphor sample is obtained.

10. An LED package, characterized in that, The LED package includes an LED light-emitting unit comprising an excitation chip and a phosphor assembly, wherein the phosphor assembly comprises at least a narrow-band green phosphor prepared by any one of claims 1-9, and the LED package is used for long-distance lighting applications.

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