Preparation method of europium-doped germanate red luminescent material

Abstract

The application discloses a preparation method of a europium-doped germanate red luminescent material, and is used for preparing a material with a chemical general formula of (0.025<=<=0.1). The method comprises the following steps: sodium carbonate, calcium carbonate, germanium dioxide and europium sesquioxide are weighed according to a metering ratio, wet grinding is carried out in a garnet mortar with anhydrous ethanol as a medium for 1-2 hours, and natural air drying is carried out; the dried powder is loaded into a corundum crucible and placed in a tube furnace, a solid phase reaction is carried out under an air atmosphere, the temperature is raised to 850 DEG C at a speed of 5 DEG C / min, and the temperature is kept for 6-8 hours; after the calcination is completed, the heating power is turned off, the product is naturally cooled to room temperature along with the furnace, and crushing and grinding are carried out to obtain the material. Through optimization of wet grinding and temperature control calcination and cooling parameters, the material powder agglomeration is avoided, and technical problems such as easy appearance of derived impurities in the synthesized product, low crystallinity and existence of residual stress in the crystal are solved.

Description

Technical Field

[0001] This invention relates to the field of inorganic luminescent material preparation technology, specifically a method for preparing europium-doped germanate red luminescent material. Background Technology

[0002] The synthesis process of inorganic luminescent materials directly affects their crystal structure and luminescence properties. High-temperature solid-state reaction is currently the main technical approach for preparing rare-earth-doped inorganic luminescent materials due to its mature operational procedures.

[0003] In conventional high-temperature solid-state synthesis processes, various inorganic precursor raw materials containing matrix elements and luminescent center elements are typically physically mixed in stoichiometric ratios. The mixed raw materials are then placed in a heating device for calcination, causing the raw material particles to diffuse and undergo solid-state reactions at high temperatures to form the target crystalline phase. After cooling, the luminescent material powder is obtained.

[0004] Existing methods for preparing luminescent materials have shortcomings in the raw material pretreatment stage. Conventional mixing methods are insufficient to overcome the agglomeration of precursor powder particles, resulting in uneven dispersion of the raw material components. Powder agglomeration reduces the contact interface for solid-phase reactions during subsequent calcination, leading to incomplete solid-phase reactions. Incomplete reactions result in impurity phase structures in the final synthesized luminescent material product, leading to reduced phase purity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing europium-doped germanate red luminescent materials, which solves the problems that existing germanate luminescent materials are prone to developing impurity phases, low crystallinity, and residual thermal stress within the crystal lattice due to improper control of process parameters during synthesis.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing europium-doped germanate red luminescent materials, used to prepare materials with the chemical formula […]. The red luminescent material, among which This indicates the mole fraction of europium ions doped and 0.025 ≤ ≤0.1, the preparation method includes the following steps: S1. Raw material processing: Weigh sodium carbonate, calcium carbonate, germanium dioxide and europium trioxide according to the stoichiometric ratio of the general chemical formula, mix them thoroughly and grind them to obtain a mixed powder; S2. High-temperature reaction: After drying the obtained mixed powder, it is placed in a high-temperature furnace and calcined in air atmosphere to cause solid-phase reaction of each raw material. S3. Post-processing: After calcination, the product is cooled to room temperature by furnace cooling and then ground to obtain the red luminescent material.

[0007] Preferably, in step S1, the stoichiometric ratio of sodium carbonate, calcium carbonate, germanium dioxide, and europium trioxide is as follows: .

[0008] Preferably, in step S1, the specific process of the grinding treatment is as follows: the fully mixed raw materials are transferred to an agate mortar and wet-ground using anhydrous ethanol as the dispersion medium for 1-2 hours.

[0009] Preferably, in step S2, the mixed powder is naturally air-dried under air conditions.

[0010] Preferably, in step S2, the naturally air-dried mixed powder is loaded into a corundum crucible, and the high-temperature furnace is a tube furnace.

[0011] Preferably, in step S2, the specific parameters of the calcination process are: heating from room temperature to 850°C at a heating rate of 5°C / min, and holding at 850°C for 6-8 hours.

[0012] Preferably, in step S3, after the product is cooled to room temperature, a sintered block is formed, and the sintered block is subjected to crushing and grinding treatment.

[0013] Preferably, in step S3, the furnace cooling method specifically involves turning off the heating power supply and allowing the product to cool naturally to room temperature inside the furnace.

[0014] This invention provides a method for preparing europium-doped germanate red luminescent materials. It has the following beneficial effects: 1. This invention involves weighing sodium carbonate, calcium carbonate, germanium dioxide, and europium trioxide according to the stoichiometric ratio of the chemical formula during the raw material processing stage, and then transferring the above raw materials to an agate mortar and performing wet grinding with anhydrous ethanol as the dispersion medium. This process prevents the precursor raw materials from agglomerating and ensures that they are uniformly dispersed, providing a sufficient solid-phase reaction interface for the subsequent high-temperature heat treatment process. This ensures that all components can undergo complete solid-phase reaction during the calcination stage, achieving the preparation effect of a pure phase composition of the luminescent material product without the derivation of impurity phases.

[0015] 2. This invention involves drying the mixed powder during the high-temperature reaction stage, placing it in an alumina crucible within a tube furnace, and heating it to 850°C at a heating rate of 5°C / min under an air atmosphere and holding it at that temperature for 6 to 8 hours. This allows the precursor powder to undergo a solid-phase transformation under these heat treatment parameters, forming a germanate matrix. This promotes the occupation of trivalent europium ions at specific sites in the matrix lattice, avoiding lattice distortion caused by excessively rapid heating and preventing incomplete reaction due to insufficient holding time. This results in the preparation of a luminescent material with a complete crystal phase structure and excellent microstructure.

[0016] 3. This invention employs a cooling method in the post-processing stage where the heating power is turned off, allowing the calcined product to cool naturally to room temperature within the high-temperature furnace. This releases the internal residual stress generated during the crystal growth stage, maintaining the physical integrity of the rigid crystal framework structure of the germanate matrix. It prevents microscopic cracking or an increase in internal defects caused by excessively rapid cooling, ensuring the stability of the crystal field environment of trivalent europium ions while maintaining the physical morphology, thus achieving a stable microcrystalline phase structure of the luminescent material. Attached Figure Description

[0017] Figure 1 Different in Embodiment 1 of the present invention X-ray diffraction (XRD) patterns of doped samples; Figure 2 This is a scanning electron microscope (SEM) image of the red luminescent material obtained in Example 2 of the present invention; Figure 3 This is a mapping diagram of the elemental distribution of the red luminescent material obtained in Example 3 of the present invention; Figure 4 This is the full X-ray photoelectron spectroscopy (XPS) spectrum of the red luminescent material obtained in Example 3 of the present invention; Figure 5 The photoluminescence spectrum of the red luminescent material obtained in Example 4 of this invention is a temperature-dependent photoluminescence spectrum. Figure 6 This is a quantum efficiency diagram of the red luminescent material obtained in Example 5 of the present invention; Figure 7 The XRD pattern of the red luminescent material obtained in Comparative Example 1; Figure 8 The following are excitation spectra of the red luminescent materials obtained in Examples 1-5 and Comparative Example 2 of this invention; Figure 9 The emission spectra of the red luminescent materials obtained in Examples 1-5 and Comparative Example 2 of this invention are shown. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The raw material amounts in the following examples are optimized actual amounts after taking into account the loss of sodium carbonate volatilization. They differ slightly from the theoretical stoichiometry but do not affect the phase composition and properties of the product.

[0020] Please see the appendix Figure 1-9 This invention provides a method for preparing europium-doped germanate red luminescent materials, used to prepare materials with the chemical formula […]. ( A red luminescent material. The preparation method includes the following steps: S1. Raw material processing: According to the chemical formula of the target product Sodium carbonate, calcium carbonate, germanium dioxide, and europium trioxide are weighed out according to their stoichiometric ratio, thoroughly mixed, and ground to obtain a mixed powder with a relatively uniform component distribution. Preferably, the grinding process is carried out in an agate mortar for 1-2 hours; the drying method is natural air drying.

[0021] S2. High-temperature reaction: After drying, the obtained mixed powder is placed in a high-temperature furnace and calcined in air to allow the raw materials to undergo a solid-phase reaction. Preferably, the calcination process is carried out in air at a heating rate of 5°C / min, from room temperature to 850°C and held at that temperature for 6-8 hours.

[0022] S3. Post-processing: After calcination, the product is cooled to room temperature by furnace cooling and then ground to obtain the target rare earth metal europium ion-doped germanate system red luminescent material.

[0023] The preparation process of the present invention will be further explained below with reference to specific embodiments and comparative examples.

[0024] Example 1

[0025] S1. Raw material proportioning and doping scheme design: Selection Doping mole fraction Four sets of comparison samples were set up with values ​​of 0.025, 0.033, 0.05, and 0.1, respectively.

[0026] The first group of samples consisted of: sodium carbonate 0.10g, calcium carbonate 0.10g, germanium oxide 0.21g, and europium trioxide 0.018g. The second group of samples consisted of: sodium carbonate 0.10g, calcium carbonate 0.10g, germanium oxide 0.21g, and europium trioxide 0.023g. The third group of samples contained: sodium carbonate 0.10g, calcium carbonate 0.10g, germanium oxide 0.21g, and europium trioxide 0.035g. The fourth group of samples contained: 0.10g sodium carbonate, 0.10g calcium carbonate, 0.21g germanium oxide, and 0.07g europium trioxide.

[0027] S2. Raw material mixing process: Place the weighed raw materials of each group into a clean container and mix them to ensure that the components are evenly dispersed on a macroscopic scale.

[0028] S3. Wet grinding treatment: Transfer the mixed raw materials to an agate mortar and perform wet grinding with anhydrous ethanol as the dispersion medium. The grinding time is controlled at 1-1.5h to obtain a precursor powder with a well mixed and relatively uniform particle size distribution.

[0029] S4. High-temperature solid-phase reaction synthesis: The ground powder is placed in an alumina crucible and placed in a tube furnace. The temperature is raised to 850°C at a heating rate of 5°C / min under air atmosphere, and held at this temperature for 6-8 hours to allow the raw materials to undergo a full solid-phase reaction.

[0030] S5. Powder Post-processing: After calcination, the samples were naturally cooled to room temperature in the furnace to obtain sintered blocks. The obtained blocks were crushed and ground to obtain europium ion-doped red luminescent materials for each group. S6. Structural Characterization Analysis: X-ray diffraction tests were performed on the four groups of samples (results are shown below). Figure 1 As shown in the figure, the positions and relative intensities of the diffraction peaks of each sample are basically consistent with the standard diffraction data of the target crystal phase. No obvious impurity phase peaks were observed, indicating that europium ions were successfully introduced into the crystal structure under this process condition.

[0031] Example 2

[0032] S1, Raw material ratio: Based on With a target composition of 0.025, europium trioxide 0.018g, sodium carbonate 0.10g, calcium carbonate 0.10g, and germanium oxide 0.21g were selected.

[0033] S2. Raw material mixing process: Place the raw materials in a clean container for mixing.

[0034] S3. Wet grinding treatment: Transfer to an agate mortar and wet grind with anhydrous ethanol as the dispersion medium for 1-1.5 hours.

[0035] S4. High-temperature solid-state reaction synthesis: The powder is placed in an alumina crucible and then placed in a tube furnace. The temperature is increased to 850℃ at 5℃ / min under air atmosphere and held for 6-8 hours.

[0036] S5. Powder post-processing: After the furnace is naturally cooled to room temperature, the resulting bulk material is pulverized and ground. Scanning electron microscope image of the product obtained by the above preparation method ( Figure 2 The data shows that the material consists of several irregular blocky grains with clear grain outlines, indicating that the obtained luminescent material has completed the crystallization process.

[0037] Example 3

[0038] S1, Raw material ratio: Based on With a target composition of 0.033, europium trioxide 0.023 g, sodium carbonate 0.10 g, calcium carbonate 0.10 g, and germanium oxide 0.21 g were selected.

[0039] The mixing, grinding, solid-phase reaction, and post-processing steps for S2 to S5 are the same as in Example 2. The prepared samples were characterized using elemental distribution and XPS analysis. Figure 3 , Figure 4 The constituent elements such as Ca, O, Na, and Ge are uniformly distributed, the XPS test characteristic peaks are clear, and the binding energy positions are consistent with the theoretical values, indicating that the preparation method of the present invention can obtain luminescent materials with correct elemental composition and high purity.

[0040] Example 4

[0041] S1, Raw material ratio: Based on With a target composition of 0.05, europium trioxide 0.035g, sodium carbonate 0.10g, calcium carbonate 0.10g, and germanium oxide 0.21g were selected.

[0042] The mixing, grinding, solid-state reaction, and post-processing steps for S2 to S5 are the same as in Example 2. Variable-temperature photoluminescence testing (…) Figure 5 This indicates that the emission peak position of the material obtained by this preparation method did not change significantly under varying temperature conditions, and the crystal structure remained stable.

[0043] Example 5

[0044] S1 Raw Material Ratio: Based on With a target composition of 0.1, europium trioxide 0.07g, sodium carbonate 0.10g, calcium carbonate 0.10g, and germanium oxide 0.21g were selected.

[0045] The mixing, grinding, solid-state reaction, and post-processing steps for S2 to S5 are the same as in Example 2. Quantum efficiency testing ( Figure 6 This indicates that the materials prepared by this process can achieve efficient conversion of light energy into visible light, with stable quantum efficiency.

[0046] Comparative Example 1 S1, Raw material ratio: Based on With a target composition of 0.2, europium trioxide 0.14g, sodium carbonate 0.10g, calcium carbonate 0.10g, and germanium oxide 0.21g were selected.

[0047] The mixing, grinding, solid-phase reaction and post-processing steps of S2 to S5 are the same as in Example 2. Figure 7 Test results show that a hybrid phase structure appears at this time.

[0048] Comparative Example 2 S1, Raw material ratio: Based on With a target composition of 0.02, europium trioxide 0.014g, sodium carbonate 0.10g, calcium carbonate 0.10g, and germanium oxide 0.21g were selected.

[0049] The mixing, grinding, solid-phase reaction and post-processing steps of S2 to S5 are the same as in Example 2.

[0050] By comparing the test results of samples obtained from different preparation methods ( Figure 8 , Figure 9 It can be seen that, under the same preparation process conditions, [the following will occur]: The doping amount in the raw material ratio is controlled within 0.025 ≤ High-temperature solid-state reactions within the range of ≤0.1 can avoid the adverse effects of local energy accumulation and excessive doping on the stability of the matrix crystal structure, which is beneficial to obtaining rare earth luminescent materials with stable crystal phase and good luminescence response.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing europium-doped germanate red luminescent materials, used to prepare materials with the general chemical formula […]. The red luminescent material, among which This indicates the mole fraction of europium ions doped and 0.025 ≤ ≤0.1, characterized in that, The preparation method includes the following steps: S1. Raw material processing: Weigh sodium carbonate, calcium carbonate, germanium dioxide and europium trioxide according to the stoichiometric ratio of the general chemical formula, mix the weighed raw materials thoroughly and grind them to obtain a mixed powder. S2. High-temperature reaction: After drying the obtained mixed powder, it is placed in a high-temperature furnace and calcined in air atmosphere to cause solid-phase reaction of each raw material. S3. Post-processing: After calcination, the product is cooled to room temperature by furnace cooling and then ground to obtain the red luminescent material.

2. The preparation method according to claim 1, characterized in that, In step S1, the stoichiometric ratio of sodium carbonate, calcium carbonate, germanium dioxide, and europium trioxide is as follows: 。 3. The preparation method according to claim 1, characterized in that, In step S1, the specific process of the grinding treatment is as follows: the fully mixed raw materials are transferred to an agate mortar and wet-grinded using anhydrous ethanol as the dispersion medium for 1-2 hours.

4. The preparation method according to claim 1, characterized in that, In step S2, the mixed powder is naturally air-dried under air conditions.

5. The preparation method according to claim 4, characterized in that, In step S2, the naturally air-dried mixed powder is loaded into a corundum crucible, and the high-temperature furnace is a tube furnace.

6. The preparation method according to claim 1, characterized in that, In step S2, the specific parameters of the calcination process are: heating from room temperature to 850°C at a heating rate of 5°C / min, and holding at 850°C for 6-8 hours.

7. The preparation method according to claim 1, characterized in that, In step S3, the product is cooled to room temperature to form a sintered block, and the sintered block is then crushed and ground.

8. The preparation method according to claim 7, characterized in that, In step S3, the furnace cooling method specifically involves turning off the heating power supply and allowing the product to cool naturally to room temperature inside the furnace.

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