A method for preparing alumina-based luminescent ceramics

Abstract

This invention discloses a novel and efficient method for preparing alumina-based luminescent ceramics, relating to the fields of luminescent materials and ceramics. First, Al₂O₃ nanoparticles are prepared using Al powder. Then, the prepared Al₂O₃ nanoparticles are uniformly mixed with rare earth oxide powder, pressed into blocks, and placed in a graphite pot as an anode for secondary discharge to prepare transparent blocks of alumina-based luminescent ceramics. Depending on the optically active ions doped with, this ceramic can emit strong down-conversion and up-conversion luminescence. This invention offers advantages such as simple method, rapid reaction, low cost, no pollution, high yield, high sample purity, good reproducibility, and no need for catalysts.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to a method for preparing alumina-based luminescent ceramics. Background Technology

[0002] With the continuous research and development of materials chemistry, rare earth doped materials have attracted much attention due to their unique physical properties such as optical, electrical, and magnetic properties, and have shown great application prospects in fields such as lighting, display, catalysis, sensing, optoelectronic devices, and biology.

[0003] Al2O3 possesses excellent mechanical properties, stability, thermochemical properties, high surface area, and low cost, making it a suitable matrix for rare earth (RE) ion doping. It has been widely used as a catalyst support, adsorbent, and ceramic material. Existing technologies have reported numerous methods for preparing Al2O3-based luminescent ceramic materials. For example, Teboho et al. prepared Yb3+ ion-doped Al2O3 ceramics using a solution combustion method. They dissolved aluminum nitrate, ytterbium nitrate, and urea in deionized water and stirred vigorously for 60 minutes. This process was time-consuming, and the ammonia and carbon dioxide produced during urea dissolution generated a pungent odor. Furthermore, the significant exothermic reaction during subsequent combustion led to a high-temperature flame and a violent reaction, posing certain safety hazards (Mokoena TP, Linganiso EC, Swart HC, Kumar V, Ntwaeaborwa OM. Ceramics International. 2017, 43(1, Part A): 174-81.). Takumi et al. used spark plasma sintering (SPS) to prepare C-doped Al2O3 ceramics. The sintering process was carried out in a high-temperature and high-pressure environment for 1 hour. Not only was the reaction process long, but the wide surface of the obtained sample also needed to be mechanically polished afterward, making the processing steps complicated (Kato T, Kawano N, Okada G, Kawaguchi N, Yanagida T. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2018, 435:296-301.). Yang et al. combined gel casting and high-vacuum sintering techniques to prepare Eu2+-doped translucent alumina ceramics. Samples prepared using the gel casting method required drying at room temperature for 24 hours, pre-sintering at 973-1273 K for 3-5 hours, and finally sintering at 2073-2173 K for 5 hours to obtain the desired ceramic sample. This process was cumbersome and dangerous (Y. Yang, H. Wei, L. Zhang, K. Kisslinger, Ch.L. Melcher, Y. Wu, 2015, 168:207-303). In summary, the above methods for preparing alumina-based luminescent ceramics are complex, time-consuming, costly, and have low safety.

[0004] To address the aforementioned issues, this patented technology aims to prepare alumina-based luminescent ceramics using a simple method. On the one hand, it ensures that the alumina doping process with rare earth elements has a short reaction time, low cost, and high yield. On the other hand, it achieves universality in doping different rare earth ions into the Al2O3 matrix. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing rare-earth-doped Al2O3-based luminescent materials, solving the technical problem of the difficulty in preparing rare-earth-doped alumina ceramic luminescent materials in the prior art. The various technical effects of the preferred solutions among the many technical solutions provided by this invention are detailed below.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing rare-earth-doped alumina-based luminescent ceramics, comprising the following steps: Al₂O₃ nanoparticles and rare-earth oxide powders are mixed and placed in a graphite crucible anode within the reaction chamber of a DC arc discharge device; the reaction chamber is evacuated and then filled with argon gas at a pressure of 30-40 kPa; circulating cooling water is introduced through the graphite crucible and the condenser wall; during the discharge process, the voltage is maintained at 5-10 V, the current at 300 A, and the reaction time is 1-3 minutes; the transparent bulk material collected in the graphite crucible is the alumina-based luminescent ceramic. This processing method is simple and convenient, highly efficient and energy-saving, and has a large yield. No catalyst is required during the reaction, and no harmful gases are emitted. The rare-earth-doped alumina-based ceramic luminescent material prepared by this method has high purity, providing more possibilities for the research of rare-earth-doped alumina-based ceramic luminescent materials.

[0008] The aforementioned rare earth oxide powders are one or two of Eu₂O₃, Tb₄O₇, CeO₂, Ho₂O₃, Er₂O₃, Nd₂O₃, and Yb₂O₃. All of these rare earth elements possess good luminescent properties; therefore, products prepared using these rare earth oxides as raw materials have better prospects for applications in the optical field and can provide new research directions for the development of light-emitting devices and ceramic materials.

[0009] As a preferred embodiment of the present invention, the rare earth oxide powder is a mixture of Yb2O3 and one of Ho2O3, Er2O3, and Nd2O3, and the molar ratio of alumina, Yb2O3 and one of the rare earth oxides Ho2O3, Er2O3, and Nd2O3 is 100:2:1.

[0010] Furthermore, the Al2O3 nanoparticles have an α-phase hexagonal structure with a diameter of 50-100 nm. The preparation method is as follows: Al powder is placed in the graphite crucible anode within the reaction chamber of a DC arc discharge device as a reaction raw material; the reaction chamber is evacuated and then filled with oxygen at a pressure of 20 kPa; circulating cooling water is circulated through the graphite crucible and the condenser wall; during the discharge process, the voltage is maintained at 20V and the current at 100A for 3 minutes; the Al2O3 nanoparticles are collected from the condenser wall within the reaction chamber.

[0011] During the discharge process, the reaction chamber is a high-temperature, high-energy environment. The plasma generated by the DC arc under high temperature is crucial for the preparation of Al2O3 nanoparticles. The large specific surface area and uniform particle size distribution of Al2O3 nanoparticles are key to the preparation of dense ceramics. In the second discharge process of this invention, adjusting the experimental parameters to a high current of 300 A and a low voltage of 5-10 V is crucial for the preparation of Al2O3 ceramics. Under these conditions, sufficiently high temperatures are generated on the graphite anode surface, allowing the Al2O3 nanoparticles and rare earth oxides to enter a molten state, thus synthesizing Al2O3-based luminescent ceramics. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0013] Figure 1 This is a schematic diagram of the reaction apparatus used in the method of the present invention;

[0014] Figure 2 This is an XRD image of Al2O3 nanoparticles prepared in Example 1 of this invention;

[0015] Figure 3 This is a SEM image of Al2O3 nanoparticles prepared in Example 1 of this invention;

[0016] Figure 4 This is a SEM image of the Al2O3:Tb3+ ceramic prepared in Example 1 of this invention;

[0017] Figure 5 This is the XRD pattern of Al2O3:Tb3+ prepared in Example 1 of this invention;

[0018] Figure 6 This is the EDS energy spectrum of Al2O3:Tb3+ prepared in Example 1 of this invention;

[0019] Figure 7 This is the PL spectrum of Al2O3:Tb3+ prepared in Example 1 of this invention;

[0020] Figure 8This is a SEM image of the Al2O3:Ce3+ ceramic prepared in Example 2 of this invention;

[0021] Figure 9 This is the XRD pattern of Al2O3:Ce3+ prepared in Example 2 of this invention;

[0022] Figure 10 This is the EDS energy spectrum of Al2O3:Ce3+ prepared in Example 2 of this invention;

[0023] Figure 11 This is the PL spectrum of Al2O3:Ce3+ prepared in Example 2 of this invention;

[0024] Figure 12 This is the XRD pattern of Al2O3:Eu2+ prepared in Example 3 of this invention;

[0025] Figure 13 This is the EDS energy spectrum of Al2O3:Eu2+ prepared in Example 3 of this invention;

[0026] Figure 14 This is the PL spectrum of Al2O3:Eu2+ prepared in Example 3 of this invention;

[0027] Figure 15 This is the XRD pattern of Al2O3:Yb3+, Ho3+ prepared in Example 5 of this invention;

[0028] Figure 16 This is the EDS energy spectrum of Al2O3:Yb3+, Ho3+ prepared in Example 5 of this invention;

[0029] Figure 17 This is the PL spectrum of Al2O3:Yb3+, Ho3+ prepared in Example 5 of this invention;

[0030] Figure 18 This is an XRD image of Al2O3:Yb3+,Er3+ prepared in Example 6 of this invention;

[0031] Figure 19 This is the EDS energy spectrum of Al2O3:Yb3+,Er3+ prepared in Example 6 of this invention;

[0032] Figure 20 This is the PL spectrum of Al2O3:Yb3+,Er3+ prepared in Example 6 of this invention;

[0033] Figure 21 This is the XRD pattern of Al2O3:Yb3+,Nd3+ prepared in Example 7 of this invention;

[0034] Figure 22This is the EDS energy spectrum of Al2O3:Yb3+,Nd3+ prepared in Example 7 of this invention;

[0035] Figure 23 This is the PL spectrum of Al2O3:Yb3+,Nd3+ prepared in Example 7 of this invention;

[0036] Figure 24 This is a SEM image of Al2O3:Yb3+, Ho3+ prepared in Example 8 of this invention;

[0037] Figure 25 This is the XRD pattern of Al2O3:Yb3+, Ho3+ prepared in Example 8 of this invention;

[0038] Figure 1 In the middle: 1. Reaction chamber; 2. Condensation wall; 3. Tungsten cathode; 4. Reaction raw materials; 5. Graphite crucible anode; 6. Copper base (including water inlet and water outlet); 7. Gas inlet; 8. Gas outlet; 9. Condensation wall water inlet; 10. Condensation wall water outlet. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] Figure 1 This is a schematic diagram of the reaction apparatus used in the method of the present invention.

[0041] like Figure 1 As shown, reaction chamber 1 is enclosed by condenser wall 2, tungsten rod cathode 3, and graphite crucible anode 5. The side of graphite crucible anode 5 opposite to tungsten rod cathode 3 is filled with reactant material 4. An arc is formed between graphite crucible anode 5 and tungsten rod cathode 3 by controlling the raising and lowering of copper base 6. To ensure the smooth condensation of the reaction product, circulating cooling water is introduced into graphite crucible anode 5 and condenser wall 2. Copper base 6 serves as both inlet and outlet, and cooling water circulates through inlet 9 and outlet 10 in condenser wall 2. Before and after the reaction, reaction gas is introduced through inlet 7 and outlet 8 for gas washing, filling, and passivation. Finally, the product is obtained at graphite crucible anode 5.

[0042] Example 1

[0043] like Figure 2-7 As shown, this embodiment prepared an Al2O3:Tb3+ ceramic luminescent material. The material preparation process is as follows:

[0044] Aluminum powder was pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm in a tableting mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, and a tungsten rod cathode 3 was fixed at a certain distance above the reactant 4. The reaction chamber 1 was evacuated, and oxygen was introduced into it as the reaction gas. The circulating water device was turned on, and cooling water was introduced through the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten rod 3 made contact momentarily, instantly igniting an arc for discharge. During the discharge process, the voltage was maintained at 20 V, the current at 100 A, and the reaction time was 3 min. The sample collected on the condenser wall consisted of Al2O3 nanoparticles. Figure 2 The image shows the XRD pattern of Al2O3 nanoparticles. All diffraction peaks correspond to the hexagonal structure of Al2O3, indicating that the prepared nanoparticles are very pure. Figure 2 The image shows a SEM image of the Al2O3 nanoparticles, which are regular spherical in shape with a diameter of 50-100 nm.

[0045] The Al2O3 nanoparticles and Tb4O7 powder were then mixed uniformly at a ratio of 100:1 and pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm in a pressing mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. The reaction chamber 1 was evacuated to a vacuum, and argon gas was repeatedly introduced into the chamber to remove oxygen and water from the reaction device. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 made contact momentarily, instantly igniting an arc and initiating discharge. During the discharge process, the voltage was maintained at 8 V, the current at 300 A, and the reaction time was 2 min. A translucent ceramic sample was obtained in the graphite crucible, which is the Tb-doped aluminum nitride ceramic luminescent material. Figure 3 This is a SEM image of the alumina-doped Tb3+ ceramic luminescent material. The SEM image shows the high-density microstructure of the alumina-based ceramic sample, with uniform and equiaxed grains and no obvious pores. Figure 4 The XRD pattern of the Tb3+-doped ceramic luminescent material is shown. All diffraction peaks correspond to the hexagonal structure of Al2O3. No other Tb-related crystal phases were detected in the XRD pattern, indicating that the sample has high purity. Figure 5 The EDS spectrum of this alumina-doped Tb3+ ceramic luminescent material is shown. Figure 6 The image shows the photoluminescence (PL) spectrum of this alumina ceramic luminescent material under 468 nm excitation. It can be seen that the Tb³⁺-doped alumina-based ceramic luminescent material emits yellow light at 551 nm under 283 nm excitation. Figure 4In the excitation spectrum, the spectrum extends from 250 nm to 500 nm, with obvious peaks at 283 nm, 327 nm, 375 nm, and 468 nm. The excitation peak at 283 nm is due to the 4f8-4f75d1 transition of Tb3+ ions, the excitation peak at 327 nm is due to the 7F6-5H7 transition of Tb3+ ions, the 375 nm peak is due to the 7F6-5D2 transition of Tb3+ ions, and the 468 nm peak is due to the 7F6-5D4 transition of Tb3+ ions.

[0046] Example 2

[0047] like Figure 8-11 As shown, this embodiment prepared an Al2O3:Ce3+ ceramic luminescent material. The material preparation process is as follows:

[0048] Following the same steps as in Case 1, Al2O3 nanoparticles were collected on the condenser wall. These Al2O3 nanoparticles were then mixed with CeO2 powder at a ratio of 100:1 and pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm using a pressing mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of the DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. The reaction chamber 1 was evacuated to a vacuum, and argon gas was repeatedly introduced into the chamber to remove oxygen and water from the reaction device. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 came into contact and an arc was ignited for discharge. During the discharge process, the voltage was maintained at 10V and the current at 300A for 2 minutes. A translucent ceramic sample was obtained in the graphite crucible, which is a cerium-doped aluminum nitride ceramic luminescent material. Figure 8 This is a SEM image of the cerium-doped aluminum nitride ceramic luminescent material. The SEM image shows the high-density microstructure of the alumina-based ceramic sample, with uniform and equiaxed grains and no obvious pores. Figure 9 The XRD pattern of the cerium-doped aluminum nitride ceramic luminescent material is shown. All diffraction peaks correspond to the hexagonal structure of Al2O3. No other Ce-related crystal phases were detected in the XRD pattern, indicating that the sample has high purity. Figure 10 This is the EDS energy spectrum of the material. Figure 11 The image shows the photoluminescence (PL) spectrum of this Ce-doped alumina ceramic luminescent material under 309 nm excitation. Figure 11 In the excitation spectrum, the maximum emission value is at 451 nm, and the maximum excitation value is at 309 nm. The excitation at 310 nm corresponds to the 4f-5d transition, and the emission at 458 nm corresponds to the 5d-4f electronic transition.

[0049] Example 3

[0050] like Figure 12-14 As shown, this embodiment prepared an Al2O3:Eu2+ ceramic luminescent material. The material preparation process is as follows:

[0051] Following the same steps as in Case 1, Al2O3 nanoparticles were collected on the condenser wall. This alumina nanoparticle powder was then mixed with europium oxide powder at a ratio of 100:1 and pressed into an ingot 4 with a diameter of 1.8 cm and a height of 2 cm using a pressing mold. The ingot 4 was placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. After evacuating the reaction chamber 1 to a vacuum, argon gas was repeatedly introduced into the reaction chamber 1 to remove oxygen and water from the reaction device. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 came into contact and an arc was ignited for discharge. During the discharge process, the voltage was maintained at 5 V, the current at 300 A, and the reaction time was 1 min. A translucent ceramic sample was obtained in the graphite crucible, which is the Eu2+-doped aluminum nitride ceramic luminescent material. Because the divalent oxidation state of Eu ions becomes favorable under low oxygen partial pressure, Figure 12 The XRD pattern of the alumina-doped Eu2+ ceramic luminescent material is shown. All diffraction peaks correspond to the hexagonal structure of Al2O3. No other Eu-related crystal phases were detected in the XRD pattern, indicating that the sample has high purity. Figure 13 The figure shows the EDS spectrum of the alumina-based luminescent material, and the PL spectrum of the alumina-doped Eu2+ ceramic luminescent material is also shown. Figure 14 In the translucent ceramic, the broad emission band of Eu2+-doped alumina centered at 520 nm, which emits blue light, is due to the energy level transition from 4f65d1 to 4f7.

[0052] Example 4

[0053] like Figure 15-17 As shown, this embodiment prepared an Al2O3:Yb3+,Ho3+ ceramic luminescent material. The material preparation process is as follows:

[0054] Following the same steps as in Case 1, Al2O3 nanoparticles were collected on the condenser wall. These Al2O3 nanoparticles, Ho2O3, and Yb2O3 were mixed uniformly at a ratio of 100:1:2 and then pressed into an ingot 4 with a diameter of 1.8 cm and a height of 2 cm using a pressing mold. The ingot 4 was placed in a graphite crucible 5 within the reaction chamber of the DC arc discharge device, and a tungsten rod cathode 3 was fixed at a certain distance above the reactant material 4. After evacuating the reaction chamber 1 to a vacuum, argon gas was repeatedly introduced into the reaction chamber 1 to remove oxygen and water from the reaction device. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten rod 3 came into contact and an arc was ignited for discharge. During the discharge process, the voltage was maintained at 4 V, the current at 300 A, and the reaction time was 2 min. A translucent ceramic sample was obtained in the graphite crucible, which is the upconversion Al2O3:Yb3+, Ho3+ ceramic luminescent material. Figure 15 The image shows the XRD pattern of this alumina ceramic luminescent material. The diffraction peaks of this alumina-based ceramic luminescent material can be identified as belonging to hexagonal alumina. Figure 16 The EDS spectrum of this alumina ceramic luminescent material is shown. Quantitative analysis using EDS reveals an Al:O:Ho:Yb atomic ratio of approximately 23.4:43.78:0.25:0.58. Figure 17 The photoluminescent spectrum of this alumina ceramic material under 980 nm excitation shows obvious peaks at 550 nm, 668 nm, and 759 nm. The emission peak at 550 nm is due to the transition of Ho3+ ions from 5F4 to 5S2 to 5I8, the emission peak at 668 nm is due to the transition of Ho3+ ions from 5F5 to 5I8, and the emission peak at 759 nm is due to the transition of Ho3+ ions from 5F4 to 5S2 to 5I7.

[0055] Example 5

[0056] like Figure 18-20 As shown, this embodiment prepared an Al2O3:Yb3+,Er3+ ceramic luminescent material. The material preparation process is as follows:

[0057] Following the same steps as in Case 1, Al2O3 nanoparticles were collected on the condenser wall. These Al2O3 nanoparticles were then mixed with Er2O3 and Yb2O3 powders at a ratio of 100:1:2 and pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm using a pressing mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of the DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. The reaction chamber 1 was evacuated to a vacuum, and argon gas was repeatedly introduced into the chamber to remove oxygen and water from the reaction device. Then, 30 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 came into contact and an arc was ignited for discharge. During the discharge process, the voltage was maintained at 10 V, the current at 300 A, and the reaction time was 2 min. A translucent ceramic sample was obtained in the graphite crucible, which is the Al2O3:Yb3+, Er3+ aluminum nitride ceramic luminescent material. Figure 18 The image shows the XRD pattern of the Al2O3 ceramic luminescent material. The diffraction peaks of this Al2O3-based ceramic luminescent material are attributed to hexagonal alumina. Figure 19 The EDS spectrum of this alumina ceramic luminescent material is shown. Quantitative analysis using EDS reveals an Al:O:Er:Yb atomic ratio of approximately 38.4:40.6:0.6:1.27. Figure 20 The PL spectrum of this alumina ceramic luminescent material under 980 nm excitation shows green emission bands at 525 nm, 543 nm, and 556 nm, and a predominant red emission band at 665 nm. The emission spectrum extends to 800 nm. The spectrum has obvious peaks at 525 nm, 543 nm, 556 nm, and 665 nm. The emission peak at 525 nm is due to the 2H11 / 2-4I15 / 2 transition of Er3+ ions, the emission peak at 543 nm is due to the 4S11 / 2-4I15 / 2 transition of Er3+ ions, and the emission peak at 556 nm is due to the 4F9 / 2-4I15 / 2 transition of Er3+ ions.

[0058] Example 6

[0059] like Figure 21-23 As shown, this embodiment prepared an Al2O3:Yb3+,Nd3+ ceramic luminescent material. The material preparation process is as follows:

[0060] Following the same steps as in Case 1, Al2O3 nanoparticles were collected on the condenser wall. These nanoparticles were then mixed with Nd2O3 and Yb2O3 powders at a ratio of 100:1:2 and pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm using a pressing mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. The reaction chamber 1 was evacuated to a vacuum, and argon gas was repeatedly introduced into the chamber to remove oxygen and water from the reaction apparatus. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water system was turned on, and cooling water was introduced from the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 came into contact and an arc was ignited for discharge. During the discharge process, the voltage was maintained at 6 V, the current at 300 A, and the reaction time was 1 min. A translucent ceramic sample was obtained in the graphite crucible, which is the Al2O3:Yb3+,Nd3+ ceramic luminescent material. Figure 21 The image shows the XRD pattern of this alumina ceramic luminescent material. The diffraction peaks of this Al2O3-based ceramic luminescent material are attributed to hexagonal alumina. Figure 22 The EDS spectrum of this alumina ceramic luminescent material is shown. Quantitative analysis using EDS reveals an Al:O:Nd:Yb atomic ratio of approximately 33.79:40.93:0.3:0.59. Figure 23 The photoluminescence (PL) spectrum of this alumina ceramic luminescent material under 980 nm excitation shows a green emission band at 539 nm, an orange emission band at 598 nm, a red emission band at 666 nm, and near-infrared emission at 751 nm, 801 nm, and 863 nm. The appearance of the new visible light emission band and the enhancement of near-infrared luminescence intensity indicate effective electron transfer between Nd3+ and Yb3+. Extending the emission spectrum to 800 nm, the PL spectrum corresponds to the 2G9 / 2,4G7 / 2-4I9 / 2 electronic transition of Nd3+ ions at 539 nm, the 2G9 / 2,4G7 / 2-4I11 / 2 electronic transition of Nd3+ ions at 598 nm, and the 2G9 / 2,4G7 / 2-4I13 / 2 electronic transition of Nd ions at 666 nm. The near-infrared wavelengths of 751 nm, 801 nm, and 863 nm are due to energy level transitions of 2S3 / 2,4F7 / 2-4I9 / 2, 2H9 / 2,4F5 / 2-4I9 / 2, and 2H9 / 2,4F3 / 2-4I9 / 2, respectively.

[0061] Example 8

[0062] like Figure 24-25 As shown, this embodiment prepared an Al2O3:Yb3+,Ho3+ luminescent material. The material preparation process is as follows:

[0063] Al₂O₃, Nd₂O₃, and Yb₂O₃ powders were mixed evenly in a ratio of 100:1:2 and then pressed into ingots 4 with a diameter of 1.8 cm and a height of 2 cm in a pressing mold. The ingots 4 were placed in a graphite crucible 5 within the reaction chamber of a DC arc discharge device, and a tungsten cathode 3 was fixed at a certain distance above the reactant material 4. The reaction chamber 1 was evacuated to a vacuum, and argon gas was repeatedly introduced into the chamber to remove oxygen and water from the reaction device. Then, 40 kPa argon gas was introduced as the reaction gas. The circulating water device was turned on, and cooling water was introduced through the copper base 6 and the condenser wall 2. The height of the copper base 6 was adjusted so that the graphite crucible 5 and the tungsten cathode 3 made contact momentarily, instantly igniting an arc and initiating discharge. During the discharge process, the voltage was maintained at 20 V, the current at 120 A, and the reaction time was 3 min. The sample obtained in the graphite crucible is a holmium and ytterbium-doped aluminum nitride powder luminescent material. Figure 24 This is a SEM image of the alumina ceramic luminescent material, which shows the irregular blocky structure of the sample. Figure 25 The image shows the XRD pattern of the alumina ceramic luminescent material. It can be seen from the image that the diffraction peaks of the alumina-based ceramic luminescent material belong to hexagonal alumina.

[0064] This case illustrates that the sample prepared under the experimental conditions of the conventional DC arc method is an irregular alumina particle. Only under the experimental conditions of the patented high current of 300 A and low voltage of 5 ~ 10 V, the temperature of the graphite crucible is increased, causing the material inside to reach a molten state. Under these conditions, a translucent alumina-based luminescent ceramic material can be prepared.

[0065] This application uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions presented in this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for preparing an alumina-based luminescent ceramic, characterized in that, Includes the following steps: Al2O3 nanoparticles and rare earth oxide powders were mixed and placed in a graphite crucible anode located in the reaction chamber of a DC arc discharge device. After the reaction chamber is evacuated, it is filled with argon gas at a pressure of 30-40 kPa. Circulating cooling water is introduced into the graphite pot and the condenser wall. During the discharge process, the voltage is maintained at 5-10 V and the current at 300 A, and the reaction time is 1-3 minutes. The transparent bulk material collected in the graphite pot is alumina-based luminescent ceramic. The rare earth oxide powder is a mixture of Yb2O3 and one of Ho2O3, Er2O3, and Nd2O3, and the molar ratio of Al2O3, Yb2O3 and one of Ho2O3, Er2O3, and Nd2O3 is 100:2:1; The Al2O3 nanoparticles have an α-phase hexagonal structure.

2. The method for preparing alumina-based luminescent ceramics according to claim 1, characterized in that, The Al2O3 nanoparticles have a diameter of 50-100 nm.

3. The method for preparing alumina-based luminescent ceramics according to claim 2, characterized in that, The preparation method of the Al2O3 nanoparticles is as follows: (1) Place Al powder into the graphite crucible anode in the reaction chamber of the DC arc discharge device as a reaction raw material; (2) After the reaction chamber is evacuated, oxygen is introduced into it at a pressure of 20 kPa. Circulating cooling water is introduced into the graphite pot and the condenser wall. During the discharge process, the voltage is maintained at 20V and the current at 100A for 3 minutes. (3) Collect Al2O3 nanoparticles on the condenser wall in the reaction chamber.

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