A fluorescent powder with multi-mode light emission and anti-thermal quenching performance and a preparation method thereof

Abstract

The application provides a fluorescent powder with multimode light emission and anti-thermal quenching performance, relates to the field of inorganic luminescent materials, and the fluorescent powder material takes Mg4Ta2O9 as a substrate, introduces trivalent rare earth ions RE through heterovalent substitution 3+ Monovalent alkali metal ions M are introduced as light emission centers + As a charge compensator, the trap level distribution and defect concentration in the substrate material are accurately controlled, the synergistic output of four modes of photoluminescence, radioluminescence, thermoluminescence and long afterglow luminescence is realized; meanwhile, the fluorescent powder material can respond to ultraviolet light, X-rays and other external excitation, exhibits excellent visible spectrum emission characteristics, and keeps stable light emission in a high-temperature environment, is suitable for wide application fields and has excellent performance.

Description

Technical Field

[0001] This invention relates to the field of inorganic luminescent materials technology, and in particular to a phosphor with multimode luminescence and heat quenching resistance, and its preparation method. Background Technology

[0002] In recent years, with the rapid development of digitalization and the Internet of Things (IoT) technologies, security issues such as product counterfeiting, information theft, and identity fraud have become increasingly serious, creating an urgent need for high-security anti-counterfeiting and encryption technologies. Currently, mainstream anti-counterfeiting technologies include holographic labels, fluorescent inks, QR codes, and radio frequency identification (RFID). Among these, fluorescent anti-counterfeiting materials based on optical response have been widely used in currency, documents, and brand packaging due to their advantages of good concealment, convenient detection, and low cost. For example, under ultraviolet light, fluorescent ink emits visible light of a specific color, enabling rapid authentication. However, traditional optical anti-counterfeiting technologies often rely on single static luminescence characteristics (such as a single emission color at a fixed excitation wavelength). Their optical modes are simple, their encoding capacity is limited, and they are easily scanned, copied, and counterfeited with high precision. Their security is insufficient to meet the current demands for high-level information security.

[0003] To overcome the aforementioned bottlenecks and address the problems of traditional optical anti-counterfeiting relying on a single static emission feature (i.e., a fixed excitation-emission mode), which results in simple optical modes, limited coding capacity, susceptibility to high-precision scanning and copying, and insufficient security, existing technologies typically employ multi-excitation / multi-emission composite dynamic fluorescence anti-counterfeiting schemes. This involves combining two or more fluorescent materials with different excitation responses to achieve a dynamic effect where "different excitation wavelengths correspond to different emission colors / intensities," thereby elevating the anti-counterfeiting dimension from single-bit to multi-bit. However, this method has a low barrier to counterfeiting and completely fails in high-security scenarios (i.e., counterfeiters do not need to crack the original formula; they can reverse engineer it simply by combining commercially available single-excitation phosphors). Furthermore, the lightfastness, decay rate, and weather resistance of different phosphors in the composite system are completely different, causing the brightness ratio of the two excitation channels to shift after long-term storage, resulting in complete failure of the anti-counterfeiting feature and poor long-term consistency and stability.

[0004] Meanwhile, existing technologies also include multi-stimulus responsive fluorescent anti-counterfeiting schemes, which involve developing materials that produce specific luminescent responses to various external stimuli other than light (such as heat, force, humidity, pH, X-rays, etc.). However, this method suffers from severe signal cross-interference, high misjudgment rate (the signals of most multi-stimulus responsive materials have severe cross-influence, making it impossible to form a unified and standardized rule for determining authenticity), poor cycle stability and environmental stability, uncontrollable performance, and failure due to mutual influence of multi-mode responses. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a phosphor with multimode luminescence and thermal quenching resistance. This phosphor material uses a structurally stable inorganic compound as a matrix, and through directional doping with rare earth activating ions and co-doping with alkali metal ions as charge compensators, it precisely controls the trap energy level distribution and defect concentration within the material, achieving synergistic output of four modes: photoluminescence, radiative luminescence, thermoluminescence, and long-afterglow luminescence. This phosphor material can respond to various external excitations such as ultraviolet light and X-rays, exhibiting excellent visible spectrum emission characteristics, and maintains stable luminescence at high temperatures, making it suitable for advanced information encryption and anti-counterfeiting applications.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned phosphor, which is used to prepare a phosphor with multi-mode luminescence (i.e., photoluminescence, radiative luminescence, thermoluminescence, and long afterglow luminescence) and thermal quenching resistance.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A phosphor with multimode luminescence and resistance to thermal quenching, the phosphor material having the chemical composition of Mg. 4-x%-y% Ta2O9:x%RE 3+ ,y%M + In this context, RE represents any one of the four rare earth elements: Pr (praseodymium), Tb (terbium), Dy (dysprosium), and Tm (thulium), and M represents any one of the two alkali metal elements: Li (lithium) and Na (sodium).

[0009] Based on further optimization of the above scheme, x% of the rare earth activation ions doped with the phosphor are trivalent rare earth activation ions (RE). 3+ Replacement of Mg in the matrix 2+ The molar percentage of lattice sites is 0.2 ≤ x ≤ 2 when RE is Pr, 0.1 ≤ x ≤ 5 when RE is Tb, 1 ≤ x ≤ 6 when RE is Dy, and 0.1 ≤ x ≤ 1.5 when RE is Tm; y% of the phosphor-doped alkali metal ions represents monovalent alkali metal charge-compensating ions M. + Replacement of Mg in the matrix 2+ The molar percentage of lattice sites, 1≤y≤9.

[0010] Preferably, among the rare earth activation ions doped with phosphor, when RE is Pr, x=0.4; when RE is Tb, x=0.3; when RE is Dy, x=4; when RE is Tm, x=0.1; and y=5.

[0011] This invention utilizes Mg4Ta2O9, which has a hexagonal corundum-type layered structure, as the sole matrix, and leverages the Mg in its structure... 2+ Lattice sites, introducing trivalent rare earth ions (REs) through heterovalent substitution3+ As the luminescent center, monovalent alkali metal ions M are introduced simultaneously. + As a charge compensator, it repairs charge imbalances and lattice defects caused by heterovalent substitution. By controlling defect engineering, the depth and density distribution of traps in the material are optimized, thereby integrating four emission modes: photoluminescence, radiative emission, thermoluminescence, and long afterglow emission, with the emission spectrum covering the entire visible light spectrum from 400 to 800 nm. At the same time, it endows the material with thermal quenching resistance, maintaining or even enhancing its intensity over a wide temperature range (298 K to 523 K), and simultaneously improving quantum efficiency, luminescence intensity, and X-ray afterglow duration through charge compensation.

[0012] A method for preparing a phosphor with multimode emission and thermal quenching resistance, used to prepare the aforementioned multimode emission phosphor material, comprising: Step S1, preparation of supercritical fluid-assisted precursor: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3, and homologous MNO3 (molten salt medium) according to the material matching rules, and add them to the high-pressure reactor. Use anhydrous ethanol as a dispersant and seal the reactor. Then, use supercritical CO2 fluid to achieve ultrafine dispersion and surface activation of the raw materials, and simultaneously complete the pre-decomposition of the precursor to obtain precursor powder. Step S2, Gradient Pre-calcination: The precursor powder from Step S1 is subjected to a first-stage calcination (removing moisture and residual ethanol) and a second-stage calcination (complete melting of the homologous MNO3 molten salt medium to form a uniform liquid medium, wetting the high-melting-point Ta2O5 and mesophase particles, so that RE...) in a muffle furnace. 3+ M + Molecular-level diffusion is achieved in a liquid medium, with in-situ pre-assembly in Mg. 2+ The gradient calcination process involves replacing the doping site with the adjacent charge compensation site to achieve precise pre-positioning of the doping site, and the third stage calcination (the nitrogen oxides and oxygen generated by the complete decomposition of the MNO3 molten salt medium are discharged, leaving only M2O that is homologous with the charge compensation agent, which merges with the M2O generated by the decomposition of M2CO3 in the raw material; at the same time, the carbonate is completely decomposed to avoid the volatilization of alkali metals and crucible creep during subsequent high-temperature sintering). Step S3, multi-temperature gradient sintering: First, the pre-calcined powder is pressed into a green blank (to ensure close contact between powder particles and improve solid-phase diffusion efficiency); then the green blank is placed in a superconducting high magnetic field programmable sintering furnace with the magnetic field direction perpendicular to the green blank base surface (i.e., the upper and lower end surfaces of the pressed green blank). Under normal atmospheric pressure and air atmosphere, the high magnetic field is turned on throughout the process to sequentially carry out directional site occupancy pre-crystallization, trap energy level control, lattice crystallization and trap locking. Step S4, Surface passivation: First, grind the sintered green blank, and then perform oxygen plasma treatment; Step S5, Annealing treatment: The powder after oxygen plasma treatment is annealed (to eliminate active oxygen species on the surface and eliminate non-radiative complex active sites on the surface), and then naturally cooled to room temperature to obtain the final product.

[0013] Based on further optimization of the above scheme, in step S1, the molar amount of MgO is (4-xy)·A, the molar amount of Ta2O5 is 2·A, the molar amount of RE2O3 is (x / 2)·A, the molar amount of M2CO3 is [(y-Δy) / 2]·A, and the molar amount of homologous MNO3 (molten salt medium) is Δy·A; where A represents the molar basis coefficient for ingredient addition, in mol; Δy is the amount of MNO3 provided by the molten salt medium. + The molar amount accounts for the total M + The proportionality constant of molar quantities, Δy = k·y, and is required to satisfy Δy <y,k=15%~25%。

[0014] Based on further optimization of the above scheme, in step S1, the volume-to-mass ratio of anhydrous ethanol to all materials is 5-6 mL: 1 g.

[0015] Based on further optimization of the above scheme, in step S1, supercritical CO2 fluid is used to achieve ultrafine dispersion and surface activation of the raw materials, and the precursor pre-decomposition is completed simultaneously to obtain precursor powder. The specific steps are as follows: First, high-purity CO2 gas (purity ≥99.9%) is introduced into the high-pressure reactor at a rate of 5-10 mL / min, the temperature is raised to 39-41℃, the pressure inside the reactor is adjusted to 9.8-10.2 MPa (so that CO2 reaches the supercritical state), and the reaction is carried out at a rotation speed of 290-310 rpm, 195-205 W, and 40 kHz external current. Under ultrasound, maintain for 28–32 min (to achieve nanoscale monodispersion and surface activation of the raw material); then, maintain the supercritical state, increase the temperature to 345–355℃ at 5–6℃ / min, increase the pressure to 24.5–25.5MPa at 0.8–1MPa / min, and hold at the temperature and pressure for 0.9–1.1 h (to complete the pre-decomposition of the precursor); finally, depressurize at 9.5–10.5MPa / s to 4.5–5.5MPa, and then depressurize at 0.4–0.5MPa / s to atmospheric pressure to obtain a precursor powder with no hard agglomerates and nanoscale monodispersion.

[0016] Based on further optimization of the above scheme, in step S2, the first stage of calcination specifically involves: heating to 195–205℃ at a rate of 4.5–5.5℃ / min under normal pressure air atmosphere and holding for 0.9–1.1h; the second stage of calcination specifically involves: heating to 345–355℃ at a rate of 4.5–5.5℃ / min under normal pressure air atmosphere and holding for 2.9–3.1h; the third stage of calcination specifically involves: heating to 595–605℃ at a rate of 9.5–10.5℃ / min under normal pressure air atmosphere and holding for 1.9–2.1h, with dry air continuously introduced at a flow rate of 20–30 sccm during the calcination process. Nitrates of the same origin as the charge compensator are used as the molten salt to avoid introducing foreign impurities, while the total M is strictly locked through material matching. + The content ensures that the chemical structure and content of the product remain completely unchanged; the low-temperature molten salt breaks through the solid-phase diffusion barrier of high-melting-point tantalates, realizing RE 3+ With M + Molecular-level uniform dispersion and site pre-assembly enhance M + Lattice doping rate, eliminating fluctuations in charge compensation effect between batches.

[0017] Based on further optimization of the above scheme, in step S3, pressing the pre-calcined powder into a blank specifically involves placing the pre-calcined powder in a stainless steel mold and pressing it into a circular blank with a diameter of 20±1mm and a thickness of 3±0.5mm under a unidirectional pressure of 19.5~20.5MPa.

[0018] Based on further optimization of the above scheme, in step S3, the magnetic field strength of the superconducting high magnetic field programmable sintering furnace is 11.5–12 T; the directional site-occupying pre-crystallization specifically involves heating to 795–805 °C at a rate of 4.5–5.5 °C / min and holding at that temperature for 3.9–4.1 h. At this temperature, the main phase of Mg4Ta2O9 begins to nucleate, and the strong static magnetic field regulates RE through the Zeeman effect. 3+ The 4f electron spin state reduces RE 3+ In Mg 2+ The substitution barrier at the site induces RE 3+ Directional substitution of Mg 2+ Sites, inhibiting their occupation of Ta 5+ Site, simultaneously inducing M + Simultaneous entry into adjacent charge compensation sites enhances RE. 3+ Site occupancy accuracy and doping uniformity.

[0019] Based on further optimization of the above scheme, in step S3, the trap energy level control specifically involves: heating to 1045–1055℃ at a rate of 2.5–3.5℃ / min and holding at this temperature for 5.9–6.1 h. At this temperature, the lattice is in a semi-relaxed state, which can precisely generate a double-trap energy level structure: shallow traps (0.6–0.8 eV, corresponding to X-ray afterglow and photo-induced luminescence) and deep traps (0.9–1.3 eV, corresponding to thermal quenching resistance; at high temperatures, the carriers trapped in deep traps are thermally activated and released, compensating for the non-radiative recombination loss caused by temperature rise, and achieving stable luminescence over a wide temperature range); simultaneously, the trap density is quantitatively controlled through the synergistic effect of heat preservation and a strong static magnetic field, avoiding trap merging and annihilation at high temperatures.

[0020] Based on further optimization of the above scheme, in step S3, lattice crystallization specifically involves heating to 1245–1255℃ at a rate of 4.5–5.5℃ / min and holding at that temperature for 1.9–2.1 hours. This stage achieves complete lattice crystallization and eliminates non-radiative recombination centers caused by lattice distortion. Simultaneously, short-time high-temperature sintering combined with a strong static magnetic field completely suppresses anisotropic abnormal growth of the hexagonal lattice along the (001) basal plane, ensuring grain size stability and avoiding the formation of abnormal grains such as plate-like or rod-like structures.

[0021] Based on further optimization of the above scheme, in step S3, the trap locking specifically involves: first, cooling to 895–905°C at a rate of 1.8–2.2°C / min and holding at that temperature for 2.9–3.1 hours; then cooling to 595–605°C at a rate of 0.8–1.2°C / min, followed by furnace cooling to room temperature, with the strong magnetic field maintained until the temperature drops below 595°C and then shut off. This gradient cooling process allows the trap energy levels to form a stable thermodynamic equilibrium state in the crystal lattice, avoiding trap annihilation and structural instability caused by rapid cooling.

[0022] Based on further optimization of the above scheme, in step S4, the sintered green blank is placed in an agate mortar for light grinding and passed through a 300-mesh sieve to obtain fluorescent powder. The oxygen plasma treatment process is as follows: First, the powder is evenly spread on a quartz tray (thickness ≤ 0.5 mm), placed in a radio frequency plasma reaction chamber, and evacuated to a base pressure of 9–10 Pa. Then, high-purity oxygen is introduced at a flow rate of 48–52 sccm, and the chamber pressure is stabilized at 29–31 Pa. Finally, a 13.56 MHz radio frequency power supply is turned on, and the power is adjusted to 48–52 W (low-energy mode to avoid surface etching and bulk structure damage). The treatment is carried out at room temperature for 4–6 minutes (i.e., the powder remains at room temperature throughout the process, without high-temperature phase transition). The low-energy oxygen plasma acts on 1–2 atomic layers of the powder surface without changing the bulk chemical composition, crystal structure, or trap energy levels. Active oxygen atoms combine with dangling bonds and unsaturated coordination sites on the powder surface, repairing surface lattice defects and forming complete Mg-O and Ta-O lattice terminals, eliminating surface non-radiative recombination centers, and simultaneously preventing the erosion of the powder surface by water vapor and carbon dioxide in the air.

[0023] Based on further optimization of the above scheme, the annealing process is specifically as follows: the powder after oxygen plasma treatment is immediately placed in a programmable muffle furnace and held at 195-205°C for 28-32 minutes under normal air pressure for low-temperature annealing.

[0024] The following are the technical effects of this solution: This invention's phosphor system breaks through the bottleneck of single static luminescence, achieving synergistic output of four modes: photoluminescence, radiative luminescence, thermoluminescence, and long afterglow. The emission spectrum covers the visible light range of 400–800 nm, enhancing the anti-counterfeiting dimension from single-bit to multi-bit, with an order-of-magnitude increase in coding capacity and a high threshold for counterfeiting. Simultaneously, it solves the problem of long-term failure in compound systems. The single matrix system used has no multi-component attenuation differences, and the anti-counterfeiting features do not shift after long-term storage, significantly extending its lifespan. Furthermore, this invention achieves multi-mode response solely through light (254 nm, 310 nm, and 365 nm ultraviolet and X-ray excitation) and thermal stimulation, with no signal cross-interference, enabling the formation of standardized rules for authenticity determination and resulting in an extremely low false positive rate. The phosphor prepared by this invention, through precise control of deep trap energy levels, maintains a luminescence intensity retention rate of ≥90% at 523K relative to room temperature (298K) within a wide temperature range of 298K to 523K (room temperature to 250℃). Furthermore, it exhibits an increase in luminescence intensity with increasing temperature, solving the industry pain point of rapid luminescence drop in traditional phosphors at high temperatures. This makes it suitable for special scenarios such as anti-counterfeiting and detection in high-temperature environments. The phosphor prepared by this invention achieves an internal quantum efficiency of ≥85% under ultraviolet excitation, X-ray excitation yield of ≥30000 ph / MeV, long afterglow duration of ≥12h (i.e., the afterglow duration after X-ray excitation stops), and thermoluminescent cycling stability of ≥1000 cycles without significant attenuation. Simultaneously, the entire process parameters are controllable, exhibiting excellent batch stability and suitability for large-scale industrial production. It can be widely applied in various fields such as advanced anti-counterfeiting, information encryption, radiation detection, and emergency lighting.

[0025] In terms of preparation method, this invention effectively solves the problems of primary hard agglomeration of Ta2O5, micron-level uneven mixing of raw materials, and local agglomeration of dopant ions by using supercritical fluid-assisted precursor preparation, thus avoiding local agglomeration and impurity phase formation during subsequent high-temperature sintering; it solves the problems of time difference between alkali metal melting-volatilization and lattice doping, batch failure of charge compensation, and insufficient atomic-level uniformity of doping by using homologous molten salt-assisted gradient pre-calcination, thus eliminating the fluctuation of charge compensation effect between batches; it solves the problems of rare earth ion occupancy deviation, trap energy level broadening / annihilation, abnormal growth of hexagonal lattice anisotropic grains, and uncontrollable thermal quenching resistance by using strong magnetic field-assisted multi-temperature gradient sintering; and it solves the problems of powder surface lattice defects, nonradiative recombination caused by dangling bonds, and poor long-term environmental stability by using oxygen plasma in-situ surface passivation and annealing treatment, thus improving the long-term environmental stability of the powder. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation of phosphors in an embodiment of the present invention.

[0027] Figure 2 This is an X-ray diffraction pattern of the phosphor prepared in an embodiment of the present invention.

[0028] Figure 3 Mg in the embodiments of the present invention 4-x%-y% Ta2O9:x%RE 3+ ,y%M + Images of the phosphor under ultraviolet light and natural light. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0030] Example 1: A phosphor with multimode luminescence and resistance to thermal quenching, the phosphor material having the chemical composition of Mg. 4-x%-y% Ta2O9:x%RE 3+ ,y%M + In this context, RE represents any one of the four rare earth elements: Pr (praseodymium), Tb (terbium), Dy (dysprosium), and Tm (thulium), and M represents any one of the two alkali metal elements: Li (lithium) and Na (sodium).

[0031] In the rare earth activating ions doped with phosphor, x% are trivalent rare earth activating ions (REs). 3+ Replacement of Mg in the matrix 2+ The molar percentage of lattice sites is as follows: when RE is Pr, 0.2 ≤ x ≤ 2 (preferably x = 0.4); when RE is Tb, 0.1 ≤ x ≤ 5 (preferably x = 0.3); when RE is Dy, 1 ≤ x ≤ 6 (preferably x = 4); and when RE is Tm, 0.1 ≤ x ≤ 1.5 (preferably x = 0.1). In the phosphor-doped alkali metal ions, y% represents monovalent alkali metal charge-compensating ions M. + Replacement of Mg in the matrix 2+ The molar percentage of lattice sites, 1≤y≤9 (preferably y=5).

[0032] Example 2: A method for preparing a phosphor with multimode luminescence and thermal quenching resistance, used to prepare the multimode luminescence phosphor material as described in Example 1, comprising: Step S1. Preparation of supercritical fluid-assisted precursor: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3, and homologous MNO3 (molten salt medium) according to the material matching rule. The molar amount of MgO is (4 - x - y)·A, the molar amount of Ta2O5 is 2·A, the molar amount of RE2O3 is (x / 2)·A, the molar amount of M2CO3 is [(y - △y) / 2]·A, and the molar amount of homologous MNO3 (molten salt medium) is △y·A; where A represents the molar batching reference coefficient, with the unit of mol; △y is the proportional coefficient of the molar amount of M provided by the molten salt medium accounting for the total molar amount of M + and add them into a high-pressure reactor. Use anhydrous ethanol as an auxiliary dispersant, and the volume-mass ratio of anhydrous ethanol to all materials is 5 mL:1 g. Seal the reactor. + Then, use supercritical CO2 fluid to achieve ultra-fine dispersion and surface activation of the raw materials, and simultaneously complete the pre-decomposition of the precursor to obtain precursor powder; the specific steps are as follows: First, introduce high-purity CO2 gas (purity ≥ 99.9%) into the high-pressure reactor at a rate of 5 mL / min, heat up to 39 °C, adjust the pressure in the reactor to 9.8 MPa (to make CO2 reach the supercritical state), and maintain it for 32 min under an external ultrasound of 195 W, 40 kHz at a rotation speed of 290 rpm; then, maintain the supercritical state, heat up to 345 °C at a rate of 5 °C / min and increase the pressure to 24.5 MPa at a rate of 0.8 MPa / min, and keep the temperature and pressure constant for 1.1 h; finally, release the pressure to 4.5 MPa at a rate of 9.5 MPa / s and then release it to atmospheric pressure at a rate of 0.4 MPa / s to obtain a precursor powder without hard agglomeration and with nano-scale monodispersion.

[0033] Step S2. Gradient pre-calcination: Gradiently calcine the precursor powder in step S1 in a muffle furnace in the first-stage calcination, second-stage calcination, and third-stage calcination; among them, the first-stage calcination is specifically: in an atmospheric air atmosphere, heat up to 195 °C at a rate of 4.5 °C / min and keep the temperature constant for 1.1 h; the second-stage calcination is specifically: in an atmospheric air atmosphere, heat up to 345 °C at a rate of 4.5 °C / min and keep the temperature constant for 3.1 h; the third-stage calcination is specifically: in an atmospheric air atmosphere, heat up to 595 °C at a rate of 9.5 °C / min and keep the temperature constant for 2.1 h. During the calcination process, continuously introduce dry air with a flow rate of 20 sccm.

[0034]

[0035] ​Step S3, multi-temperature gradient sintering: First, press the pre-calcined powder into a blank (to ensure close contact between powder particles and improve solid-phase diffusion efficiency). Specifically, place the pre-calcined powder in a stainless steel mold and press it into a circular blank with a diameter of 20±1mm and a thickness of 3±0.5mm under a unidirectional pressure of 19.5MPa.

[0036] The green blank is then placed in a superconducting high magnetic field programmable sintering furnace, with the magnetic field direction perpendicular to the base surface of the green blank (i.e., the upper and lower end faces of the pressed green blank). The magnetic field strength of the superconducting high magnetic field programmable sintering furnace is 11.5T. Under normal atmospheric pressure and with the high magnetic field continuously activated, directional site-occupying pre-crystallization, trap energy level control, lattice crystallization, and trap locking are performed sequentially. Specifically, directional site-occupying pre-crystallization involves heating to 795℃ at a rate of 4.5℃ / min and holding for 4.1h. Trap energy level control involves heating to 1045℃ at a rate of 2.5℃ / min and holding for 6.1h. Lattice crystallization involves heating to 1245℃ at a rate of 4.5℃ / min and holding for 2.1h. The trap locking mechanism is as follows: first, the temperature is lowered to 895℃ at a rate of 1.8℃ / min and held for 3.1 hours; then, the temperature is lowered to 605℃ at a rate of 0.8℃ / min, and then cooled to room temperature along with the furnace. The strong magnetic field is maintained until the temperature drops below 595℃ and then shut off.

[0037] Step S4, Surface passivation: First, place the sintered green blank in an agate mortar for light grinding, and then pass it through a 300-mesh sieve to obtain fluorescent powder. Next, oxygen plasma treatment is performed, specifically as follows: First, the powder is evenly spread on a quartz tray (thickness ≤ 0.5 mm), placed in an RF plasma reaction chamber, and evacuated to a base pressure of 9 Pa; then, high-purity oxygen is introduced at a flow rate of 48 sccm and the chamber pressure is stabilized at 29 Pa; finally, a 13.56 MHz RF power supply is turned on and the power is adjusted to 48 W (low-energy mode to avoid etching of the powder surface and damage to the bulk structure), and the powder is treated at room temperature for 6 min (i.e., the powder is kept at room temperature throughout the process without high-temperature phase transition).

[0038] Step S5, Annealing: Immediately after the oxygen plasma treatment, the powder is placed in a programmable muffle furnace and annealed at 195°C for 32 minutes under normal air pressure. It is then allowed to cool naturally to room temperature to obtain the final product.

[0039] Example 3: A method for preparing a phosphor with multimode luminescence and thermal quenching resistance, used to prepare the multimode luminescence phosphor material as described in Example 1, comprising: Step S1. Preparation of supercritical fluid-assisted precursor: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3, and homologous MNO3 (molten salt medium) according to the material matching rule. The molar dosage of MgO is (4 - x - y)·A, the molar dosage of Ta2O5 is 2·A, the molar dosage of RE2O3 is (x / 2)·A, the molar dosage of M2CO3 is [(y - △y) / 2]·A, and the molar dosage of homologous MNO3 (molten salt medium) is △y·A; where A represents the molar batching reference coefficient with the unit of mol; △y is the proportional coefficient of the molar amount of M provided by the molten salt medium accounting for the total molar amount of M + and add them into a high-pressure reactor. Use anhydrous ethanol as an auxiliary dispersant, and the volume-mass ratio between anhydrous ethanol and all materials is 5.5 mL:1 g, then seal the reactor. + Then, use supercritical CO2 fluid to achieve ultra-fine dispersion and surface activation of the raw materials, and simultaneously complete the pre-decomposition of the precursor to obtain precursor powder; the specific steps are as follows: First, introduce high-purity CO2 gas (purity ≥ 99.9%) into the high-pressure reactor at a rate of 7.5 mL / min, heat up to 40°C, adjust the pressure in the reactor to 10 MPa (to make CO2 reach the supercritical state), and maintain it for 30 min under an external ultrasound of 200 W, 40 kHz at a rotation speed of 300 rpm; then, maintain the supercritical state, heat up to 350°C at a rate of 5.5°C / min and increase the pressure to 25 MPa at a rate of 0.9 MPa / min, and keep the temperature and pressure for 1 h; finally, release the pressure to 5 MPa at a rate of 10 MPa / s and then to atmospheric pressure at a rate of 0.45 MPa / s, and thus obtain the precursor powder without hard agglomeration and with nano-scale monodispersion.

[0040] Step S2. Gradient pre-calcination: Gradiently calcine the precursor powder in step S1 in a muffle furnace in the first-stage calcination, second-stage calcination, and third-stage calcination; specifically, the first-stage calcination is as follows: Under an atmospheric air atmosphere, heat up to 200°C at a rate of 5°C / min and keep the temperature for 1 h; the second-stage calcination is as follows: Under an atmospheric air atmosphere, heat up to 350°C at a rate of 5°C / min and keep the temperature for 2 h; the third-stage calcination is as follows: Under an atmospheric air atmosphere, heat up to 600°C at a rate of 10°C / min and keep the temperature for 2 h, and continuously introduce dry air with a flow rate of 25 sccm during the calcination process.

[0041] Step S3. Multi-temperature zone gradient sintering: First, press the pre-calcined powder into a green body (ensure close contact between powder particles to improve the solid-phase diffusion efficiency), specifically: Place the pre-calcined powder in a stainless-steel mold and press it into a circular green body with a diameter of 20 ± 1 mm and a thickness of 3 ± 0.5 mm under a unidirectional pressure of 20 MPa.

[0042] ​

[0043] The green blank is then placed in a superconducting high magnetic field controlled sintering furnace, with the magnetic field direction perpendicular to the base surface of the green blank (i.e., the upper and lower end faces of the pressed green blank). The magnetic field strength of the superconducting high magnetic field controlled sintering furnace is 11.7T. Under atmospheric pressure and air atmosphere, the high magnetic field is kept on throughout the process, and directional site-occupying pre-crystallization, trap energy level control, lattice crystallization, and trap locking are performed sequentially. Specifically, directional site-occupying pre-crystallization involves heating to 800℃ at a rate of 5℃ / min and holding for 4 hours. Trap energy level control involves heating to 1050℃ at a rate of 3℃ / min and holding for 6 hours. Lattice crystallization involves heating to 1250℃ at a rate of 5℃ / min and holding for 2 hours. Trap locking involves first cooling to 900℃ at a rate of 2℃ / min and holding for 3 hours; then cooling to 600℃ at a rate of 1℃ / min, followed by furnace cooling to room temperature, with the high magnetic field maintained until the temperature drops below 595℃ and then turned off.

[0044] Step S4, Surface passivation: First, place the sintered green blank in an agate mortar for light grinding, and then pass it through a 300-mesh sieve to obtain fluorescent powder. Next, oxygen plasma treatment is performed, specifically as follows: First, the powder is evenly spread on a quartz tray (thickness ≤ 0.5 mm), placed in an RF plasma reaction chamber, and evacuated to a base pressure of 9.5 Pa; then, high-purity oxygen is introduced at a flow rate of 50 sccm and the chamber pressure is stabilized at 30 Pa; finally, a 13.56 MHz RF power supply is turned on and the power is adjusted to 50 W (low-energy mode to avoid etching of the powder surface and damage to the bulk structure), and the powder is treated at room temperature for 5 min (i.e., the powder is kept at room temperature throughout the process without high-temperature phase transition).

[0045] Step S5, Annealing: Immediately after the oxygen plasma treatment, the powder is placed in a programmable muffle furnace and annealed at 200°C for 30 minutes under normal air pressure. It is then allowed to cool naturally to room temperature to obtain the final product.

[0046] Example 4: A method for preparing a phosphor with multimode luminescence and thermal quenching resistance, used to prepare the multimode luminescence phosphor material as described in Example 1, comprising: Step S1: Preparation of supercritical fluid-assisted precursors: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3, and homologous MNO3 (molten salt medium) according to the material matching rules. The molar amount of MgO is (4-xy)·A, the molar amount of Ta2O5 is 2·A, the molar amount of RE2O3 is (x / 2)·A, the molar amount of M2CO3 is [(y-△y) / 2]·A, and the molar amount of homologous MNO3 (molten salt medium) is △y·A; where A represents the molar basis coefficient in mol; △y is the amount of MNO3 provided by the molten salt medium. +The molar amount accounts for the total M + The proportionality coefficient of the molar amount, △y = k·y and it is forced to satisfy △y < y, k = 25%; and it is added into the high-pressure reactor. Absolute ethanol is used as the co-dispersant, and the volume-mass ratio between absolute ethanol and all materials is 6 mL:1 g. The reactor is sealed.

[0047] Then, supercritical CO2 fluid is used to achieve the superfine dispersion and surface activation of the raw materials, and the precursor pre-decomposition is completed synchronously to obtain the precursor powder; the specific steps are as follows: First, high-purity CO2 gas (purity ≥ 99.9%) is introduced into the high-pressure reactor at a rate of 10 mL / min, the temperature is raised to 41 °C, the pressure in the reactor is adjusted to 10.2 MPa (to make CO2 reach the supercritical state), and it is maintained for 28 min under an external ultrasound of 205 W and 40 kHz at a rotation speed of 310 rpm; then, maintaining the supercritical state, the temperature is raised to 355 °C at a rate of 6 °C / min and the pressure is raised to 25.5 MPa at a rate of 1 MPa / min, and it is kept at a constant temperature and pressure for 0.9 h; finally, the pressure is released to 5.5 MPa at a rate of 10.5 MPa / s and then to atmospheric pressure at a rate of 0.5 MPa / s, and the precursor powder body that is free of hard agglomeration and has nanoscale monodispersion is obtained.

[0048] Step S2, gradient pre-calcination: The precursor powder in Step S1 is subjected to gradient calcination of the first-stage calcination, the second-stage calcination, and the third-stage calcination in a muffle furnace in sequence; among them, the first-stage calcination is specifically as follows: Under an atmospheric air atmosphere, the temperature is raised to 205 °C at a rate of 5.5 °C / min and kept for 0.9 h; the second-stage calcination is specifically as follows: Under an atmospheric air atmosphere, the temperature is raised to 355 °C at a rate of 5.5 °C / min and kept for 2.9 h; the third-stage calcination is specifically as follows: Under an atmospheric air atmosphere, the temperature is raised to 605 °C at a rate of 10.5 °C / min and kept for 1.9 h, and dry air with a flow rate of 30 sccm is continuously introduced during the calcination process.

[0049] Step S3, multi-temperature zone gradient sintering: First, the pre-calcined powder body is pressed into a green body (ensuring close contact between powder particles and improving the solid-phase diffusion efficiency), specifically as follows: The pre-calcined powder body is placed in a stainless steel mold and pressed into a circular green body with a diameter of 20 ± 1 mm and a thickness of 3 ± 0.5 mm under a unidirectional pressure of 20.5 MPa.

[0050] The green blank is then placed in a superconducting high magnetic field programmable sintering furnace, with the magnetic field direction perpendicular to the base surface of the green blank (i.e., the upper and lower end faces of the pressed green blank). The magnetic field strength of the superconducting high magnetic field programmable sintering furnace is 12T. Under normal atmospheric pressure and with the high magnetic field continuously activated, directional site-occupying pre-crystallization, trap energy level control, lattice crystallization, and trap locking are performed sequentially. Specifically, directional site-occupying pre-crystallization involves heating to 805℃ at a rate of 5.5℃ / min and holding for 3.9h. Trap energy level control involves heating to 1055℃ at a rate of 3.5℃ / min and holding for 5.9h. Lattice crystallization involves heating to 1255℃ at a rate of 5.5℃ / min and holding for 1.9h. The trap locking mechanism is as follows: first, the temperature is lowered to 905℃ at a rate of 2.2℃ / min and held for 2.9h; then, the temperature is lowered to 605℃ at a rate of 1.2℃ / min, and then cooled to room temperature along with the furnace. The strong magnetic field is maintained until the temperature drops below 595℃ and then shut off.

[0051] Step S4, Surface passivation: First, place the sintered green blank in an agate mortar for light grinding, and then pass it through a 300-mesh sieve to obtain fluorescent powder. Next, oxygen plasma treatment is performed, specifically as follows: First, the powder is evenly spread on a quartz tray (thickness ≤ 0.5 mm), placed in an RF plasma reaction chamber, and evacuated to a base pressure of 10 Pa; then, high-purity oxygen is introduced at a flow rate of 52 sccm and the chamber pressure is stabilized at 31 Pa; finally, a 13.56 MHz RF power supply is turned on and the power is adjusted to 52 W (low-energy mode to avoid etching of the powder surface and damage to the bulk structure), and the powder is treated at room temperature for 4 min (i.e., the powder is kept at room temperature throughout the process without high-temperature phase transition).

[0052] Step S5, Annealing: Immediately after the oxygen plasma treatment, the powder is placed in a programmable muffle furnace and annealed at 205°C for 28 minutes under normal atmospheric pressure. It is then allowed to cool naturally to room temperature to obtain the final product.

[0053] Example 5: An anti-counterfeiting ink, using fluorescent powder prepared in any of Examples 2 to 4, includes fluorescent powder, acrylic resin, ethyl acetate, isopropanol, polyethylene wax, and dispersant (any one of Disperbyk-110, Solsperse20000, and DP-983), with mass fractions of 17.5–18.5%, 32.5–33.5%, 29.5–30.5%, 14.5–15.5%, 2–3%, and 1–2% (preferably 18%, 33%, 30%, 15%, 2.5%, and 1.5%). The specific preparation method is as follows: Mix the above raw materials in proportion (after the phosphor powder is prepared, grind it through a 200-mesh sieve, and then pulverize it using an air jet mill, controlling the phosphor powder D50 = 2-3 μm), stir at a speed of 300-500 rpm (preferably 400 rpm) for 4-6 minutes (preferably 5 minutes), then disperse it at high speed in a serrated disc dispersion disc (dispersion disc diameter: dispersion cylinder inner diameter is 1:3-4) at a speed of 1200-1500 rpm (preferably 1350 rpm) for 24-26 minutes (preferably 25 minutes); then, in an explosion-proof horizontal... The ink is ground using a sand mill (using 0.3mm zirconia beads) until the ink fineness is ≤5μm. The material temperature is controlled to ≤35℃ throughout the grinding process using a chiller to avoid high temperature damaging the phosphor crystal structure and causing luminescence performance degradation. Finally, the ground ink is first pre-filtered using a polypropylene (PP) meltblown filter with a pore size of 10-15μm (preferably 12μm or 13μm), and then finely filtered using a polytetrafluoroethylene (PTFE) filter with a pore size of 3-5μm (preferably 4μm) at a filtration pressure of 0.1-0.2MPa (preferably 0.15MPa) to obtain the final product.

[0054] Comparative Example 1: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursors: First, accurately weigh MgO, Ta2O5, RE2O3, and M2CO3 according to the material matching rules. The molar amount of MgO is (4-xy)·A, the molar amount of Ta2O5 is 2·A, the molar amount of RE2O3 is (x / 2)·A, and the molar amount of M2CO3 is (y / 2)·A; where A represents the molar basis coefficient in mol. Add the materials to a high-pressure reactor, using anhydrous ethanol as a dispersant. The volume-to-mass ratio of anhydrous ethanol to all materials is 5.5 mL: 1 g. Seal the reactor.

[0055] Then, supercritical CO2 fluid is used to achieve ultrafine dispersion and surface activation of the raw materials, and the precursor pre-decomposition is completed simultaneously to obtain precursor powder; the specific steps are the same as step S1 in Example 3.

[0056] Step S2, gradient pre-calcination: consistent with step S2 in Example 3.

[0057] Step S3, multi-temperature gradient sintering: consistent with step S3 in Example 3.

[0058] Step S4, Surface passivation: Same as step S4 in Example 3.

[0059] Step S5, Annealing: Same as step S5 in Example 3.

[0060] Comparative Example 2: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursor: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3, and homologous MNO3 (molten salt medium) according to the material matching rules. The specific formula is the same as in step S1 of Example 3. Add them to an agate mortar, use anhydrous ethanol as a dispersant, and the volume-to-mass ratio of anhydrous ethanol to all materials is 5.5mL:1g. Grind and mix evenly under the conditions of room temperature and relative humidity ≤60% (generally grind and mix for 30-40min) until the ethanol is completely evaporated and the powder is in a uniform dry powder state. The precursor powder is obtained by monitoring D50 ≤2μm with a laser particle size analyzer.

[0061] Step S2, gradient pre-calcination: consistent with step S2 in Example 3.

[0062] Step S3, multi-temperature gradient sintering: consistent with step S3 in Example 3.

[0063] Step S4, Surface passivation: Same as step S4 in Example 3.

[0064] Step S5, Annealing: Same as step S5 in Example 3.

[0065] Comparative Example 3: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursor: consistent with step S1 in Example 3.

[0066] Step S2, Pre-calcination: The precursor powder from step S1 is heated to 600℃ in a muffle furnace under normal pressure and air atmosphere at a rate of 5 / min and held for 5h. During the calcination process, dry air with a flow rate of 25sccm is continuously introduced.

[0067] Step S3, multi-temperature gradient sintering: consistent with step S3 in Example 3.

[0068] Step S4, Surface passivation: Same as step S4 in Example 3.

[0069] Step S5, Annealing: Same as step S5 in Example 3.

[0070] Comparative Example 4: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursor: consistent with step S1 in Example 3.

[0071] Step S2, gradient pre-calcination: consistent with step S2 in Example 3.

[0072] Step S3, multi-temperature gradient sintering: First, press the pre-calcined powder into a blank (to ensure close contact between powder particles and improve solid-phase diffusion efficiency). Specifically, place the pre-calcined powder in a stainless steel mold and press it into a circular blank with a diameter of 20±1mm and a thickness of 3±0.5mm under a unidirectional pressure of 20MPa.

[0073] Under normal atmospheric pressure, directional site pre-crystallization, trap energy level control, lattice crystallization, and trap locking were performed sequentially. Specifically, directional site pre-crystallization involved heating to 800℃ at a rate of 5℃ / min and holding for 4 hours. Trap energy level control involved heating to 1050℃ at a rate of 3℃ / min and holding for 6 hours. Lattice crystallization involved heating to 1250℃ at a rate of 5℃ / min and holding for 2 hours. Trap locking involved cooling to 900℃ at a rate of 2℃ / min and holding for 3 hours; then cooling to 600℃ at a rate of 1℃ / min, followed by furnace cooling to room temperature.

[0074] Step S4, Surface passivation: Same as step S4 in Example 3.

[0075] Step S5, Annealing: Same as step S5 in Example 3.

[0076] Comparative Example 5: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursor: consistent with step S1 in Example 3.

[0077] Step S2, gradient pre-calcination: consistent with step S2 in Example 3.

[0078] Step S3, Sintering: First, press the pre-calcined powder into a blank (to ensure close contact between powder particles and improve solid-phase diffusion efficiency). Specifically, place the pre-calcined powder in a stainless steel mold and press it into a circular blank with a diameter of 20±1mm and a thickness of 3±0.5mm under a unidirectional pressure of 20MPa.

[0079] The green blank is then placed in a superconducting high magnetic field programmable sintering furnace with the magnetic field direction perpendicular to the base surface of the green blank (i.e., the upper and lower end surfaces of the pressed green blank). The magnetic field strength of the superconducting high magnetic field programmable sintering furnace is 11.7T. Under normal atmospheric pressure, the high magnetic field is turned on throughout the process. The temperature is first raised to 1250℃ at a rate of 5℃ / min and held for 12 hours. Then, the temperature is lowered to 600℃ at a rate of 2℃ / min. Subsequently, the furnace is cooled to room temperature. The high magnetic field is maintained until the temperature drops below 595℃ and then turned off.

[0080] Step S4, Surface passivation: Same as step S4 in Example 3.

[0081] Step S5, Annealing: Same as step S5 in Example 3.

[0082] Comparative Example 6: A method for preparing a phosphor, comprising: Step S1, preparation of supercritical fluid-assisted precursor: consistent with step S1 in Example 3.

[0083] Step S2, gradient pre-calcination: consistent with step S2 in Example 3.

[0084] Step S3, multi-temperature gradient sintering: consistent with step S3 in Example 3.

[0085] Step S4, Annealing: First, the sintered green blank is placed in an agate mortar and lightly ground, then passed through a 300-mesh sieve to obtain fluorescent powder; then the fluorescent powder is annealed by placing the powder in a programmable muffle furnace and holding it at 200°C for 30 minutes under normal air pressure for low-temperature annealing; then it is naturally cooled to room temperature to obtain the final product.

[0086] The phosphors prepared in Examples 2-4 and Comparative Examples 1-6 were tested for ultraviolet excitation internal quantum efficiency, X-ray excitation light yield, long afterglow duration, thermoluminescence cycling stability, and thermal quenching resistance. The test environments in Examples 2-4 and Comparative Examples 1-6 were completely consistent. The ultraviolet excitation internal quantum efficiency test method was in accordance with GB / T 44454-2024. The final internal quantum efficiency (QY) was: ; In the formula: This represents the excitation spectrum measured on the reference sample. This represents the emission spectrum measured on the sample; The X-ray excitation light yield was determined using the standard reference relative calibration method (compliant with IEC 61948-2:2007 scintillator testing standard). A commercially available standard scintillator single crystal with known light yield was used as a reference. Under completely identical X-ray excitation and optical path acquisition conditions, the luminous integral intensity of the test sample and the reference sample were compared to calculate the absolute light yield of the test sample.

[0087] Long-lasting afterglow time refers to the time after the sample has been saturated with the excitation source, and excitation has stopped, recording the decay curve of the afterglow brightness over time. The minimum brightness threshold that is perceptible to the human eye (e.g., the industry standard of 0.32 mcd / m²) is used. 2 The endpoint is recorded as the total time from the cessation of excitation to the brightness decreasing to the threshold.

[0088] Thermoluminescence cycle stability is determined by testing the rate of decay of the thermoluminescence integral intensity in each cycle through a standardized cycle process of "UV saturation excitation - thermoluminescence reading - annealing and clearing". The maximum number of cycles with "main emission peak integral intensity decay ≤ 10%" (i.e. intensity retention rate ≥ 90%) is used as the cycle stability index.

[0089] Thermal quenching resistance is determined by using a thermal quenching analysis system with 254 nm (or other wavelengths mentioned above) as the excitation wavelength to test the relative brightness of the sample at room temperature (298 K), i.e., using the steady-state luminescence intensity at room temperature as the reference. Then, the sample is placed in a constant temperature sample chamber at 523 K (250 °C), and the relative brightness of the sample is tested again. The ratio of the high-temperature intensity to the room temperature reference intensity is calculated, which is the thermal quenching resistance of the relative brightness.

[0090] The specific test results are shown in the table below:

[0091] As can be clearly seen from the table above, the phosphor prepared by the present invention through specific steps has high quantum efficiency in ultraviolet excitation, high X-ray excitation light yield, long afterglow duration, good thermoluminescence cycle stability, and excellent anti-quenching performance. It is suitable for large-scale industrial production and can be widely used in many fields such as advanced anti-counterfeiting, information encryption, radiation detection, and emergency lighting.

Claims

1. A phosphor with multimode luminescence and resistance to thermal quenching, characterized in that: The chemical composition of this phosphor material is Mg. 4-x%-y% Ta2O9:x%RE 3+ In this context, RE represents any one of the four rare earth elements Pr, Tb, Dy, and Tm, and M represents any one of the two alkali metal elements Li and Na.

2. The phosphor with multimode luminescence and thermal quenching resistance according to claim 1, characterized in that: x% represents trivalent rare earth activated ions (RE). 3+ Replacement of Mg in the matrix 2+ The molar percentage of lattice sites is 0.2 ≤ x ≤ 2 when RE is Pr, 0.1 ≤ x ≤ 5 when RE is Tb, 1 ≤ x ≤ 6 when RE is Dy, and 0.1 ≤ x ≤ 1.5 when RE is Tm; y% of the phosphor-doped alkali metal ions represents monovalent alkali metal charge-compensating ions M. + Replacement of Mg in the matrix 2+ The molar percentage of lattice sites, 1≤y≤6.

3. A method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 1 or 2, characterized in that: include: Step S1, preparation of supercritical fluid-assisted precursor: First, accurately weigh MgO, Ta2O5, RE2O3, M2CO3 and homologous MNO3 according to the material matching rules, and add them to the high-pressure reactor. Use anhydrous ethanol as a dispersant and seal the reactor. Then, supercritical CO2 fluid is used to achieve ultrafine dispersion and surface activation of the raw materials, and the precursor pre-decomposition is completed simultaneously to obtain precursor powder; Step S2, gradient pre-calcination: The precursor powder from step S1 is subjected to gradient calcination in a muffle furnace, consisting of a first stage of calcination, a second stage of calcination, and a third stage of calcination. Step S3, multi-temperature gradient sintering: First, the pre-calcined powder is pressed into a green blank; then the green blank is placed in a superconducting high magnetic field programmable sintering furnace with the magnetic field direction perpendicular to the green blank base surface. Under normal air pressure, the high magnetic field is turned on throughout the process to sequentially carry out directional site occupancy pre-crystallization, trap energy level control, lattice crystallization and trap locking. Step S4, Surface passivation: First, grind the sintered green blank, and then perform oxygen plasma treatment; Step S5, Annealing treatment: The powder after oxygen plasma treatment is annealed and then naturally cooled to room temperature to obtain the final product.

4. The method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 3, characterized in that: In step S1, the molar amount of MgO is (4-xy)·A, the molar amount of Ta2O5 is 2·A, the molar amount of RE2O3 is (x / 2)·A, the molar amount of M2CO3 is [(y-Δy) / 2]·A, and the molar amount of homologous MNO3 is Δy·A; where A represents the molar basis coefficient for the proportioning of MgO, in mol; and Δy represents the amount of MgO provided by the molten salt medium. + The molar amount accounts for the total M + The proportionality constant of molar quantities, Δy = k·y, and is required to satisfy Δy <y,k=15%~25%。 5. A method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 3 or 4, characterized in that: In step S1, the volume-to-mass ratio of anhydrous ethanol to all materials is 5-6 mL: 1 g.

6. A method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 4 or 5, characterized in that: In step S1, supercritical CO2 fluid is used to achieve ultrafine dispersion and surface activation of the raw materials, and the precursor pre-decomposition is completed simultaneously to obtain precursor powder. The specific steps are as follows: First, high-purity CO2 gas is introduced into the high-pressure reactor at a rate of 5-10 mL / min, the temperature is raised to 39-41℃, the pressure inside the reactor is adjusted to 9.8-10.2 MPa, and the reaction is carried out at a rotation speed of 290-310 rpm, 195-205 W, and 40 kHz using an external ultrasonic generator. The temperature is maintained at 28–32 min; then, the supercritical state is maintained, and the temperature is increased to 345–355℃ at 5–6℃ / min and the pressure is increased to 24.5–25.5MPa at 0.8–1MPa / min, and the temperature and pressure are maintained for 0.9–1.1 h; finally, the pressure is released to 4.5–5.5MPa at 9.5–10.5MPa / s and then released to atmospheric pressure at 0.4–0.5MPa / s, thus obtaining a precursor powder without hard agglomerates and with nanoscale monodispersity.

7. The method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 3, characterized in that: In step S2, the first stage of calcination specifically involves heating to 195–205°C at a rate of 4.5–5.5°C / min under normal air pressure and holding for 0.9–1.1 h; the second stage of calcination specifically involves heating to 345–355°C at a rate of 4.5–5.5°C / min under normal air pressure and holding for 2.9–3.1 h; the third stage of calcination specifically involves heating to 595–605°C at a rate of 9.5–10.5°C / min under normal air pressure and holding for 1.9–2.1 h, with dry air continuously introduced at a flow rate of 20–30 sccm during the calcination process.

8. The method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 3, characterized in that: In step S3, pressing the pre-calcined powder into a blank specifically involves placing the pre-calcined powder in a stainless steel mold and pressing it into a circular blank with a diameter of 20±1mm and a thickness of 3±0.5mm under a unidirectional pressure of 19.5~20.5MPa.

9. The method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 8, characterized in that: In step S3, the magnetic field strength of the superconducting high magnetic field programmable sintering furnace is 11.5-12T; the directional site-occupying pre-crystallization is specifically: the temperature is raised to 795-805℃ at a rate of 4.5-5.5℃ / min and held for 3.9-4.1h.

10. The method for preparing a phosphor with multimode luminescence and thermal quenching resistance according to claim 3, characterized in that: In step S4, the sintered blank is placed in an agate mortar for light grinding and passed through a 300-mesh sieve to obtain fluorescent powder. The oxygen plasma treatment process is as follows: First, the powder is evenly spread on a quartz tray and placed in a radio frequency plasma reaction chamber. The chamber is then evacuated to a background pressure of 9–10 Pa. Next, high-purity oxygen is introduced at a flow rate of 48–52 sccm and the chamber pressure is stabilized at 29–31 Pa. Finally, a 13.56 MHz radio frequency power supply is turned on and the power is adjusted to 48–52 W. The treatment is carried out at room temperature for 4–6 minutes.

Images